A comparison of the Diagnostic Assessment for the Severely Handicapped-II (DASH-II) and the Aberrant Behavior Checklist (ABC)

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Research in Developmental Disabilities, Vol. 18, No. 4, pp. 289-298, 1997 Copyright © 1997 Elsevier Science Ltd Printed in the USA. All rights reserved 0891-4222/97 $17.00 + .00

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A Comparison of the Diagnostic

Assessment for the Severely Handicapped-II (DASH-II) and the Aberrant Behavior Checklist (ABC) Theodosia R. Paclawskyj, Johnny L. Matson, Jerald W. Bamburg, and Christopher S. Baglio Louisiana State University

It is generally accepted that persons with mental retardation are subject to higher rates of psychopathology than individuals of normal intelligence (Matson & Barrett, 1993; Rojahn & Tasse, 1996). Yet, the limitations experienced by individuals with mental retardation often preclude traditional diagnostic evaluations. For example, individuals with mental retardation may (a) not be able to adequately communicate their experiences, (b) display deficits in social skills that are mistaken for psychopathology, (c) show stress-induced bizarre behaviors, and (d) exhibit increased severity of maladaptive behavior and cognitive delay (Sovner, 1986). Therefore, while there is considerable evidence of the high prevalence of psychopathology in the mentally retarded population, precise estimates are limited by difficulties in assessing this population. Evaluating the severely and profoundly mentally retarded population poses a particular challenge to the clinician in that the limitations described by Sovner (1986) are greater. When clients have few or no communication skills, examiners may tend to attribute abnormalities in behavior to low cognitive functioning rather than to a mental disorder (Borthwick-Duffy & Eyman, 1990). In contrast, there are lesser communication barriers with the mildly and moderately retarded population. Consequently, mildly and moderately retarded individuals tend to receive more psychiatric diagnoses than persons with severe and profound mental retardation. However, the higher reported rate of maladaptive 289

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T. R. Paclawskyj, J. L. Matson, J. W. Bamburg, and C. S. Baglio

behaviors in the latter group instead may indicate undiagnosed psychiatric problems (Borthwick-Duffy & Eyman, 1990). Researchers have substantiated the application of a DSM-based nosology to behavioral disturbances in people with mental retardation (Borthwick-Duffy, 1994; Matson & Barrett, 1993). Professionals are concerned, however, as to the extent of generalization of the DSM system to the severely and profoundly retarded population (Einfield & Aman, 1995; Rojahn & Tasse, 1996). That is, are traditional diagnostic categories still appropriate or do the behavioral disorders prevalent in mental retardation represent unique psychiatric disorders? Borthwick-Duffy (1994) noted that if the interrelationship between assessment instruments and DSM categories is not clarified, future epidemiological studies will be biased for the type of instrument used. Efforts are needed to validate a system of classification and method of assessment that will better serve this population (Einfield & Aman, 1995). Similarly, establishing accurate clinical diagnosis is essential to ensuring appropriate treatment, both psychological and pharmacological (Sturmey, 1995b). Given high psychotropic usage with the mentally retarded population, valid diagnosis is critical (Sturmey, 1995a). Regarding the relationship between established psychiatric disorders and severe behavior disorders, Rojahn, Borthwick-Duffy, and Jacobson (1993) found no linear correlation between four major behavior problems (aggression, self-injurious behavior, destruction, or stereotypies) and psychiatric diagnoses. However, Borthwick-Duffy and Eyman (1990), in a discriminant analysis, identified the following eight behaviors that predicted dual diagnosis: (a) depression, (b) aggression, (c) self-injury, (d) resistive behaviors, (e) tantrums, (f) running away/wandering, (g) adjustment to social change, and (h) socially inappropriate behavior. Sturmey (1995a) noted that behavior disorders are sufficiently heterogeneous to preclude assigning individual problem behaviors to particular psychiatric disorders. Maladaptive behaviors may be learned, associated with physical illness or distress, a consequence of organic problems, or appropriate for the individual's developmental level. In short, the interrelationship between problem behaviors and psychiatric diagnoses clearly is complex and requires further clarification. Presently there are two assessment measures applicable to persons with severe and profound mental retardation: the Diagnostic Assessment for the Severely Handicapped (DASH-I1) (Matson, Gardner, Coe, & Sovner, 1991) and the Aberrant Behavior Checklist (ABC) (Aman & Singh, 1986). The DASH-H was derived from the DSM classification system and past studies of dual diagnosis. There are 13 subscales for screening purposes: (1) Anxiety, (2) Depression, (3) Mania, (4) PDD/Autism, (5) Schizophrenia, (6) Stereotypies, (7) Self-injury, (8) Elimination, (9) Eating, (10) Sleep, (11) Sexual, (12) Organic, and (13) Impulse. Psychometric studies with the DASH-H have included measures of internal and external reliability (Matson, Gardner, et al., 1991; Sevin, Matson, Williams, & Kirkpatrick-Sanchez, 1995) and factor analysis (Matson,

DASH-H and ABC

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Coe, Gardner, & Sovner, 1991). Inter-rater and test-retest reliability were adequate for the frequency and duration dimensions but low for severity. Internal consistency was moderate, indicating that the subscales may reflect more heterogeneous clusters of behaviors. Factor analysis yielded a six-factor structure: (1) Emotional Lability, (2) Aggression/Conduct Disorder, (3) Language Disorder/Verbal Aggression, (4) Social Withdrawal/Stereotypy, (5) Eating Disorder, and (6) Sleep Disorder. These factors correspond to the general trend of behavior categories emerging in the dual diagnosis literature (Einfield & Aman, 1995). The ABC is an empirically-derived measure initially developed to assess pharmacological, behavioral, and other treatment effects on the behavior of mentally retarded children and adults (Aman & Singh, 1986). A factor analysis of items yielded five subscales: (1) Irritability, Agitation, Crying, (2) Lethargy, Social Withdrawal, (3) Stereotypic Behavior, (4) Hyperactivity, Noncompliance, and (5) Inappropriate Speech. These factors correspond well to the categories of disorders established in the literature (Einfield & Aman, 1995). The ABC also has well-established reliability and validity in a residential setting (Aman, 1991; Aman & Singh, 1986). Within the literature on dual diagnosis assessment instruments, Sturmey and Bertman (1994) conducted a validity study of the Reiss Screen for Maladaptive Behavior (Reiss, 1988) by correlating scores on the Reiss Screen with those of the Psychopathology Instrument for the Mentally Retarded (Matson, 1988) and the ABC. While their sample included a significant portion of individuals with severe and profound mental retardation, no study to date has compared the only two instruments for this group: the DASH-H and the ABC. Therefore, the current study examines the validity of the DASH-H through correlation with the ABC. As this is a comparison of an empirically-derived measure to a taxonomy-based measure, the resulting subscale comparisons are also discussed in terms of classification of psychopathology in persons with severe and profound mental retardation. METHOD Participants

Participants were 233 severely and profoundly mentally retarded residents of a large developmental center in Louisiana. Diagnoses of mental retardation were made with individually administered standardized intelligence tests and adaptive behavior scales. Participants ranged in age from 4 to 86 years old and were predominantly Caucasian (75.1%) (see Table 1 for additional demographic information). Assessment

The DASH-H and ABC were administered by Master' s level therapists to direct care staff who had known the participants for at least 6 months. The examiners

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Table 1 Demographic Characteristics

Variable Gender Male Female Race Caucasian African American Other Age 0-10 11-20

21-30 31--40 41-50 51-60 61-70 71 years and up Level of Mental Retardation Mild Moderate Severe Profound Unknown

Percent 55.4 44.6 75.1 24.0 0.9 1.3 8.1

9.9 27.5 24.0 11.6 9.9 7.7 2.2 5.2 15.1 75.4 2.1

attended training seminars on the DASH-H and A B C and were supervised by licensed psychologists. The assessments took place on each participant's home, with the examiner and rater sitting in a relatively quiet setting. Items from the assessments were clarified by the examiners by request and when inconsistent information was provided. The administration time for the two instruments was approximately 45 minutes.

Analyses First, to evaluate overall convergent validity between the DASH-H and the ABC, Pearson correlation coefficients were calculated between the subscales of each measure. Next, to determine if instrument-specific psychometrics affected this comparison, coefficient alpha values were computed for each subscale o f both tests. Because of the relatively large number of tests performed, the significance level was set at .001 for all comparisons. In the third set of analyses, DASH-H factor scores were computed according to the factor structure identified by (Matson, Coe, Gardner, & Sovner, 1991). These scores were then compared to the A B C subscale scores through Pearson correlation coefficients to determine if the similarities in content described by

DASH-H and ABC

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Table 2 Correlation Coefficients for DASH-H and ABC Subscales

ABC Subscales DASH-II Subscale Irritability Lethargy Stereotypies Hyperactivity Speech Anxiety Depression Mania PDD/Autism Schizophrenia Stereotypies Self-injury Elimination Eating Sleep Sexual Organic Impulse Total

.3266* .5594* .6335* .2408* .2096 .1599 .4829* - .0997 .1888 .3189" .4061" .5121" .7620* .7282*

.1218 .3848* .1393 .3626* .2263* .1932 .2387* - .0660 .2368* .2385* .1694 .3148" .0799 .3228*

.(1716 .2670* .1758 .6511* .2022 .6729* .3601* .(1559 .1949 .1273 .1521 .2163" .(1229 .3715"

.3117" .5341* .6798* .3757* .2593" .2253* .3791* - . 1375 .2576* .3408* .4587* .5875* .6917" .7255*

.0677 .3432* .3147" .1544 .1760 .1389 .0056 - .0681 .0017 .2949* .0658 .2097 .1690 .2590*

Total .3127" .6344* .5992* .5102" .3081* .3567* .4692* - . 1183 .2931* .3876* .4178" .5934* .5784* .7521"

*p < .001.

Einfield and Aman (1995) could be empirically validated. Results are discussed in terms of implications for dual diagnosis classification.

RESULTS

A relatively high degree of overall concurrent validity of the DASH-H, which demonstrated through a significant correlation between the total DASH-II and ABC scores (.7521, p < .001) (see Table 2). Of the DASH-II subscales the Depression, Mania, Organic Disorders, and Impulse Control Disorders/Miscellaneous subscales all correlated very highly (above r = .5000) with the Irritability and Hyperactivity subscales from the ABC. The highest correlation was between the Impulse ControlfMiscellaneous and Irritability subscales (r = .7620). Of these DASH-II subscales, all four also were highly intercorrelated (see Table 3), as were the two ABC subscales (see Table 4). In addition, both the PDD/Autism and Stereotypies subscales of the DASH-H correlated strongly with the Stereotypies subscale of the ABC (above .6500). Again, these two DASH-II subscales showed very high correlation with each other (r = .8540, p < .001). Internal consistencies of both the DASH-H and ABC were acceptable (see Table 5). For the DASH-H, average Cronbach alpha for the subscales was .5141, with a range from a low of .2843 (Sleep Disorders) to a high of .8418 (Impulse Control Disorder/Miscellaneous). The four DASH-II subscales with strong correlations all had adequate alpha values ranging from .5307 to .8418. The mean alpha value for the ABC subscales was even higher at .8840 [ranging from .7872

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Table 3 Correlation Coefficients for D A S H . H Subscales Anxiety Depression Mania PDD/Autism Schizophrenia Stereotypies Depression Mania PDD/Autism Schizoph~nia Stereotypies SIB Elimination Eating Sleep Sexual Organic Impulse

Eating Sleep Sexual Organic Impulse

.3395* .2772* .1847 .0724 .0973 .1613 .0001 .0054 .1702 .0483 .2761" .3356* Elimination .0358 .1100 .1314 .0316 -.1019

.7094* .4601" .3052* .2859* .3049* .0540 .3175" .5114" .2941" .7653* .5218"

.3702* .2966* .2294* .2714" -.0331 .2073 .3116" .2428* .7915" .6426*

.2640* .8540* .3158" .0679 .2962* .2064 .2854* .4472* .2649*

.1614 .2181" -.0074 .2524* .1864 .2522* .3346* .1731

Eating

Sleep

Sexual

Organic

.1558 .2669* .2048* .1623

.1372 .2406* .1450

.2909* .3898*

.5876*

.2946* .1003 .2234* .1669 .1822 .2365* .1196

SIB

-.0288 .1933 .0896 .3853* .3289* .3623*

*p < .001.

(Inappropriate Speech) to .9369 (Hyperactivity, Noncompliance)]. Cronbach alpha values for total scores were both high at .8688 for the DASH-H and .9470 for the ABC. Comparison of DASH-H factor scores with the ABC factor scores yielded very similar results (see Table 6). That is, the highest correlations (r ->.5000) were between the DASH-H Irritability and Hyperactivity factors with the ABC Emotional Lability and Antisocial factors. These factors were highly correlated within their respective subscales (see Tables 4 and 7). Also, the Emotional Lability and Antisocial factors encompass eight items of the Impulse Control subscale, which partially explains the similarity of results.

Table 4 Correlation Coefficients for A B C Subscales

Lethargy Stereotypies Hyperactivity Speech *p < .001.

Irritability

Lethargy

Stereotypies

Hyperactivity

.2738* .1840 .7797* .2687*

.3777* .3422* .0426

.2246* .0331

.3650*

DASH-II and ABC

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Table 5 Coefficient Alpha Values for Subscales and Tests

Alpha DASH-H Subscale Anxiety Depression Mania PDD/Autism Schizophrenia Stereotypies Self-injury Elimination Eating Sleep Sexual Organic Impulse Total

.4421 .5318 .6143 .5307 .5290 .5838 .4867 .5079 .2889 .2843 .4826 .5593 .8418 .8688

ABC Subscale Irritability Lethargy Stereotypic behavior Hyperactivity Inappropriate speech Total

.8894 .9245 .8818 .9369 .7872 .9470

DISCUSSION Our comparison of DASH-II subscales and ABC subscales revealed several relationships. First, the DASH-II as a whole has a high degree of convergent validity with the ABC total score, indicating that the DASH-H does address

Table 6 Correlation Coefficients for DASH-H and A B C Factors

ABC Factors DASH-llFactor Emotional lability Antisocial Language Social withdrawal Eating disorder Sleep disorder *p < .001.

Irritability .7176" .6858* .4859 .4043* .3275* .3026*

Lethargy .1681 .220l* .0342 .4571" .3020* .0616

Stereotypies Hyperactivity .2383* .1563 -.0549 .4830* .1901 .1554

.5593* .7070* .4525* .5491" .3449* .3629*

Speech .2151 .1149 .3925* .1896 .1889 .3546*

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Table 7 Correlation Coefficients for DASH-H Factors

Emotional Social Eating Lability Antisocial Language Withdrawal Disorder Antisocial Language Social withdrawal Eming disorder Sleep disorder

.5980* .4919" .4532* .2363* .2930*

.3779* .5219" .3190" .2858*

.2746* .3392* .2328*

.4820* .2020

.2960*

*p < .001. emotional and behavioral problems within the severely and profoundly mentally retarded population. Within the individual subscales, some DASH-H categories strongly correlated with A B C subscales while others did not, in part explained by subscale correlations within the instruments. The following patterns did emerge: (a) the A B C Irritability and Hyperactivity factors correlated strongly with each other and with the D A S H - H subscales of Depression, Mania, Organic Disorders, and Impulse Control Disorders; and (b) the A B C Stereotypic Behavior factor correlated highly with both the D A S H - H PDD/Autism and Stereotypies subscales. In terms of clinical application, it can be recommended that if there are elevations on the Irritability and Hyperactivity subscales of the ABC, an examiner should screen for possible Mood Disorders, Organic Disorders/Dementia, and Impulse Control/Conduct Disorders. Likewise, an elevation on the Stereotypic Behavior subscale of the A B C might lead an examiner to rule out pervasive developmental disorders, as well as Stereotypic Movement Disorder. The converse is also possible: an examiner using the A B C to track the treatment progress of a client with any of the above disorders may want to pay particular attention to the A B C subscales that correspond to these disorders. As to the remaining subscales, statistical methods may explain the lack of correlations. Sturmey and Bertman (1994) noted that poor psychometric structure may contribute to spurious correlation coefficients. In our calculation of coefficient alpha values, we obtained similar measures of internal consistency to Sevin et al. (1995). That is, the obtained values indicated fair consistency but some diversity within the subscales. In contrast, the alpha values for the A B C subscales were high, replicating earlier studies. This difference in subscale internal consistency is to be expected given that the DASH-H is taxonomydriven and the A B C is empirically-derived. Nonetheless, these scales when used together for clinical purposes should compliment one another nicely. While it may be argued that this difference diminishes the utility of the DASH-H, other areas need to be considered prior to such a conclusion. Specifically, base rates of the different disorders addressed by the DASH-H will affect the robustness of the instrument. For example, in a normative study of the

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DASH-I1, Hamilton (1995) found that 29.5% of the sample displayed repetitive

body movements but only 4.8% exhibited sleepwalking. Our sample yielded no participants with sleepwalking, which resulted in fewer items for analysis for that subscale. Some disorders, by virtue of their low prevalence rates, will be missed in a large-scale analysis. Einfield and Aman (1995) caution that statistical procedures such as factor analysis are not sensitive to variables occurring at low rates. Therefore, some of the low correlations between the subscales of the DASH-H and the ABC may reflect the wider and more varied diagnostic spectrum the DASH-H attempts to tap. In reviewing efforts to develop a reliable and valid taxonomy of psychopathology in mental retardation, Einfield and Aman (1995) list six general categories that seem to form a pattern of behavioral disorders in this population: (1) Aggressive, antisocial, self-injurious, (2) Withdrawal, (3) Stereotypic behavior, (4) Hyperactivity, (5) Repetitive Verbalizations, and (6) Anxious, Fearful, and Tense. These authors also identified the factors of several assessment tools for behavior disorders that corresponded to the above categories. The factor correlations listed in Table 4 support 4 of 6 of these content-based groupings. That is, significant correlations were observed in the following: (1) (Aggressive, antisocial, self-injurious) ABC Irritability and DASH-H Antisocial and Emotional Lability, (2) (Withdrawal)ABC Lethargy and DASH-H Social Withdrawal, (3) (Stereotypic Behavior) ABC Stereotypic Behavior and DASH-II Social Withdrawal, and (4) (Repetitive Verbalizations) ABC Inappropriate Speech and DASH-H Language Disorder. The correlation between the ABC Lethargy factor and the DASH-H Emotional Lability factor (grouped under Anxious, Tense, Fearful) was not significant, while the DASH-H did not have a factor to compare with the ABC Hyperactivity scale. To summarize, the DASH-H demonstrated overall convergent validity with the ABC in terms of total score and several factor scores. That is, the DASH-H does measure emotional and behavioral disturbance in severely and profoundly retarded persons and taps most of the major clusters of problems observed in the literature. While many of the subscales of the DASH-H did not correlate significantly with the ABC, it is likely that low base rates of these disorders prevented adequate statistical analysis. Future studies should emphasize a sufficient number and diversity of possible psychiatric disorders in the sample to better determine the validity of such disorders in the severely and profoundly retarded population.

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