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Learning and memory in adolescent psychiatric inpatients with major depression: A normative study of the California verbal learning test
Pergamon
Archives of Clinical Neuropsychology,Vol. 12, No. 6, pp. 575 584, 1997 Copyright © 1997 National Academy of Neuropsychology Printed in the USA. All rights reserved 0887-6177/97 $17.00 + .00
PII S0887-6177(97)00012-7
Learning and Memory in Adolescent Psychiatric Inpatients with Major Depression: A Normative Study of the California Verbal Learning Test William P. Horan Four Winds Research Foundation
David L. Posse and Susan R. Borgaro Fairleigh Dickinson University and Four Winds Research Center
John M. Stokes Pace University
Philip O. Harvey Mt. Sinai School of Medicine
Depressed adults have deficits in memory functions, especially on demanding tasks, but few studies of depressed adolescents have been published. In order to examine the extent of memory impairment and its diagnostic specificit',; adolescent inpatients with DSM-III-R diagnoses of Major Depression (n = 56), Conduct Disorder (n = 42), or mixed Depression and Conduct Disorder (n = 22) were tested on the California Verbal Learning Test (CVLT) and compared to each other, to CVLT norms, and ta previously published CVLT norms for adults with Major Depression. Adolescents with Major Depression performed below normative standards on all aspects of the CVLT, but did not have a specific profile of memory impairments that was different f~'om the two comparison samples. Relative to norms for adult patients with Major Depression, adolescent females under performed across all CVLT measures, but males did not differ from adults Depression in adolescence is not associated with specific memory impairments, but adolescent females with depression may have more severe de/~cits than depressed adults. © 1997 National Academy of Neurop.~\vchology. Published by EIsevier Science Ltd
This research was supported by a grant from the National Institute of Drug Abuse to Dr. Posse. The authors would like to thank Drs. Joel Lord, Oscar Tanaka, and David Medoff for their assistance. William P. Horan is now at the University of New Mexico. Address correspondence to: Philip D. Harvey, Department of Psychiatry, Box 1229, Mt. Sinai School of Medicine, New York, NY 10029; E-mail: [email protected]. © 1997 National Academy of Neuropsychology. Published'by Elsevier Science Ltd
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Impairments in learning and memory have been extensively studied in depressed adults. A substantial body of literature has shown both quantitative and qualitative changes in the processing of verbal material in patients with depression. Various components of memory and learning have been implicated, including short-term memory (STM; Breslow, Kocsis, & Belkin, 1980; Colby & Gotlib, 1988; Richards & Ruff, 1989), long-term memory (LTM; Whitehead, 1974), and the transfer of information from STM to LTM (Henry, Weingartner, & Murphy, 1973; Krames & McDonald, 1985). In some studies the severity of depressive symptoms appears to be positively correlated with the degree of memory impairment found (Cohen, Weingartner, Smallberg, Pickar, & Murphy, 1982; Henry et al., 1973). Depressionrelated impairments are not simply attributable to a lack of motivation (Richards & Ruff, 1989) and have been shown to abate with remission of depressive symptoms in response to somatic and psychotherapeutic interventions (e.g., Cronholm & Ottoson, 1961; Stromgren, 1977), suggesting that these cognitive impairments are state-dependent features of depression. Performance deficits found in depressed adults have typically been on tasks using neutrally valenced material and requiring effortful cognitive processing (e.g, immediate recall, delayed recall, list learning). In fact, considerable evidence supports the hypothesis that depression interferes with tasks requiring effortful processing, but only minimally interferes with automatic processing tasks (e.g., frequency encoding, spatial location encoding: Hartlage, Alloy, Vazquez, & Dykman, 1993; Weingartner, 1986; Weingartner, Cohen, Bunney, Ebert, & Kaye, 1982; Weingartner, Burns, Diebel, & LeWitt, 1984). Deficiencies in effort-demanding processing strategies have been found in depressed patients, including poor use of encoding strategies (Cohen, 1982; Roy-Byrne, Weingartner, Bierer, Thompson, & Post, 1986), reduced levels of organization at encoding (Cohen et al., 1982; Weingartner, 1986), and reductions in recall memory (Colby & Gotlib, 1988; Krames & McDonald, 1985). In fact, Hartlage et al. (1993) proposed that this pattern of cognitive impairment may be specific to depression, as compared to other psychiatric disorders. The frequency with which these impairments have been found has led researchers to call for norms to understand the performance of depressed individuals. Otto et al. (1994) recently published normative data for depressed adults on the California Verbal Learning Test (CVLT), a widely used clinical measure of verbal learning and memory. They found that depressed outpatients performed between one half to one standard deviation below normative standards from the CVLT manual. These impairments affected men and women equally, were apparent after controlling for the effects of education, and were not associated with the severity of depression. Despite substantial evidence that depressive disorders in adolescence are phenomenologically similar to depressive disorders in adults (e.g., Poznanski, 1982), the characteristics of memory functioning in major depression and the correlations between severity of depression and level of memory impairment in adolescence remains unclear. No studies investigating the performance of adolescent patients with major depression have yet been published. In this study, verbal learning and memory were studied with the CVLT in adolescent inpatients diagnosed with Major Depressive Disorder, as well as comparison groups with Conduct Disorder and the dual diagnosis of Major Depression and Conduct Disorder. It was predicted that depressed adolescents, like adults with Major Depression, would perform poorly relative to normative standards for the CVLT. There were no specific predictions regarding the performance of adolescent patients with Conduct Disorder or the interaction of Conduct Disorder and Major Depression. If deficits in certain components of memory functioning were specific to depression it would be expected that patients with Major Depression would underperform relative to comparison subjects without depression. This study also sought to compare the level of impairment found in depressed adolescents to that previously seen in
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depressed adults in the Otto et al. (1994) study. Thus, the study examines memory functioning in adolescent Major Depression, both in terms of diagnostic specificity and severity compared to adult norms for normal and depressed individuals.
METHODS Participants Participants in this study were consecutive admissions to adolescent inpatient units of a private psychiatric hospital. All were recruited within 1 week of admission and their assent to participate was solicited, followed by parental informed consent. They were interviewed with the Structured Clinical Interview for DSM-111-R (SCID; Spitzer, Williams, Gibbon, & First, 1990) by a trained interviewer and a comprehensive chart review was performed. This comprehensive chart review included the use of the specific DSM-III-R criteria for Conduct Disorder in checklist form, since the SCID does not have specific modules for this diagnosis. DSM-III-R diagnoses were generated by the interviewer and cross-checked by one of the authors (PDH). In order to document the reliability of the diagnostic process, two raters performed 50 diagnostic interviews and chart reviews simultaneously. One rater performed the interview and both raters generated diagnostic ratings. Of the total of 73 psychiatric diagnoses obtained with this procedure, the raters disagreed on 4, resulting in a Kappa coefficient of .89 (p < .001). Raters also generated a Global Assessment of Functioning (GAF) score on the basis of the information collected in the assessment. This score ranges from I to 100 and measures global adjustment, including psychiatric symptoms and adaptive functions. Lower scores indicate poorer functioning. The interrater reliability (lntraClass correlation) was .98 for the 50 overlapping GAF scores. Depressed subjects were included in the present study only if they received a DSM-111-R diagnosis of Major Depressive Disorder. Subjects meeting criteria for other depressive disorders (Dysthymic Disorder, Depression NOS) were excluded, in order to increase the homogeneity of subjects within the depressed group. Since a goal of this research was to examine the specificity of verbal learning and memory impairments to depression, comparison groups of adolescents diagnosed with Conduct Disorder or both Major Depressive Disorder and Conduct Disorder were also studied. No subjects had a Bipolar Disorder diagnosis. While five of the Major Depression patients had a secondary diagnosis of an anxiety disorder, none of the patients in the other two groups had a secondary diagnosis in the anxiety disorder domain. Six depressed patients had an eating disorder diagnosis and two patients in the Conduct Disorder group and none of the mixed group had an eating disorder diagnosis. The prevalence of substance abuse disorder diagnoses was considerably higher and is presented, along with other descriptive information, in Table 1. Substance abuse as rated in this study included abuse of or dependence on either alcohol or cannabis, as determined by the SCID interview. All subjects with a Wechsler Full-Scale IQ score of less than 80 were excluded, as were all subjects who were uncooperative with testing on any of the cognitive measures. Further exclusion criteria included any subject with an acquired or developmental neurological disorder, including developmental learning disorders, seizure disorders, or history of disease or trauma involving the brain. Materials and Design California Verbal Learning Test (CVLT). The CVLT (Delis, Kramer, Kaplan, & Ober, 1987) consists of five serial verbal presentations of a 16-item word list (List A: "Monday's
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W. P. Horan et al. TABLE 1 Demographic Data on All Subjects
Depressed N Age % Male BDI scorea Verbal IQ WRAT-R reading subtest % Substance abuse Global assessment of functioning (GAF)b
56 15.13 (I.61) 31% 21.26(11.07) 104.46(14.07) 104.89(13.85) 16% 51.38(10.32)
Diagnostic Group Conduct Disordered 42 15.28 (1.20) 64% 9.55 (8.38) 98.93(11.97) 103.96(14.09) 54% 50.80(14.26)
Mixed 22 14.86 (1.32) 45% 15.15 (9.61) 96.23 (9.01) 101.78(14.82) 30% 51.08 (7.08)
Note. Standard deviations are in parentheses. aHigher scores reflect more severe impairment. bLower scores reflect poorer functioning.
shopping list") composed of items semantically related to four common categories. Following each presentation, testees are asked to recall as many items as they can in any order. After the fifth learning trial, a second list (List B: "Tuesday's shopping list"), also consisting of four items from each of four semantic categories, is presented once. After recalling List B, the testee is asked to recall List A (Short Delay), first without (Free Recall) and then with semantic cues. Then there is a delay period of 20 minutes. After the delay, the testee is again asked to recall items from List A, first without and then with semantic cues, after which a recognition trial is administered. There are multiple dependent variables derived from the CVLT. In the current study, the variables examined are trial 1 recall, total learning over trials 1 to 5, list A, trial 5 recall, list B recall, and long and short delayed free and cued recall.
Beck Depression Inventory. All patients completed the Beck Depression Inventory-long form (BDI; Beck, Ward, Mendelson, Mock, & Erbaugh, 1961). The BDI contains 21 items on which the patient provides self-reports in response to statements regarding the severity of depression on a 4-point (0-3) scale. The dependent variable used was the total score. Wide-Range Achievement Test-Revised (WRAT-R) word recognition subtest. As a portion of their psychological evaluation at the hospital, all participants were examined with the Wide-Range Achievement Test-Revised (WRAT-R; Jastrak, 1984). This subtest requires participants to read a list of words of ascending difficulty, with one point given for each correct pronunciation of the words. Scores can be converted either to grade or "standardized" IQ-equivalent scores. In order for these scores to be compared to the participants' obtained verbal IQs to examine academic under performance relative to estimated intelligence, the IQ-equivalent scores were calculated and used as the dependent variable.
Procedure Participants were assessed with the SCID within 2 days of their recruitment into the project, which occurred within 7 days of their admission to the hospital. After SCID assessment, they were given the research testing battery, including the CVLT, in a single testing session. Since all adolescent patients in the setting where this research was conducted undergo comprehensive psychological testing for purposes of clinical assessment, the verbal IQ, reading, and BDI data were extracted from their clinical chart.
Memory in Adolescent Depression
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Data Analysis Since the normative data for the CVLT were established in neurologically intact individuals aged 17 to 34 years, the applicability of the normative data to the present sample (M age 15.2) was examined statistically. The performance of participants who were over 17, and hence "old enough" to be administered the CVLT was compared to younger ones. A 3 (diagnostic group) x 2 (age 17 vs. less than 17) MANCOVA, with Verbal IQ as the covariate, was performed on the CVLT variables examined in this study. Results of this analysis revealed no main effects for age, F(2, 113) = .830, p > .05, and no group x age interaction effect, F(2, 113) = 1.08, p > .05. Therefore, no statistically significant differences were obtained on the CVLT scores between participants aged 17 (n = 22), and those aged less than 17 years (n = 98), suggesting that the task is not too difficult for the younger participants. To allow for comparison between patient groups and normative data, raw scores were transformed to standard scores according to the norms provided in the CVLT manual. All scores are z-scores other than the Total Recall, trials 1 to 5 score, which is a T-score.
RESULTS The patient samples were compared on their Verbal IQ scores, WRAT-R word recognition scores, and BDI total scores with analysis of variance (ANOVA). There was a significant group difference in VIQ, F(2, 118) = 4.10, p < .05. Tukey post hoc tests found only one significant group difference: that the patients with major depression had significantly higher scores than patients with a diagnosis of both conduct disorder and major depression. There was also a significant overall difference in BDI scores, F(2, 118) = 7.02, p < .001. Tukey post hoc tests revealed that the only significant group difference was a significantly higher score in the major depression patients compared to the conduct disorder group. There were no group differences in WRAT-R reading scores, however, F(2, 118) = 1.46, p > .05. The gender distributions of the samples were compared with chi-square tests, finding a significant overall difference ×2(2) = 12.08, p < .005. There were more females in the two groups with depression and more males in the pure Conduct Disorder group. Performance on all of the CVLT variables for the three groups is presented in Table 2. T-tests were computed to compare substance abusers and nonabusers on each of the CVLT scores. None of these analyses found a significant difference [all t(l18) < 1.45, all p > .15]. Additional t-tests were computed to compare medicated versus nonmedicated patients on each of the CVLT scores. None of these analyses found a significant difference [all t(118) < 1.18, all p > .24]. The first principal analysis of CVLT performance was a 2 (Gender) x 3 (Diagnosis) Multivariate analysis of variance (MANOVA) for all of the CVLT variables. These analyses were performed on the T or standard scores. There was no overall difference between the diagnostic groups, Wilks Lambda = .88, Pillais Approx. F(18, 208) = .74, p = .77 and none of the univariate effects were significant either. There were no significant Gender effects, Wilks lambda -- .91, Pillais Approx. F(9, 103) -- 1.14, p = .34, with no univariate effects significant either. Finally, the Gender x Diagnosis interaction was also nonsignificant, Wilks lambda -- .89, Pillais Approx F(18, 208) -- .68, p -- .83. No Univariate interactions were significant. As a result, the data presented in Table 2 are not broken down by gender. Since the groups differed significantly in VIQ, the MANOVA was repeated with a multivariate analysis of covariance (MANCOVA), with VIQ as the covariate. Significant [all t(l18) > 4.91, all p < .001] covariate effects were found for all CVLT variables other than recognition hits, t(118) = .90, p = .37. However, none of the multivariate diagnostic group or gender main
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TABLE 2 Group Means Across CVLT Variables
Depressed
Total Recall 1-5 List A, Trial 1 List A, Trial 5 List B Recall SD Free Recall SD Cued Recall LD Free Recall LD Cued Recall Recognition Hits
Diagnostic Group Conduct Disordered
Mixed
Raw
Standard
Raw
Standard
Raw
Standard
52.59 (8.62) 7.09 (2.08) 12.17 (1.99) 6.50 (1.68) 11.41 (2.29) 11.56 (2.33) 11.02 (2.58) 11.63 (2.52) 14.63 (1.23)
33.93 (13.81) - 1.17 (1.24) -2.46 (1.60) -.87 (.83) - 1.33 (1.29) - 1.80 (1.29) -2.02 (1.47) -2.02 (1.47) - 1.67 (1.59)
51.90 (8.85) 7.12 (1.98) 12.00 (2.43) 6.43 (1.74) 10.69 (2.53) 11.45 (2.56) 10.95 (2.65) 11.50 (2.44) 14.52 ( 1.58)
36.05 (14.22) -.98 (I.07) -2.14 (I .90) -.67 (.95) - 1.40 (1.45) - 1.55 ( 1.60) -1.60 ( 1.50) - 1.79 (1.51) - 1.64 (1.76)
53.57 (8.89) 7.33 (2.22) 12.52 (2.09) 6.14 (2.63) 10.67 (2.15) 10.73 (4.80) 10.32 (4.90) 10.68 (4.90) 13.59 (5.23)
36.81 (15.09) - 1.0 (1.26) -2.05 (1.94) -.95 (1.40) - 1.57 (1.29) - 1.57 (1.17) -1.86 (1.46) - 1.81 ( 1.54) - 1.52 ( 1.69)
Note. Only the Total Recall, trials 1-5 is a t-score, all other standard scores are z-scores; standard deviations are
presented in parentheses. SD = Short Delay; LD = Long Delay.
effects or t w o - w a y interactions w e r e altered by the use o f V I Q as a covariate. In the next analysis, Pearson correlations w e r e c o m p u t e d b e t w e e n each of the C V L T variables and B D I total scores and G A F scores. N o n e o f the correlations w e r e significant (all r < .20, all p > .O6). The p e r f o r m a n c e of the depressed adolescents was c o m p a r e d to the n o r m a t i v e standards of the C V L T Research manual, with these c o m p a r i s o n s p e r f o r m e d separately with t-tests for males and females. Patients consistently u n d e r p e r f o r m e d on all variables, with all scores for all groups on all variables, other than list B recall, found to be 1 or m o r e S D b e l o w n o r m a t i v e standards. The only nonsignificant c o m p a r i s o n was for list B recall for the male patients with m i x e d depression and conduct disorders, t(8) = 1.67, p < . 10. All other t values w e r e > 2 . 1 2 , all p < .05. In the final analysis, the C V L T p e r f o r m a n c e of the depressed adolescents was c o m p a r e d to the p r e v i o u s study o f depressed adults. T h e s e analyses were p e r f o r m e d separately by gender, because o f the gender-specific C V L T norms, and the analyses e x c l u d e d the cuedrecall variables, w h i c h w e r e not collected in the Otto et al. (1994) n o r m a t i v e study o f adult patients. T-tests w e r e used to c o m p a r e the p e r f o r m a n c e o f the current sample o f adolescents with m a j o r depression to the p r e v i o u s l y published adult norms. As presented in Table 3, the f e m a l e adolescent patients p e r f o r m e d m o r e poorly than the f e m a l e adult patients on each o f the C V L T variables. In the m a l e subjects, significant differences were found only for List A, trial 5 p e r f o r m a n c e and long-delay free recall, with adolescent patients p e r f o r m i n g m o r e poorly.
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TABLE 3
Comparison of Depressed Adolescent Patients and the Norms for Depressed Adults Depressed Females
Depressed Males
Total Recall, Trials 1 5 List A, Trial 1 List A, Trial 5 List B Recall Short-Delay Free Recall Long-Delay Free Recall Long-Delay Recognition
Adolescents
Adults
t-Values
Adolescents
Adults
t-Values
37.31 (16.29) -.81 (1.38) -2.38 (1.75) -.69 (.79) - 1.13 ( 1.71 ) 1.75 (1.44) 1.50 ( 1.55)
42.20 (15.21) .87 (.98) -.89 (2.04) -.23 (I.15i -.47 (1.30) -.75 ( 1.38l -.92 ( 1.75 )
1.19
32.50 (12.59) -1.32 (1.16) 2.50 (1.55) -.95 (.84) - 1.92 ( 1.08) -2.13 (1.40) - 1.74 (1.62)
41.6 (13.21 -.77 (1.14) -1.12 (1.64) -.52 (1.14) -.62 ( 1.53 ) -.92 ( 1.51 ) -.59 (1.42)
3.49***
19 2.66** 1.48 1.69 2.56* 1.21
2.39** 4.31"** 2.05* 4.64*** 4.64*** 3.83***
Note. Only the Total Recall, Trials 1-5 is a t-score, all other standard scores are :-scores; z-scores are in parentheses, *p "< .05; **p < .01; ***p < .001.
DISCUSSION Depressed adolescent patients were found to perform significantly more poorly than normative data for the CVLT. However, these impairments were not observed to be specifically related to depression. Rather, a general verbal learning and memory impairment was observed across the different groups of adolescent inpatients. The magnitude of impairment of these patients was substantial, with patients in all groups performing -<1 SD below normative standards on average across all variables other than list B learning. Male adolescent inpatients performed as poorly as normative standards for adults with major depression, while female adolescent inpatients performed more poorly than the depressed female patients in the previous normative sample. Methodological limitations in the current study should be considered before interpreting these results. The lack of a comparison sample of normal adolescents limits the extent to which conclusions may be drawn concerning the verbal learning and memory abilities of the adolescents examined in this study. Adolescent norms for the CVLT are currently lacking and would be useful. Analyses revealed no significant differences between adolescents aged 17 years and less than 17 on any of the CVLT variables examined, suggesting that the impairments observed are not simply attributable to this test being overly challenging for this younger population. Additional limitations include the fact that a proportion of the subjects in this sample were medicated or had a recent history of substance abuse. However, no differences were observed between substance abusing versus non-abusing, or medicated versus nonmedicated patients, suggesting that these/'actors did not significantly influence the results of cognitive testing in this study. A final limitation is the small sample size of the mixed conduct disorder and depression group. Since this group is so small, interpretations regarding characteristics of the overlap between conduct disorder and depression should not be drawn from this study. Several of the factors that have been proposed to mediate the relationship between depression and memory performance also did not appear to account for the lack of a specific depressive profile of memory impairment. For example, subclinical manifestations of depression cannot be proposed to be responsible for the nonspecific profile because the
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W. P. Horan et al.
depressed patients in this sample were diagnosed with a structured diagnostic interview and met full D S M - I I I - R criteria for Major Depressive Disorder. They scored in the moderate to severe range of depressive intensity on the BDI, suggesting that severity of depression in these adolescents was comparable to that in previous studies of memory impairments in depressed adults. Although significant differences in Verbal IQ were observed among the adolescent patient groups, the lack of group differences in memory functions were not attributable to the differences in verbal intelligence or differences in academic performance. Finally, no significant relationships were observed between CVLT variables and indices of severity of depression (BDI) or general psychiatric impairment (i.e., GAF ratings), suggesting that the level of impaired performance was not related to the severity of either depression or general maladjustment. The memory impairments of these adolescent patients are not due to the effects of an extensive history of substance abuse, medication, psychiatric hospitalization, or factors such as dementia, which are frequently encountered in adult depression research. Several explanations may be considered in the interpretation of these data. The nonspecific pattern of impairment seen, with essentially no findings specific to depression, could be due to a motivation related either to psychiatric symptoms or personality factors. However, the memory impairments found in depressed adults do not appear to be attributable to motivational effects (Richards & Ruff, 1989) and the normal performance of these adolescents on the Wechsler scales and on the WRAT-R would be difficult to reconcile with a general lack of motivation. It may be argued that CD and MDD share an underlying neuropathology that may account for the lack of diagnostic specificity. Indeed, CD has been conceptualized as an atypical manifestation of adolescent depression, as reflected by such notions as "masked depression" (Carlson & Cantwell, 1980). The fact that we carefully considered behavioral characteristics of all subjects and compared adolescents who had clear evidence of conduct disorder to those who did not reduces the likelihood that this explanation accounts for the performance profile seen. Depressed adolescent females were observed to perform substantially more poorly than norms for depressed adult females, although no substantial differences were observed among depressed males. The smallest difference that achieved statistical significance was .4 Z, while many of the differences were of a full standard deviation or more. These substantial relative deficits in female as compared to male patients with major depression may be attributable to differences in depression associated with adolescent onset in females. Adolescent females may have had more adverse life experiences associated with their current episode of depression than adult females with the same diagnosis. Additionally, since affective and psychotic disorders both tend to have a later age of onset in females than in males (Castle & Murray, 1993; Winokur, 1979), females with relatively early-onset depression may experience a more malignant form of the disorder with a very poor overall outcome and more significant cognitive impairment. These findings merit further study, including investigations of the relative base rates of adverse life experiences in male versus female adolescents with major depression. The current results may be attributed to characteristics of the CVLT. The CVLT is not specifically constructed to detect the specific patterns of performance characteristically found in depression. For example, it has been proposed that a pattern impairment on effortful versus automatic cognitive tasks (Hartlage et al., 1993) is specifically related to depression. The closest that any CVLT variables come to this conception is a comparison of recognition versus free recall performance. Several studies have reported recall versus recognition deficits on verbal learning tasks in depressed adults, although no such patterns of impaired CVLT performance were observed within the adolescent depressed group. Otto et al. (1994) also found that depressed outpatient adults performed more poorly than normative standards
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across each of the CVLT variables examined (although cued recall trials were not included). These results suggest that the CVLT may not capture specific patterns of impairment in depressed subjects. Some studies have found both recall and recognition impairments in depressed adults (Golinkoff & Sweeney, 1989; Wolfe et al., 1987), suggesting that inconsistencies among studies may be more closely related to variations in sample characteristics than the specific verbal learning task employed. It may also be the case that psychopathology in general is associated with poor performance on the CVLT. The majority of research concerning learning and memory impairments in depression have used normal comparison samples, while relatively few studies have included clinical comparison groups. Studies that have included clinical comparison samples have found less clear patterns of depression-specific impairment. For example, schizophrenic patients have been found to perform worse that depressed patients of tests of verbal learning and memory (Goldberg, Gold, Greenberg, Bigelow, & Weinberger, 1993), as have bipolar patients (Wolfe et al., 1987). Therefore, the substantial body of research reporting depressionspecific verbal learning and memory impairments may reflect a lack of comparison among clinical samples, rather than genuine depression-specific correlates. In fact, the classical definitions of information processing deficits in schizophrenia suggest that schizophrenia patients are also impaired on effortful, but not automatic processing tests (Callaway & Naghdi, 1982). Depressed adolescents demonstrate generalized memory impairments relative to normative standards on the CVLT. However, these impairments do not appear to be specific to depression among adolescent psychiatric disorders. Although the CVLT may not be an ideal measure for examining specific patterns of cognitive impairment in depression, the lack of diagnostic specificity observed in this study is unlikely to be attributable solely to the properties of this test. Impaired verbal learning and memory may be characteristic of adolescent psychopathology more generally, and reflect developmental differences from adult depression. However, the specificity of memory impairment that has been purported to accompany adult depression may reflect a relative lack of clinical comparison samples in previous research. Further research should attempt to examine the longitudinal characteristics of verbal learning and memory impairments found in adolescents diagnosed with depression or conduct disorder to more clearly delineate their relationship to adult psychopathology. The finding of nonspecific impairments in verbal memory in depression as compared to conduct disorders merits further investigation in order to determine if there are clues to the etiology of these illnesses associated with these findings. REFERENCES Beck, A. T., Ward, D. H., Mendelson, Mock, J., & Erbaugh, J. (1961). An inventory for measuring depression. Archives of General Psychiato,, 3, 561-571. Breslow, R., Kocsis, J., & Belkin, B. (1980). Memory deficits in depression: Evidence utilizing the Wechsler Memory Scale. Pereeptual and Motor Skills, 51, 541 542. Callaway, E., & Nagdhi S. (1982). An information processing model for schizophrenia. Archives o/ General Psyehiatry, 39, 339-347. Carlson, G. A., & Cantwell, M. D. (1980). Unmasking masked depression in children and adolescents. American Journal ~f Psychiato', 137, 445--449. Castle D. J., & Murray, R. M. (1993). The epidemiology of late-onset schizophrenia. Schizophrenia Bulletin, 19, 691-700. Cohen, R. M., Weingartner, H., Smallberg, S. A., Pickar, D., & Murphy. D. L. (1982). Effort and cognition in depression. Archives of General Psychiatry, 39, 593-597. Colby, C. A., & Gotlib, I. H. (1988). Memory deficits in depression. Cognitive Therapy and Research, 12, 611-627. Cronholm, B., & Ottoson, J. (1961). Memory functions in endogenous depression: Before and after electroconvulsive therapy. Archives of General Psychiatry, 5, 193-199.
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Delis, D. C., Kramer, J. H., Kaplan, E., & Ober, B. A. (1987). California Verbal Learning Test-Research edition, manual. New York: The Psychological Corporation. Goldberg, T. E., Gold, J. M., Greenberg, R., Bigelow, L., & Weinberger D. R. (1993). Contrasts between patients with affective disorders and patients with schizophrenia on a neuropsychological battery. American Journal of Psychiatry, 150, 1355-1362. Golinkoff, M., & Sweeney, J. A. (1989). Cognitive impairments in depression. Journal ~fAffective Disorders, 17, 105-112. Hartlage, S., Alloy, L. B., Vazquez, C., & Dykman, B. (1993). Automatic and effortful processing in depression. Psychological Bulletin, 113, 247-278. Henry, G. M., Weingartner, H., & Murphy, D. L. (1973). Influence of affective states and psychoactive drugs on verbal learning and memory. American Journal of Psychiatry, 130, 966-971. Jastrak, S. (1984). The wide-range achievement test-revised. Wilmington, DE: Jastrak Associates. Krames, L., & MacDonald, M. (1985). Distraction and depressive cognitions. Cognitive Therapy and Research, 9, 561-573. Otto, M. W., Bruder, G. E., Fava, M., Delis, D. C., Quitkin, E M., & Rosenbaum, J. F. (1994). Norms for depressed patients for the California Verbal Learning Test: Associations with depression severity and self-report of cognitive difficulties. Archives of Clinical Neuropsychology, 9, 81-88. Poznanski, E. (1982). The clinical phenomenology of childhood depression. American Journal of Orthopsyehiatry, 42, 308-313. Richards, P. M. & Ruff, R. M. (1989). Motivational effects on neuropsychological functioning: Comparison of depressed and nondepressed individuals. Journal of Consulting and Clinical Psychology, 57, 396-402. Roy-Byrne, P. P., Weingartner, H., Bierer, L. M., Thompson, K., & Post, R. M. (1986). Effortful and automatic cognitive processes in depression. Archives of General Psychiatry, 43, 265-267. Spitzer, R. L., Williams, J. B., Gibbon, M., & First, M. B. (1990). Struetured clinical interview .['or DSM-III-R (SCID). Washington, DC: American Psychiatric Press, Inc. Stromgren, L. S. (1977). The influence of depression on memory. Acta Psychiatrica Scandinavica, 56, 109-128. Weingartner, H. (1986). Automatic and effort demanding cognitive processes in depression. In L. W. Poon et al. (Eds.), Handbook for clinical memory assessment in older adults (pp. 218-225). Washington, DC: American Psychological Association. Weingartner, H., Cohen, R. M, Bunney, W. E., Ebert, M. H., & Kaye, W. (1982). Memory-learning impairments in progressive dementia and depression. American Journal of Ps.vchiatry, 139, 135-136. Weingartner, H., Burns, S. Diebel, R., & LeWitt, P. A. (1984). Cognitive impairments in Parkinson's disease: Distinguishing effort-demanding and automatic cognitive processes. Psychiatry Research, 11,223-235. Whitehead, A. (1974). Factors in the learning deficit of elderly depressives. British Journal (~fSocial and Clinical Psychology, 13, 201-208. Winokur, G. A. (1979). Unipolar depression. Archives of General Psychiatr),, 36, 47-52. Wolfe, J., Granholm, E., Butters, N., Saunders, E., & Janowsky, D. (1987). Verbal memory deficits associated with major affective disorders: A comparison of unipolar and bipolar patients. Journal of/tffective Disorders, 13, 83-92.
Archives of Clinical Neuropsychology,Vol. 12, No. 6, pp. 575 584, 1997 Copyright © 1997 National Academy of Neuropsychology Printed in the USA. All rights reserved 0887-6177/97 $17.00 + .00
PII S0887-6177(97)00012-7
Learning and Memory in Adolescent Psychiatric Inpatients with Major Depression: A Normative Study of the California Verbal Learning Test William P. Horan Four Winds Research Foundation
David L. Posse and Susan R. Borgaro Fairleigh Dickinson University and Four Winds Research Center
John M. Stokes Pace University
Philip O. Harvey Mt. Sinai School of Medicine
Depressed adults have deficits in memory functions, especially on demanding tasks, but few studies of depressed adolescents have been published. In order to examine the extent of memory impairment and its diagnostic specificit',; adolescent inpatients with DSM-III-R diagnoses of Major Depression (n = 56), Conduct Disorder (n = 42), or mixed Depression and Conduct Disorder (n = 22) were tested on the California Verbal Learning Test (CVLT) and compared to each other, to CVLT norms, and ta previously published CVLT norms for adults with Major Depression. Adolescents with Major Depression performed below normative standards on all aspects of the CVLT, but did not have a specific profile of memory impairments that was different f~'om the two comparison samples. Relative to norms for adult patients with Major Depression, adolescent females under performed across all CVLT measures, but males did not differ from adults Depression in adolescence is not associated with specific memory impairments, but adolescent females with depression may have more severe de/~cits than depressed adults. © 1997 National Academy of Neurop.~\vchology. Published by EIsevier Science Ltd
This research was supported by a grant from the National Institute of Drug Abuse to Dr. Posse. The authors would like to thank Drs. Joel Lord, Oscar Tanaka, and David Medoff for their assistance. William P. Horan is now at the University of New Mexico. Address correspondence to: Philip D. Harvey, Department of Psychiatry, Box 1229, Mt. Sinai School of Medicine, New York, NY 10029; E-mail: [email protected]. © 1997 National Academy of Neuropsychology. Published'by Elsevier Science Ltd
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Impairments in learning and memory have been extensively studied in depressed adults. A substantial body of literature has shown both quantitative and qualitative changes in the processing of verbal material in patients with depression. Various components of memory and learning have been implicated, including short-term memory (STM; Breslow, Kocsis, & Belkin, 1980; Colby & Gotlib, 1988; Richards & Ruff, 1989), long-term memory (LTM; Whitehead, 1974), and the transfer of information from STM to LTM (Henry, Weingartner, & Murphy, 1973; Krames & McDonald, 1985). In some studies the severity of depressive symptoms appears to be positively correlated with the degree of memory impairment found (Cohen, Weingartner, Smallberg, Pickar, & Murphy, 1982; Henry et al., 1973). Depressionrelated impairments are not simply attributable to a lack of motivation (Richards & Ruff, 1989) and have been shown to abate with remission of depressive symptoms in response to somatic and psychotherapeutic interventions (e.g., Cronholm & Ottoson, 1961; Stromgren, 1977), suggesting that these cognitive impairments are state-dependent features of depression. Performance deficits found in depressed adults have typically been on tasks using neutrally valenced material and requiring effortful cognitive processing (e.g, immediate recall, delayed recall, list learning). In fact, considerable evidence supports the hypothesis that depression interferes with tasks requiring effortful processing, but only minimally interferes with automatic processing tasks (e.g., frequency encoding, spatial location encoding: Hartlage, Alloy, Vazquez, & Dykman, 1993; Weingartner, 1986; Weingartner, Cohen, Bunney, Ebert, & Kaye, 1982; Weingartner, Burns, Diebel, & LeWitt, 1984). Deficiencies in effort-demanding processing strategies have been found in depressed patients, including poor use of encoding strategies (Cohen, 1982; Roy-Byrne, Weingartner, Bierer, Thompson, & Post, 1986), reduced levels of organization at encoding (Cohen et al., 1982; Weingartner, 1986), and reductions in recall memory (Colby & Gotlib, 1988; Krames & McDonald, 1985). In fact, Hartlage et al. (1993) proposed that this pattern of cognitive impairment may be specific to depression, as compared to other psychiatric disorders. The frequency with which these impairments have been found has led researchers to call for norms to understand the performance of depressed individuals. Otto et al. (1994) recently published normative data for depressed adults on the California Verbal Learning Test (CVLT), a widely used clinical measure of verbal learning and memory. They found that depressed outpatients performed between one half to one standard deviation below normative standards from the CVLT manual. These impairments affected men and women equally, were apparent after controlling for the effects of education, and were not associated with the severity of depression. Despite substantial evidence that depressive disorders in adolescence are phenomenologically similar to depressive disorders in adults (e.g., Poznanski, 1982), the characteristics of memory functioning in major depression and the correlations between severity of depression and level of memory impairment in adolescence remains unclear. No studies investigating the performance of adolescent patients with major depression have yet been published. In this study, verbal learning and memory were studied with the CVLT in adolescent inpatients diagnosed with Major Depressive Disorder, as well as comparison groups with Conduct Disorder and the dual diagnosis of Major Depression and Conduct Disorder. It was predicted that depressed adolescents, like adults with Major Depression, would perform poorly relative to normative standards for the CVLT. There were no specific predictions regarding the performance of adolescent patients with Conduct Disorder or the interaction of Conduct Disorder and Major Depression. If deficits in certain components of memory functioning were specific to depression it would be expected that patients with Major Depression would underperform relative to comparison subjects without depression. This study also sought to compare the level of impairment found in depressed adolescents to that previously seen in
Memo O, in Adolescent Depression
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depressed adults in the Otto et al. (1994) study. Thus, the study examines memory functioning in adolescent Major Depression, both in terms of diagnostic specificity and severity compared to adult norms for normal and depressed individuals.
METHODS Participants Participants in this study were consecutive admissions to adolescent inpatient units of a private psychiatric hospital. All were recruited within 1 week of admission and their assent to participate was solicited, followed by parental informed consent. They were interviewed with the Structured Clinical Interview for DSM-111-R (SCID; Spitzer, Williams, Gibbon, & First, 1990) by a trained interviewer and a comprehensive chart review was performed. This comprehensive chart review included the use of the specific DSM-III-R criteria for Conduct Disorder in checklist form, since the SCID does not have specific modules for this diagnosis. DSM-III-R diagnoses were generated by the interviewer and cross-checked by one of the authors (PDH). In order to document the reliability of the diagnostic process, two raters performed 50 diagnostic interviews and chart reviews simultaneously. One rater performed the interview and both raters generated diagnostic ratings. Of the total of 73 psychiatric diagnoses obtained with this procedure, the raters disagreed on 4, resulting in a Kappa coefficient of .89 (p < .001). Raters also generated a Global Assessment of Functioning (GAF) score on the basis of the information collected in the assessment. This score ranges from I to 100 and measures global adjustment, including psychiatric symptoms and adaptive functions. Lower scores indicate poorer functioning. The interrater reliability (lntraClass correlation) was .98 for the 50 overlapping GAF scores. Depressed subjects were included in the present study only if they received a DSM-111-R diagnosis of Major Depressive Disorder. Subjects meeting criteria for other depressive disorders (Dysthymic Disorder, Depression NOS) were excluded, in order to increase the homogeneity of subjects within the depressed group. Since a goal of this research was to examine the specificity of verbal learning and memory impairments to depression, comparison groups of adolescents diagnosed with Conduct Disorder or both Major Depressive Disorder and Conduct Disorder were also studied. No subjects had a Bipolar Disorder diagnosis. While five of the Major Depression patients had a secondary diagnosis of an anxiety disorder, none of the patients in the other two groups had a secondary diagnosis in the anxiety disorder domain. Six depressed patients had an eating disorder diagnosis and two patients in the Conduct Disorder group and none of the mixed group had an eating disorder diagnosis. The prevalence of substance abuse disorder diagnoses was considerably higher and is presented, along with other descriptive information, in Table 1. Substance abuse as rated in this study included abuse of or dependence on either alcohol or cannabis, as determined by the SCID interview. All subjects with a Wechsler Full-Scale IQ score of less than 80 were excluded, as were all subjects who were uncooperative with testing on any of the cognitive measures. Further exclusion criteria included any subject with an acquired or developmental neurological disorder, including developmental learning disorders, seizure disorders, or history of disease or trauma involving the brain. Materials and Design California Verbal Learning Test (CVLT). The CVLT (Delis, Kramer, Kaplan, & Ober, 1987) consists of five serial verbal presentations of a 16-item word list (List A: "Monday's
578
W. P. Horan et al. TABLE 1 Demographic Data on All Subjects
Depressed N Age % Male BDI scorea Verbal IQ WRAT-R reading subtest % Substance abuse Global assessment of functioning (GAF)b
56 15.13 (I.61) 31% 21.26(11.07) 104.46(14.07) 104.89(13.85) 16% 51.38(10.32)
Diagnostic Group Conduct Disordered 42 15.28 (1.20) 64% 9.55 (8.38) 98.93(11.97) 103.96(14.09) 54% 50.80(14.26)
Mixed 22 14.86 (1.32) 45% 15.15 (9.61) 96.23 (9.01) 101.78(14.82) 30% 51.08 (7.08)
Note. Standard deviations are in parentheses. aHigher scores reflect more severe impairment. bLower scores reflect poorer functioning.
shopping list") composed of items semantically related to four common categories. Following each presentation, testees are asked to recall as many items as they can in any order. After the fifth learning trial, a second list (List B: "Tuesday's shopping list"), also consisting of four items from each of four semantic categories, is presented once. After recalling List B, the testee is asked to recall List A (Short Delay), first without (Free Recall) and then with semantic cues. Then there is a delay period of 20 minutes. After the delay, the testee is again asked to recall items from List A, first without and then with semantic cues, after which a recognition trial is administered. There are multiple dependent variables derived from the CVLT. In the current study, the variables examined are trial 1 recall, total learning over trials 1 to 5, list A, trial 5 recall, list B recall, and long and short delayed free and cued recall.
Beck Depression Inventory. All patients completed the Beck Depression Inventory-long form (BDI; Beck, Ward, Mendelson, Mock, & Erbaugh, 1961). The BDI contains 21 items on which the patient provides self-reports in response to statements regarding the severity of depression on a 4-point (0-3) scale. The dependent variable used was the total score. Wide-Range Achievement Test-Revised (WRAT-R) word recognition subtest. As a portion of their psychological evaluation at the hospital, all participants were examined with the Wide-Range Achievement Test-Revised (WRAT-R; Jastrak, 1984). This subtest requires participants to read a list of words of ascending difficulty, with one point given for each correct pronunciation of the words. Scores can be converted either to grade or "standardized" IQ-equivalent scores. In order for these scores to be compared to the participants' obtained verbal IQs to examine academic under performance relative to estimated intelligence, the IQ-equivalent scores were calculated and used as the dependent variable.
Procedure Participants were assessed with the SCID within 2 days of their recruitment into the project, which occurred within 7 days of their admission to the hospital. After SCID assessment, they were given the research testing battery, including the CVLT, in a single testing session. Since all adolescent patients in the setting where this research was conducted undergo comprehensive psychological testing for purposes of clinical assessment, the verbal IQ, reading, and BDI data were extracted from their clinical chart.
Memory in Adolescent Depression
579
Data Analysis Since the normative data for the CVLT were established in neurologically intact individuals aged 17 to 34 years, the applicability of the normative data to the present sample (M age 15.2) was examined statistically. The performance of participants who were over 17, and hence "old enough" to be administered the CVLT was compared to younger ones. A 3 (diagnostic group) x 2 (age 17 vs. less than 17) MANCOVA, with Verbal IQ as the covariate, was performed on the CVLT variables examined in this study. Results of this analysis revealed no main effects for age, F(2, 113) = .830, p > .05, and no group x age interaction effect, F(2, 113) = 1.08, p > .05. Therefore, no statistically significant differences were obtained on the CVLT scores between participants aged 17 (n = 22), and those aged less than 17 years (n = 98), suggesting that the task is not too difficult for the younger participants. To allow for comparison between patient groups and normative data, raw scores were transformed to standard scores according to the norms provided in the CVLT manual. All scores are z-scores other than the Total Recall, trials 1 to 5 score, which is a T-score.
RESULTS The patient samples were compared on their Verbal IQ scores, WRAT-R word recognition scores, and BDI total scores with analysis of variance (ANOVA). There was a significant group difference in VIQ, F(2, 118) = 4.10, p < .05. Tukey post hoc tests found only one significant group difference: that the patients with major depression had significantly higher scores than patients with a diagnosis of both conduct disorder and major depression. There was also a significant overall difference in BDI scores, F(2, 118) = 7.02, p < .001. Tukey post hoc tests revealed that the only significant group difference was a significantly higher score in the major depression patients compared to the conduct disorder group. There were no group differences in WRAT-R reading scores, however, F(2, 118) = 1.46, p > .05. The gender distributions of the samples were compared with chi-square tests, finding a significant overall difference ×2(2) = 12.08, p < .005. There were more females in the two groups with depression and more males in the pure Conduct Disorder group. Performance on all of the CVLT variables for the three groups is presented in Table 2. T-tests were computed to compare substance abusers and nonabusers on each of the CVLT scores. None of these analyses found a significant difference [all t(l18) < 1.45, all p > .15]. Additional t-tests were computed to compare medicated versus nonmedicated patients on each of the CVLT scores. None of these analyses found a significant difference [all t(118) < 1.18, all p > .24]. The first principal analysis of CVLT performance was a 2 (Gender) x 3 (Diagnosis) Multivariate analysis of variance (MANOVA) for all of the CVLT variables. These analyses were performed on the T or standard scores. There was no overall difference between the diagnostic groups, Wilks Lambda = .88, Pillais Approx. F(18, 208) = .74, p = .77 and none of the univariate effects were significant either. There were no significant Gender effects, Wilks lambda -- .91, Pillais Approx. F(9, 103) -- 1.14, p = .34, with no univariate effects significant either. Finally, the Gender x Diagnosis interaction was also nonsignificant, Wilks lambda -- .89, Pillais Approx F(18, 208) -- .68, p -- .83. No Univariate interactions were significant. As a result, the data presented in Table 2 are not broken down by gender. Since the groups differed significantly in VIQ, the MANOVA was repeated with a multivariate analysis of covariance (MANCOVA), with VIQ as the covariate. Significant [all t(l18) > 4.91, all p < .001] covariate effects were found for all CVLT variables other than recognition hits, t(118) = .90, p = .37. However, none of the multivariate diagnostic group or gender main
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W. P Horan et al.
TABLE 2 Group Means Across CVLT Variables
Depressed
Total Recall 1-5 List A, Trial 1 List A, Trial 5 List B Recall SD Free Recall SD Cued Recall LD Free Recall LD Cued Recall Recognition Hits
Diagnostic Group Conduct Disordered
Mixed
Raw
Standard
Raw
Standard
Raw
Standard
52.59 (8.62) 7.09 (2.08) 12.17 (1.99) 6.50 (1.68) 11.41 (2.29) 11.56 (2.33) 11.02 (2.58) 11.63 (2.52) 14.63 (1.23)
33.93 (13.81) - 1.17 (1.24) -2.46 (1.60) -.87 (.83) - 1.33 (1.29) - 1.80 (1.29) -2.02 (1.47) -2.02 (1.47) - 1.67 (1.59)
51.90 (8.85) 7.12 (1.98) 12.00 (2.43) 6.43 (1.74) 10.69 (2.53) 11.45 (2.56) 10.95 (2.65) 11.50 (2.44) 14.52 ( 1.58)
36.05 (14.22) -.98 (I.07) -2.14 (I .90) -.67 (.95) - 1.40 (1.45) - 1.55 ( 1.60) -1.60 ( 1.50) - 1.79 (1.51) - 1.64 (1.76)
53.57 (8.89) 7.33 (2.22) 12.52 (2.09) 6.14 (2.63) 10.67 (2.15) 10.73 (4.80) 10.32 (4.90) 10.68 (4.90) 13.59 (5.23)
36.81 (15.09) - 1.0 (1.26) -2.05 (1.94) -.95 (1.40) - 1.57 (1.29) - 1.57 (1.17) -1.86 (1.46) - 1.81 ( 1.54) - 1.52 ( 1.69)
Note. Only the Total Recall, trials 1-5 is a t-score, all other standard scores are z-scores; standard deviations are
presented in parentheses. SD = Short Delay; LD = Long Delay.
effects or t w o - w a y interactions w e r e altered by the use o f V I Q as a covariate. In the next analysis, Pearson correlations w e r e c o m p u t e d b e t w e e n each of the C V L T variables and B D I total scores and G A F scores. N o n e o f the correlations w e r e significant (all r < .20, all p > .O6). The p e r f o r m a n c e of the depressed adolescents was c o m p a r e d to the n o r m a t i v e standards of the C V L T Research manual, with these c o m p a r i s o n s p e r f o r m e d separately with t-tests for males and females. Patients consistently u n d e r p e r f o r m e d on all variables, with all scores for all groups on all variables, other than list B recall, found to be 1 or m o r e S D b e l o w n o r m a t i v e standards. The only nonsignificant c o m p a r i s o n was for list B recall for the male patients with m i x e d depression and conduct disorders, t(8) = 1.67, p < . 10. All other t values w e r e > 2 . 1 2 , all p < .05. In the final analysis, the C V L T p e r f o r m a n c e of the depressed adolescents was c o m p a r e d to the p r e v i o u s study o f depressed adults. T h e s e analyses were p e r f o r m e d separately by gender, because o f the gender-specific C V L T norms, and the analyses e x c l u d e d the cuedrecall variables, w h i c h w e r e not collected in the Otto et al. (1994) n o r m a t i v e study o f adult patients. T-tests w e r e used to c o m p a r e the p e r f o r m a n c e o f the current sample o f adolescents with m a j o r depression to the p r e v i o u s l y published adult norms. As presented in Table 3, the f e m a l e adolescent patients p e r f o r m e d m o r e poorly than the f e m a l e adult patients on each o f the C V L T variables. In the m a l e subjects, significant differences were found only for List A, trial 5 p e r f o r m a n c e and long-delay free recall, with adolescent patients p e r f o r m i n g m o r e poorly.
Memo~' in Adolescent Depression
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TABLE 3
Comparison of Depressed Adolescent Patients and the Norms for Depressed Adults Depressed Females
Depressed Males
Total Recall, Trials 1 5 List A, Trial 1 List A, Trial 5 List B Recall Short-Delay Free Recall Long-Delay Free Recall Long-Delay Recognition
Adolescents
Adults
t-Values
Adolescents
Adults
t-Values
37.31 (16.29) -.81 (1.38) -2.38 (1.75) -.69 (.79) - 1.13 ( 1.71 ) 1.75 (1.44) 1.50 ( 1.55)
42.20 (15.21) .87 (.98) -.89 (2.04) -.23 (I.15i -.47 (1.30) -.75 ( 1.38l -.92 ( 1.75 )
1.19
32.50 (12.59) -1.32 (1.16) 2.50 (1.55) -.95 (.84) - 1.92 ( 1.08) -2.13 (1.40) - 1.74 (1.62)
41.6 (13.21 -.77 (1.14) -1.12 (1.64) -.52 (1.14) -.62 ( 1.53 ) -.92 ( 1.51 ) -.59 (1.42)
3.49***
19 2.66** 1.48 1.69 2.56* 1.21
2.39** 4.31"** 2.05* 4.64*** 4.64*** 3.83***
Note. Only the Total Recall, Trials 1-5 is a t-score, all other standard scores are :-scores; z-scores are in parentheses, *p "< .05; **p < .01; ***p < .001.
DISCUSSION Depressed adolescent patients were found to perform significantly more poorly than normative data for the CVLT. However, these impairments were not observed to be specifically related to depression. Rather, a general verbal learning and memory impairment was observed across the different groups of adolescent inpatients. The magnitude of impairment of these patients was substantial, with patients in all groups performing -<1 SD below normative standards on average across all variables other than list B learning. Male adolescent inpatients performed as poorly as normative standards for adults with major depression, while female adolescent inpatients performed more poorly than the depressed female patients in the previous normative sample. Methodological limitations in the current study should be considered before interpreting these results. The lack of a comparison sample of normal adolescents limits the extent to which conclusions may be drawn concerning the verbal learning and memory abilities of the adolescents examined in this study. Adolescent norms for the CVLT are currently lacking and would be useful. Analyses revealed no significant differences between adolescents aged 17 years and less than 17 on any of the CVLT variables examined, suggesting that the impairments observed are not simply attributable to this test being overly challenging for this younger population. Additional limitations include the fact that a proportion of the subjects in this sample were medicated or had a recent history of substance abuse. However, no differences were observed between substance abusing versus non-abusing, or medicated versus nonmedicated patients, suggesting that these/'actors did not significantly influence the results of cognitive testing in this study. A final limitation is the small sample size of the mixed conduct disorder and depression group. Since this group is so small, interpretations regarding characteristics of the overlap between conduct disorder and depression should not be drawn from this study. Several of the factors that have been proposed to mediate the relationship between depression and memory performance also did not appear to account for the lack of a specific depressive profile of memory impairment. For example, subclinical manifestations of depression cannot be proposed to be responsible for the nonspecific profile because the
582
W. P. Horan et al.
depressed patients in this sample were diagnosed with a structured diagnostic interview and met full D S M - I I I - R criteria for Major Depressive Disorder. They scored in the moderate to severe range of depressive intensity on the BDI, suggesting that severity of depression in these adolescents was comparable to that in previous studies of memory impairments in depressed adults. Although significant differences in Verbal IQ were observed among the adolescent patient groups, the lack of group differences in memory functions were not attributable to the differences in verbal intelligence or differences in academic performance. Finally, no significant relationships were observed between CVLT variables and indices of severity of depression (BDI) or general psychiatric impairment (i.e., GAF ratings), suggesting that the level of impaired performance was not related to the severity of either depression or general maladjustment. The memory impairments of these adolescent patients are not due to the effects of an extensive history of substance abuse, medication, psychiatric hospitalization, or factors such as dementia, which are frequently encountered in adult depression research. Several explanations may be considered in the interpretation of these data. The nonspecific pattern of impairment seen, with essentially no findings specific to depression, could be due to a motivation related either to psychiatric symptoms or personality factors. However, the memory impairments found in depressed adults do not appear to be attributable to motivational effects (Richards & Ruff, 1989) and the normal performance of these adolescents on the Wechsler scales and on the WRAT-R would be difficult to reconcile with a general lack of motivation. It may be argued that CD and MDD share an underlying neuropathology that may account for the lack of diagnostic specificity. Indeed, CD has been conceptualized as an atypical manifestation of adolescent depression, as reflected by such notions as "masked depression" (Carlson & Cantwell, 1980). The fact that we carefully considered behavioral characteristics of all subjects and compared adolescents who had clear evidence of conduct disorder to those who did not reduces the likelihood that this explanation accounts for the performance profile seen. Depressed adolescent females were observed to perform substantially more poorly than norms for depressed adult females, although no substantial differences were observed among depressed males. The smallest difference that achieved statistical significance was .4 Z, while many of the differences were of a full standard deviation or more. These substantial relative deficits in female as compared to male patients with major depression may be attributable to differences in depression associated with adolescent onset in females. Adolescent females may have had more adverse life experiences associated with their current episode of depression than adult females with the same diagnosis. Additionally, since affective and psychotic disorders both tend to have a later age of onset in females than in males (Castle & Murray, 1993; Winokur, 1979), females with relatively early-onset depression may experience a more malignant form of the disorder with a very poor overall outcome and more significant cognitive impairment. These findings merit further study, including investigations of the relative base rates of adverse life experiences in male versus female adolescents with major depression. The current results may be attributed to characteristics of the CVLT. The CVLT is not specifically constructed to detect the specific patterns of performance characteristically found in depression. For example, it has been proposed that a pattern impairment on effortful versus automatic cognitive tasks (Hartlage et al., 1993) is specifically related to depression. The closest that any CVLT variables come to this conception is a comparison of recognition versus free recall performance. Several studies have reported recall versus recognition deficits on verbal learning tasks in depressed adults, although no such patterns of impaired CVLT performance were observed within the adolescent depressed group. Otto et al. (1994) also found that depressed outpatient adults performed more poorly than normative standards
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across each of the CVLT variables examined (although cued recall trials were not included). These results suggest that the CVLT may not capture specific patterns of impairment in depressed subjects. Some studies have found both recall and recognition impairments in depressed adults (Golinkoff & Sweeney, 1989; Wolfe et al., 1987), suggesting that inconsistencies among studies may be more closely related to variations in sample characteristics than the specific verbal learning task employed. It may also be the case that psychopathology in general is associated with poor performance on the CVLT. The majority of research concerning learning and memory impairments in depression have used normal comparison samples, while relatively few studies have included clinical comparison groups. Studies that have included clinical comparison samples have found less clear patterns of depression-specific impairment. For example, schizophrenic patients have been found to perform worse that depressed patients of tests of verbal learning and memory (Goldberg, Gold, Greenberg, Bigelow, & Weinberger, 1993), as have bipolar patients (Wolfe et al., 1987). Therefore, the substantial body of research reporting depressionspecific verbal learning and memory impairments may reflect a lack of comparison among clinical samples, rather than genuine depression-specific correlates. In fact, the classical definitions of information processing deficits in schizophrenia suggest that schizophrenia patients are also impaired on effortful, but not automatic processing tests (Callaway & Naghdi, 1982). Depressed adolescents demonstrate generalized memory impairments relative to normative standards on the CVLT. However, these impairments do not appear to be specific to depression among adolescent psychiatric disorders. Although the CVLT may not be an ideal measure for examining specific patterns of cognitive impairment in depression, the lack of diagnostic specificity observed in this study is unlikely to be attributable solely to the properties of this test. Impaired verbal learning and memory may be characteristic of adolescent psychopathology more generally, and reflect developmental differences from adult depression. However, the specificity of memory impairment that has been purported to accompany adult depression may reflect a relative lack of clinical comparison samples in previous research. Further research should attempt to examine the longitudinal characteristics of verbal learning and memory impairments found in adolescents diagnosed with depression or conduct disorder to more clearly delineate their relationship to adult psychopathology. The finding of nonspecific impairments in verbal memory in depression as compared to conduct disorders merits further investigation in order to determine if there are clues to the etiology of these illnesses associated with these findings. REFERENCES Beck, A. T., Ward, D. H., Mendelson, Mock, J., & Erbaugh, J. (1961). An inventory for measuring depression. Archives of General Psychiato,, 3, 561-571. Breslow, R., Kocsis, J., & Belkin, B. (1980). Memory deficits in depression: Evidence utilizing the Wechsler Memory Scale. Pereeptual and Motor Skills, 51, 541 542. Callaway, E., & Nagdhi S. (1982). An information processing model for schizophrenia. Archives o/ General Psyehiatry, 39, 339-347. Carlson, G. A., & Cantwell, M. D. (1980). Unmasking masked depression in children and adolescents. American Journal ~f Psychiato', 137, 445--449. Castle D. J., & Murray, R. M. (1993). The epidemiology of late-onset schizophrenia. Schizophrenia Bulletin, 19, 691-700. Cohen, R. M., Weingartner, H., Smallberg, S. A., Pickar, D., & Murphy. D. L. (1982). Effort and cognition in depression. Archives of General Psychiatry, 39, 593-597. Colby, C. A., & Gotlib, I. H. (1988). Memory deficits in depression. Cognitive Therapy and Research, 12, 611-627. Cronholm, B., & Ottoson, J. (1961). Memory functions in endogenous depression: Before and after electroconvulsive therapy. Archives of General Psychiatry, 5, 193-199.
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