Are Attentional-Hyperactivity Deficits Unidimensional or Multidimensional Syndromes? Empirical Findings from a Community Survey

Are Attentional-Hyperactivity Deficits Unidimensional or Multidimensional Syndromes? Empirical Findings from a Community Survey JOSE 1. BAUERMEISTER, PH.D., MARGARITA ALEG RIA, PH.D., HECTOR R. BIRD, M.D. , MARITZA RUBIO-STIPEC, M.A., AND GLORIS A CANINO, PH.D.

Abstract. Factor analysis on teacher ratings of symptoms in a probability com munity sample of children aged 6 to 16 years (N = 6 14) yielded two factors: Inattention and Hyperactivity-Impul sivity. Subsequent cluster analyses on the scores of factoria lly derived scales for a subsamp le of 170 children with a diagnosis of attention deficit disorder with (ADDH) and without hyperactivity (ADDWO), or norma ls, resulted in five clusters that accounted for 88% of the variance. The existence of these clusters was confirmed using external validating criteria. The data support a bidimen sional conceptualizatio n of attentio n deficit disorder with hyperactivity , one dimen sion consisting of symptoms of inattention and another of symptoms of hyperact ivity-impulsivity. The data also suggests that a condition very similar to the DSM-III-R description of undifferentiated attention-deficit disorder also exists as a distinct entity. J. Am . Acad. Child Adolesc. Psychiatry, 1992, 3 1, 3 :423~ 31 . Key Words: diagnosis, nosology, attention deficit disorder. Is attention deficit disorder (ADD) a unidim ensional or a multidimensional disorder? DSM-IIJ (American Psychiatric Associ ation, 1980) defined the cate gory of attention deficit disorde r with hyperactivity (ADDH) as three-dimen sional and as a disorder that purp ortedl y presents com binations of symptoms in the dom ains of inattention (three or more symptoms), impul sivity (three or more symptoms), and hyperactivity (two or more symptoms). The minimum number of symptoms in each of the three domains is necessary for the diagnosis to be present. DSM-III-R (American Psychiatric Association, 1987) describ es a unidimensional diagn osis, attention-defici t hyperactivity disorder (ADHD), which lists 14 possible symptoms, of which five seem to refer to inattention , five to impul sivity, and four to hyperactivity. The assumption is that there exis ts a single unitary dimension of mal adaptive beh avior that is manifested by all three: inattention, impulsivity, and hyperactivity (Lahey et a!., 1988). No specific set of symptoms in any one domain are requi red, and the presenc e of any 8 of 14 possible symptoms is neces-

Accepted December 27, 1991. Dr. Bauermeist er is Prof essor, Department of Psychology, University of Pue rto R ico. Dr. Al egri a is As sistant Prof essor of Publi c Health , University of Puerto Rico School of Public Health. Dr. Bird is Prof essor of Clinical Psychiatry , Columbia University, College of Physicians and Surgeons. Ms. Rubio-Stipec is Associate Prof essor of Economics and Dr. Canina is Associate Prof essor of Psychology, both in the Department of Psychiatry , University of Puerto Rico School of Medicin e. This pape r was presented at the 37th Annual Meeting of the Am erican Academy ofChild and Adol escent Psychiatry in Chicago, October 1990. The research was partially supported by grant MH-38821from the National Institu te of Mental Health. The authors wish to acknowledge the input p rovided by Benjamin Lahey, Ph.D., University of Miam i, and his careful comments about this paper, as well as that of Madelyn S. Gould, Ph.D., f rom Columbia University . The assistan ce of Jose Martinez in the analyses of the data is also gratef ully acknowledged. Reprint requests to Dr. Bauermeister, Psychology Department, University of Puerto Rico, Rio Piedras, PR 00931. 0890-8567/92/3 103-0423 $03.00/0©1992 by the American Academy of Child and Adolescent Psychiatry . J. Am.Acad. Child Adoles c. Psych iatry, 31:3, May 1992

sary and sufficie nt for the diagnosis. Thu s, symptoms in only two of the three domains would be sufficient for the diagnosis, provided that the total number of symptoms is eight or more. Theoret ically, a child could be classified as having ADHD without exhibiting symptoms of hyperactivity . Wh eth er thi s ind eed oc curs in the popul ation , is of course, an empirical question. Recent factor analytic studies of teach er ratings of children aged 6 through 13 years suggest that the symptoms of ADDH and ADHD covary independently in two dimensions: hyperactivity-impulsivity and inattention (Bauer meister, 1992; Hart et a!., submitted for publi cation; Healey et a!., 1987; Lahey et a!., 1988). Analyses of the hyperactivityimpul sivity and inattent ion factors extracted from teacher' s ratings of DSM-III symptoms (Lahey et a!., 1988) produced clusters that were associated with independent clinic al diagno ses of attention de fi cit disorder with hyperacti vity (ADDH) and attention deficit disorder without hypera cti vity (ADDWO). These find ings were replicated by Hart et a!. (unpublished manuscript ). The aforementioned studies, as well as a recent report by Newco m et a!. ( 1989), sugges t that application of DSM-III-R criteria of ADHD will result in the diagnostic categorization of a more hetero geneous group of children than the combination of those that would be included as ADDH and ADDWO. A rel ated issue is whe the r th e DSM-III ca tegory of ADDWO and the DSM-III-R category of undifferentiated attention-de ficit disorder (UADD) refer to the same disorder. In DSM-III, the ADDH and ADDWO subtypes share the same pattern of inatte ntiveness, impulsivity, and distractibilit y but differ in the hyperactivity domain (motor activity, restle ssness , and fidgetiness). However, DSM-III qualifies this categorization notin g that it is "not known whether ADDH and ADDWO are two forms of a single disord er or represent two distinct disorders" (p. 41). The DADD category is tentatively included in DSM-III-R to diagnose children who only exhibit symptoms of inattention, but neither the other symptoms nor the diagn ostic criteria are specified. The need for empirical research on the validity and defini-

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BAUERMEISTE R ET AL.

tion of this diagnostic category is emphasized. However, it should be noted that some of the manifestations of the DSMIII diagnosis of ADDWO would be included in the UADD category. There is a growing body of empirical evidence that supports the existence of ADDWO or UADD (Barkley et aI., 1990; Edelbrock et aI., 1984; Hynd et aI., 1991; King and Young, 1982; Lahey et aI., 1984, 1985, 1987). Generally, children who meet DSM-II1 criteria for ADDWO exhibit less serious conduct problems, are less impulsive, are less rejec ted by peers but more socially withdrawn, and are more likely to exhibit depressed mood and symptoms of anxiety disorder than ADDH/ ADHD children (Lahey and Carlson, 1991). Lahey et aI. (1984, 1985) have also provid ed evidence that the ADDH and ADDWO groups may also differ in the manifestations and characteris tics of the core attention deficits. Both group s were rated as exhibiting attention deficits similar to those of controls, on items referring to attention span, forgetfulness, difficulty in following directions, and immaturity. However, the ADDH group was described as more irresponsible, distractible, impulsive, prone to answering witho ut th in kin g , and mor e sloppy th an the ADDWO and the control groups. By contrast, the ADDWO group was rated as more sluggish and drowsy. More recently, Barkley et aI. (1990) reported that more ADDWO children were likely to have serious problems with being confused or " lost in a fog," daydreami ng, and being apathetic or unmotivated than were ADDH children. These findings seem to suggest that ADDH and ADDWO may exhibit qualitatively different patterns of attention deficits (Bark ley et aI., 1990; Lahey et aI., 1985). The aforementioned studies have used clinic-referred or no nrepresentative, schoo l-base d samples . None of them have investigated the validity of ADDWO or UADD in a nonclinical, representative sample drawn from the comm unity. As a result, the findings reported in previous investigations may not fully reflect the characteristics of this type of psychopathology in the population at large. Clinic al samples constitute a highly select and possib ly biased group. In general, referred children tend to be more impaired and to have higher levels of, and more severe, symptomatology; they are also more likely to have associa ted family difficulties and are skewed toward those socioeco nomic classes that value the uti liza tion of mental health care reso urces (Bark ley , 1990). The potential for bias precludes the generalizability of findings about psychopathology, from researc h on clinical samples to the genera l population. In the present report, two issues are examined using a community-based probabil ity sample: the issue of whether or not ADHD should be considered as a unitary, unidimensional syndrome, and the possible existe nce of ADDWO or UADD as a separate diagnostic entity. Method

Subjects and Overall Design

The data for the present study were obtained in a twostage epidemiological survey carried out on a probability sample of the populat ion aged 4 through 16 years in Puerto 424

Rico. The sampling procedures, design, and methodology of the Puerto Rico study have been reported (Bird et aI., 1988). In brief, a two-phase design was used, screeni ng children aged 4 through 16 years with the Child Behavior Checklist (CBCL) in the first phase (N = 777), and conducting a psychiatric evaluation in the secon d phase (N = 386) . Any child scoring over the normative thresholds of either the CBCL or the Teacher Report Form (TRF) (Achenbach and Ede lbrock, 1983, 1986) was co ns idered a positive screen. Targeted for the second phase were all childre n positive on the screen as well as 20% of the sample, regardless of the screening results. Because of some degree of noncompliance, 90% of those positive and 17% of those negative (i.e., 80% of the targeted subjects) on the screen were evaluated during the second phase. The second phase psychiatric evaluations included separate interviews with both the child and his/her parent. The child psychiatrists used the 1985 revision of the Diagnostic Interview Schedule for Children (DISC) (Costello et aI., 1987). Although the interviewee's responses to the DISC questions were coded, the DISC was used primarily as a sys te ma tic way of eliciting sy mpto m dat a. After interviewing both child and a parent, and reviewing a teacher narrative report, the child psychiatrists aggregated the information obtained to arrive at DSM -lIl clinical diagnoses. The time frame for the prese nce of symptomatic criteria was 6 months, so that all of the diagnoses could be considere d as "current." During a pilot study before the survey, clinicia ns had been found to agree on diagnostic assessments with an adequate level of reliability (Canino et aI., 1987). In the pilot study, test-retest interrater reliability for ADD among clinicians had a kappa of 0.54. Instruments and Measures

Lay intervie wers gathered information on family compo sition, demogr aphic data, and developmental history from the child's mother or mother surrogate. Among the measures of interest for the present report were scaled measures of marital disharmon y derived from the General Functioning scale of the McMaster Family Assess ment Device (Byles et aI., 1988; Epstein et aI., 1983), of family dysfunction (Del Vecchio et aI., 1979), and of stressful life events (Coddi ngton, 1972). Other risk factor variables were also collected (e.g., pregnancy and perinatal complications, delays in language development, health status, and others). The interviewer obtained the CBCL from the mother and the TRF and a short form of the School Behav ior Inventory-Revised (SBI-R) (Bauermeister, 1990) from the child's homeroom teacher. All of the measures were administered and coded by trained lay interviewers. In order to obtain a measure of impairment, the child psychiatrist gave each child a score on the Children' s Global Assessment Scale (CGAS) (Bird et aI., 1987, 1990; Shaffer et aI., 1983). Scores on the CGAS can range from 0 (severe impairment) to 100 (superior functioning). In the validation of the CGAS with the data from Puerto Rico, a cutoff score of 6 1 was found to be the best discriminator to distinguish between children who exhibited definite maladju stment and others (Bird et aI., 1987, 1990). J. Am.Acad. Ch ild Adolesc. Psychiatry, 31:3, May 1992

DIMENS IONS ATTENT IONAL- HYPERAC TIVITY SYNDROM ES

To construct a teac her rating scale of behaviors indicat ive of DSM-IlI-R ADHD and of ADDWOfUADD, a set of items that described symptom s of these disorders were drawn from the TRF and the SBI-R. Fro m these two instruments, a panel of two child psych iatrists and three psychologists independently selected II item s that best matched ADHD symp tom s. In addit ion, six item s descriptive of inattention/sluggishnes s in the classroom were added to the pool (ge ts tired too much , lazy, co nf us ed, apa theti c, un deract ive, and lacks persi stenc e) . Clini cal exper ience, as well as recent research (Bark ley et a!., 1990; Lahey et a!., 1985; Lahey et a!., 1988) suggest that these behaviors are part of an important dimension of ADDWOfUADD.

Analytic Strategy The 17 items were fac tor analyzed using principal co mponent s factor anal ysis with Yarimax rotation. Data from the 6 14 children aged 6 through 16 years who part icipated in the first stage of the epidem iological survey were used for this analysis. Fac tors with eige nvalues above 1.0 were extracted . To analyze the way in which children with cli nica l diagnoses of ADD and without any diagnosis clustered on the basis of these factors, Ward ' s (1963) cluster analysis was performed on the 170 subj ects fro m the second stage of the survey that met the ADDH and ADDWO diagnostic criteria, or who had no diagnosis. Finally, cluster differences in sociodemographic, clinical, fami ly, school , and deve lopmental variables were analyzed using univariate analyses of variance (AN OY AS) and chi-square tests. In view of the large numb er of statistica l tests, only result s having a probability value of p :s; 0.0 1 were considered statistically sig nificant to reduce the likelih ood of type I error. Whenever these analyses were significa nt, Newman-Keuls pairwise contrasts or chi-square tests (p :s; 0.05) were used to analyze potential gro up differences. Results Factor Analyses The factor anal ysis of the 17 items selected yielded two factors with eigen values above 1.0 (Ta ble I). The y have been labeled as Inattent ion and Hyperactivity-Impulsivity, based on the ir ite m co mposition. Th ese two fac tors ac counted for 59.3 % of the component variance. To examine the stability of the factor structure obtai ned for the total sam ple, the analyse s were replicated on three age groups of the same sample: children aged 6 throu gh 9 years (N = 22 1), those 10 through 12 years (N = 162), and those 13 throu gh 16 yea rs (N = 231) . Th e factor structure for eac h of these age groups was almost identical to the one obtained for the total sample. Two factor scales were constructed by selecting the item s with the highest loadings on the Inattention (I I item s) and the Hyperactivity-Impulsivity (6 items) fac tors. Cro nbac h's alpha coefficients and item-total correlations were computed for each scale. The result s provi de evidence for the internal reliability of the scales. Th e alpha coe fficient for the Inattention scale was 0.93, with itemtotal correlations ran ging from 0.51 to 0.77. Alph a for the Hyp eractivity-Impulsivity scale was 0.84, with item-t otal correlations ranging from 0.32 to 0.75. J. Am.Acad. Child Ado/esc. Psychiatry , 31:3, May 1992

T A BL E

I. Factor Loadings fo r the Teacher-Rated Descriptors of

AD HD and Inattention Symptoms

Items" Constantly movesbody or parts (hands, feet, etc.) (I ) Can't sit still, restless, or hyperactive (2) Easily distracts (3) Impulsive or acts without thinking (5) Difficulty following instructions (6) Can't concentrate, can't pay attention for long (7) Fails to fini sh things (8) Talks too much ( 10) Interrupts class ( I I) Stares blankly (12) Gets hurt a lot, accident prone (14)

Gets tired too much Lazy Confused or seems to be in a fog Apathetic and lacks motivation Underactive, slow moving, or lacks energy Shows lack of persistence

Inattention Factor

HyperactivityImpulsivity Factor

0.29

0.61

O. I I 0.73

0.83 0.35

0.22

0.74

0.73

0.31

0.77 0.74 O. I I 0. 17 0.77

0.27 0.29 0.8 1 0.84 0.02

0.09 0.45 0.76

0.42 0.4 1 0.30

0.75 0.77

0.2 1 0.23

0.76 0.78

0. 18 0.24

a Numbers in parentheses identify the correspondi ng DSM-lll-R symptom.

Cluster Analyses Scores on the two scales were subsequently com put ed for each of the 170 children in the second-stage sample who either met criteria for a DSM-lII diagnosis of ADDH (N = 56) or ADDWO (N = 20), or who did not meet criteria for any DSM-III diagnosis (N = 94) . These scores were subjected to a W ard ' s cl uster analysis (Everitt, 1980) to analyze the way in which children in this sam ple clu stered. Exa mination of the cubic clu stering criterion and clu ster dendrograms suggested that the childre n ca n be clas sified into either three or five clu sters. Th e three cluster solution lacked clea r clinicalor conc eptual sense. The five cluster solution yielded more meaningful profi les that acco unted for 88% of the variance . These five clusters were used in subse quen t ana lyses. The me an In attention an d Hyper act ivity-Impul si vi ty scores for the children in eac h clu ster, as well as for the total sam ple of 6 14 childre n, are presented in Table 2. The first clu ster (Hyperactive) was characterized by high hyperactivity-i mpulsivi ty and moderately high inattent ion scores; by contrast, cluster 2 (Inattentive) had very high inattent ion but very low hyperactivity-impul sivity scores, resemblin g the DSM-III-R, UADD catego ry; cluster 3 (Inattentive -Hyperactive) was characterized by high scores on both inattention and hyperactivity-impul sivity, and the profile resembl es the category of ADDH in DSM-III; cluster 4 (Normal) had

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BAUERMEISTER ET AL. TABLE

2. Mean Inattention and Hyperactivity Scale Scores for the Total Community Sample and Five Clusters of Children with DSM-III

Diagnoses of ADD or No Diagnoses Scale

N Inattention Scale

X SD Hyperactivity Scale

X SD

Cluster

Total Sample

H

I

IH

N

HA

614

15

15

42

36

62

7.08 6.21

11.33 1.35

17.87 2.45

16.57 2.24

9.42 2.50

1.87 1.72

2.54 2.90

8.47 1.41

.93 .80

7.24 2.10

2.28 2.04

1.56 2.13

Note: The range of possible scores for the Inattention Scale is 0 to 22; for the Hyperactivity Scale, the range is 0 to 12. H, Hyperactive; I, Inattentive; IH, Inattentive-Hyperactive; N, Normal; HA, Highly Adapted.

scores on both factors that approximate the total sample means; and finally, cluster 5 (Highly Adapted) had scores on both factors that were lower than the total sample mean. The means of the scales of Inattention and Hyperactivity of the five clusters were compared with the means of the total first stage sample (N = 614). In these comparisons, the subjects belonging to a given cluster were excluded from the computation of the total sample means. With the exception of the Inattention and Hyperactivity-Impulsivity scores in the Normal cluster, and the Hyperactivity-Impulsivity score in the Inattentive cluster, the mean scores of each of the clusters were significantly different from the total sample means (t values range from 2.70 to 12.12; df = 605; P :::; 0.01 two-tailed). Comparison of Inattention Scores

The Inattentive (I) and Inattentive-Hyperactive (IH) clusters had comparable mean Inattention scale scores (Table 2). In order to determine if these two clusters could be accurately discriminated on the basis of the type of inattention symptoms rated by the teacher, a stepwise discriminant function analysis was performed. A total of nine items contributed to the discriminant function. Using this function, 84% of the children were correctly classified. The I group had higher scores on the following items: underactive and slow moving, fails to finish things, apathetic and lacks motivation, stares blankly, can't concentrate, and lazy. The IH group had higher scores on: confused, gets tired too much, and show lacks of persistence. Thus, the I and the IH clusters can be distinguished not only on the basis of their mean hyperactivity and impulsivity scores, but on the rating of specific inattention items by the teachers as well. Relationship of the Clusters to Demographic Variables

Table 3 presents sex and socioeconomic (SES) data for the five clusters. Because the survey sample was predominantly of lower SES (Bird et al., 1988), Hollingshead classes I through IV were grouped together into a single category to increase the expected cell frequencies. There were significant differences between clusters in sex and SES, (X2 (4) = 17.39 and 17.63, respectively. A significantly smaller proportion of males were found in the Highly Adapted (HA) cluster. The proportion of children oflower SES was significantly greater in the Hyperactive (H) cluster than in the

426

other four. Similarly, a significantly greater proportion of children from the lower SES were also found in the IH cluster, relative to the Normal (N) and HA clusters. No significant differences in age among the clusters were found. Relationship of Clusters to Clinical Status DSM-III diagnoses and a continuous measure of impairment (the CGAS score), both provided by child psychiatrists, were used as measures of clinical status (Table 3). The diagnoses that were most prevalent in the survey results were aggregated into four major supraordinate categories following the scheme reported by Bird et al. (1988). This served to increase the expected cell frequencies in the chisquare tests. The four supraordinate diagnostic categories were: (1) attention deficit disorders, with and without hyperactivity; (2) affective disorders, consisting of major depressive disorder, dysthymic disorder, and cyclothymic disorder; (3) anxiety disorders, including separation anxiety disorder, the phobias, overanxious disorder, obsessive-compulsive disorder, panic disorder, and avoidant disorder; and (4) conduct/oppositional disorder encompassing those two categories. As indicated in Table 3, there were significant differences in the cluster proportions of the ADD, X2 (4) = 46.43, and the conduct/oppositional groupings, X2 (4) = 15.72. Children in the H, I, and IH clusters did not differ significantly on the percentage of ADD diagnoses received, but all three clusters had a significantly greater proportion of children with ADD diagnoses than the Nand HA groups. The HA cluster also had a significantly lower percentage of children with the conduct/oppositional disorder diagnosis, whereas the remaining four clusters did not differ in the frequency with which this disorder was diagnosed. There were no apparent differences among the clusters on the proportion of children with affective disorders, although the Hand IH clusters seemed to have more children with anxiety disorders. However, significance testing was not possible for these two categories due to the small numbers of children in the various cells. This same limitation precluded a chisquare analysis for the breakdown between the ADDH and ADDWO diagnostic categories. Approximately 73% of the children in the H cluster and 60% in the IH cluster received ADDH diagnoses. The children in the I cluster were equally likely to receive ADDH, ADDWO, or no diagnoses. Finally, 64% of the children in the N cluster and 84% in the HA J. Am. Acad. Child Adolesc. Psychiatry, 3 I: 3, May 1992

DIMENSIONS ATTENTIONAL-HYPERACTIVIT Y SYNDR OMES

TABLE 3. Summa ry of Pattern of Cluster Correlates: Demographic Variables, Clinical Status, CBCL and TRF Scores, and Developmental Variables Cluster Variable Demographic variables Sex (males)" Lower SEsa Clinical status ADD Conduct/oppositional disor der X CGAS Score" CBCL scales Aggressive" Delinquen t" Hyperac ti ve" Total problems" School perform ance Grade failure" TRF Socia l withdrawal" Unpop ular!' Anxiou s" Aggressiveb Self-destructi ve" Total problems" Developmental variables Pregnancy comp lications" Language development" Slower or much slower

H

IH

N

HA

Comparisons among Clusters

80.0 73.3

60.0 21.4

69.0 43.9

6 1.1 22.9

35.5 24.6

H, IH, N> HA H > I, IH, N, HA ; IH > N, HA

80.0

66.7

73.8

36. 1

16.1

H, I, IH > N > HA

33.3 59.60

33.3 62.13

35.7 59.29

27.8 72.8 1

6.5 78. 15

H, I, IH, N > HA H, I, IH < N < HA

66.80 63.73 68.80 66.20

66.60 63.67 68.13 67.00

70.09 67. 14 7 1.26 70.29

63.69 62.50 62.39 6 1.31

62.50 59.98 60.48 60.05

IH > IH > I, H, IH >

46.7

33.3

54.8

16.7

3.2

6 1.27 63.73 63.20 65.73 63.53 66.60

76.60 62.07 60.80 56.60 60.33 63.20

70.62 67.10 65.93 68.57 65.07 7 1.76

63.44 59.3 1 58.89 57. 19 59.83 57.6 1

58.44 57.32 58.60 56.60 58.32 50.79

I > IH > H, N, HA; N > HA IH> I, N, HA; H > N, HA; I > HA IH > I, N, HA; H > HA H, IH > I, N, HA H, IH > N, HA; IH > I IH > H, I > N > HA

40.0

21.4

7 1.8

44.4

48.4

IH > H, I, N, HA

6.7

40.0

41.0

8.3

11.3

I, IH > H, N, HA

N, N, IH N,

HA HA > N, HA HA

H, IH > N, HA; I, N > HA

Note: With the exception of CGAS, CBC L, and TRF scores, data are expressed in percentages. H, Hyperactive; I, Inattent ive; IH, Inattentive-Hyperactive; N, Normal ; HA, Highly Adapted; CGAS , Children' s Global Assess ment Scale; CBCL, Child Behavior Checkli st. Comp arisons among clusters are the results of pair wise contrasts using Newman-Keuls or chi-square tests in which a contra st reached statistical significance (p < 0.05). a p < 0.01 for analyses based on chi-sq uare tests. b p < 0.0 I for univariate ANOV AS.

cluster did not receive any DSM -Ill diagnoses. In summary, when diagnosis is used as a correlate there is no distinct pattern that distinguishes the three " disorders" clusters (I, IH, H) from each other, even though they do differ from the normal (N) and the highly adapted HA clusters. Signific ant differen ces were obtai ned fo r the CGA S scores, F(4 ,165) = 24.08. In pairwise comparisons, the H, I, and IH clusters had comparable CGAS scores, all of which were significantly (p ~ 0.05) lower (i.e., in the more impaired range) than those of the Nand HA clusters. Relationship of Clusters to Relevant Scales on the CBCL Cluster similarities and differences on the Aggressive, Delinquent, Hyp eractive, and Tot al Beha vior Problem (TBP) scores of the CBCL were compared using ANOVAS. These CBCL scales were selected for analysis because they contai n similar items for both ge nde rs and the two age groupings (6 to 11; 12 to 16 years) under investigation. Following the method recommended for combining samples of different sex and age in the same dimension (Achenbach and Edelbrock, 1986, p. 128), the raw scores on these scales were converted to T scores based on the norms for their sex J. Am .A cad. Child Adolesc. Psychiatry, 31:3, May 1992

and age. This procedure permits the analyses of T scores combining children of more than one sex/age group on analogous factors of the CBCL. Significant differences among the clusters were found for the Aggressive, Delinquent, Hyperactive, and TBP scales, F(4,165) = 4.84, 7.95, 11.67, and 7.02, respectively. Subsequent pairwise comparisons indicate that only the IH cluster obtained significantly higher scores on the Aggressive, Delinquent, and TBP scales than the Nand HA clusters (Table 3). Children classified in the H, I, and IH clusters obtained significantly higher scores on the Hyperactive CBCL scale than those classified in the N and HA clusters; nevertheless, the first three and the latter two did not differ significantly among themselves. This finding is not surprising since the CBCL Hyperactive scale includes several items related to inattention and to hyperactivity. Relationship of Clusters to School Variables Failing a grade was significantly associated, X2 (4) = 40.84, with the clusters (Table 3). The proportion of children who had failed a grade was significantly greater in the H and IH clusters than it was in the Nand HA clusters. The I 427

BA UERMEISTER ET A L.

and N clusters did not differ significantly on this proportion but were signific antly different from the HA cluster, which had the lowest rate of grade failure. TRF T scores were computed for those scales that have common items in the same dimension for the age/sex groups studied followin g the method recommended by Achenbach and Edelbrock (1986, p. 128). Since the clusters were identified based on teacher rating s of inattention and hyperactivity-impul sivity items, it is expected that other teacher ratings of variables that covary with the clustering criteri a will also relate to the clusters. However, such analyses are useful to demonstrate the range of behavior problems associated with high levels of inattention and hyperactivity (Barkley et aI., 1990). As expected, the five clusters showed significant differences in the scores of the Social Withdrawal, Unpopul ar, Anxious, Aggressive, Self-Destructive, and TBP scales of the TRF; F(4,165) = 42.93,1 9.76,10.74,35.70,10.06, and 8 1.74, respectively. Pairwise comparisons (Table 3) indicated that children in the I cluster had significantly higher scores on the Social Withdrawal scale than children in the lH cluster, who in tum , had significantly higher scores on this scale than children in the other three clusters. Children in the IH group had significantly higher scores than children in the I, N, and HA clusters, on the Unpopular, Anxious, Aggressive, Self-Destructive, and TBP scales; they also had significantly higher scores on the TBP scale than children in the H group. With the exception of the Social Withdrawal scale, the H group had significantly higher scores on the other TRF scales than did the N or HA clusters, and significantly higher scores on the Aggressive scale than children in the I cluster. The five clusters differed significantly on the scores obtained in the Language, Memory, and Reading scales of the revised School Behavior In ventory, F(4,165) = 32 .5 1, 46.70, and 35.54, respectively . In general, subsequent pairwise comparisons indicate that the H, I, and IH clusters did not differ significantly on these measures but were rated as presenting more difficultie s on these scales than the N or HA clusters. Children in the I cluster presented a significantly higher level of reading difficulties than those in the IH cluster. Relation ship of the Clusters to Early Developm ental and Family Related Variables

The examination of the possible relationship between the clusters and other measures was restricted to those variables for which some type of association could be anticipated on conceptual grounds. Table 3 includes those variables for which significant associations were found . Maternal reports of pregnancy complications and of delays in language development were the only early developmental variables significantly related with the clusters extracted, X2 (4) = 13.09 and 22.39, respecti vely. Approximately 72% of the mothers of the children in the IH cluster reported complication s during pregnancy. Pregnan cy complications included those that are considered to be of salient importance by both obstetricians and pediatricians (e.g., albuminuria, hypertension, first trimester bleeding, etc.). The proportion of pregnancy compl i-

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cations present in the IH cluster is significantly higher than that reported for the other clusters. The proporti on of mothers reporting that their children learned to speak and to use language for communication later than other children was significantly greater in the I and lH clusters than in the other three groups. No significant differences were found among the clusters in relationship to the variables measuring perinatal complications and the child's general health status. Four famil y related variables were con sid ered : sca led measures of marital harmony, overall family dysfunction and stressful life events, and a categorical measure related to single parentho od. ANOVAS were conducted for the scores on each of the three scaled measures, and no significant differences among the clusters (p < 0.05) could be detected. Membership in the five clusters was not associated (X2 ) with single parenth ood. Discussion The goals of the present study were to examin e whether teacher ratings of items that match ADHD symptoms and other items related to inattention organize into single or multiple dimensions of maladaptive behavior, and to explore the possible existence of ADDWOIUADD as a separate diagnostic category. The factor analysis of teacher ratings yielded two factors. The first factor encomp asses inattention-distractibility symptoms of ADHD (e.g., eas ily distracts, difficulty following instructions, fails to finish things) and items that are conceptually related to behaviors associated in previous research with ADDWO (e.g., lazy, confused, apathetic , underactive or slow moving) (Lahey et aI., 1985, 1987). The second factor consists of ADHD hyperactivity-impul sivity symptoms (e.g., constantly moves body, restless or hyperact ive, impulsive or acts without thinking, talks too much, interrupts). The Inattention and Hyperactivity-Impulsivity factors replicated when the analyses were performed for three age groups (6-9, 10-12, and 13-1 6 years), a finding that supports the stability of the factor structure obtained for the entire range (6-16 years). These findings concur with th ose reported by other re search (Bauermeister, 1992; Healey et aI., 1987; Lahey and Carlson, 1991; Lahey et aI., 1988). The data do not provide empirical support to favor a unidimensional definiti on of ADHD, such as the one proposed in DSM-lll-R; in fact, the symptoms of the disorder are organized into two relatively independent dimensions. The findings do support the DSMIll-R definition of UADD, since a number of children were classified into a cluster of symptoms that were found to be present in the absence of hyperactivity and impulsivity. Finally, the data do not support the DSM-Ill conceptualization of ADDWO . The explicit criteria for the latter disorder were symptoms of inattention and impulsi vity, but not hyperactivity. The present findings, and those reported by the investigators cited (Bauermeister, 1992; Healey et al., 1987; Lahey and Carlson, 1991; Lahey et aI., 1988), demonstrate that items describing overt impulsivity do not load together with the inattent ion factor but rather with the hyperactivityimpulsivity factor. Cluster analysis was performed on the Inattention and Hyperactivity-Impulsivity factor scores in order to examine J. Am. A cad. Child Ado lesc. Psychiatry, 31:3, May 1992

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the profiles of children who had been diagnosed in the survey as ADDH, ADDWO, or normals. The children in the H, I, and IH clusters showed more clinical impairment than the N and HA group s. A considerable proportion of children in the first three clusters met the criteria for DSM-III attention defici t disorders (and, to a lesser degree, other diagnoses); had a CGAS score in the definitely impaired range « 6 1) (Bird et aI., 1987; Bird et aI., 1988); had repeated a grade in school; and were rated by their teachers as presenting memory, language, and reading difficulties. Although children in the three "clinical" clusters all meet similar criteria of maladjustment, they appear to present a different pattern of correlates that support their discriminant validity and have potential theoretical and clinical implications. The present findings suggest that the Inattentive and Inattentive-Hype ractive cluster s represent two distinct syndromes consisting of children who appear to exhibit ADDH and ADDWOIUADD, respectively. The Inattentive-Hyperactive children are significantly more active and impulsive, have a higher rate of reported pregnancy complications in their prenatal history, and are rated by teachers as significantly more unpopular, anxious, aggressive, self-destructive, and with more total behavior problems than the Inattentive, Normal, and Highly Adapted groups. The Inattentive-Hyperactive children are also rated by parents as more aggressive, delinquent, and with more total behavioral problems than the Normal and the Highly Adapted groups. The Inattentive group was rated by teachers as more socia lly withdrawn than the other groups and as having more reading difficulties than children in the Hyperactive-Impulsive cluster. It is of interest that comparable findings on parent and/ or teacher ratings have been reported in the studies in which children classi fied as ADDW and ADDWO on the basis of teacher ratings (Barkley et aI., 1990; King and Young, 1982; Lahey et aI., 1984) or on the basis of clinical diagnoses (Edelbrock et aI., 1984; Lahey et al., 1987) have been contrasted. In some of these studies, as in others report ed in the literature (Barkley et aI., 1990; Biederman et aI., 1987; Hynd et aI., 1991; Mun ir et aI., 1987), ADDH children have been fou nd to be more like ly to receive the codiag nosis of conduct/oppositional disorder. In the present study, the Inattentive-Hyperactive cluster, which is the one that most resembles ADDH in symptomatology, contained only a slightly higher proport ion of children with conduct/oppositional disorder, but this proportion was not significantly different from what it was in the Inattentive, Hypera ctive, or Norm al groups. This finding may be explained by the extremely higher degree of comorbidity between the conduct/oppositional diagnoses and all other diagnoses reported in the survey and by the low prevalence of pure conduct/oppositional disorders (Bird et al., 1988). The Inattentive-Hyperactive group, however, appears to display a pattern of more aggressive and delinquent behaviors at home and/or school. Altho ugh the Inatt enti ve and In att entive-H yperact ive clusters have similar levels of deviance on inattention, the results of the discriminant function analysis suggest that the two groups represent qualitatively different disorders. The Inattentive group presented a profile of higher ratings of J. Am. Acad. Child Ado/esc. Psychiatry, 31:3, May 1992

" underactivity or movin g slow ly, " " fai lure to finis h things," " apathy," " blank staring," " concentration prob lems," and "laziness," and lower ratings on " confusion" and "getting tired too much ." There is similarity between these finding s and th ose of Lah ey et al. (198 5, 1987 ), wherein ADDWO children are more sluggish and drowsy than ADDH children. The Inattentive and Inattentive-Hyperactive clusters do not differ significantly among themselves, nor from the other three clusters, on the family risk factor measures (marital harmony, overall fami ly dysfu nct ion , and stressful li fe events). Similar findings for ADDH and ADDWO groups of children have been reported by Barkley et aI. (1990). The proportion of children with reported delays in language development was significantly greater in the Inattentive and Inatten tive-Hyperacti ve clu sters tha n in the othe r three groups. These data are of particular interest in view of the findings from other community-based samples that ADDH childre n are more likel y to be del ayed in lan gu age and speec h acquisition tha n norm al children (Har tso ugh and Lambert, 1985; Stewart et aI., 1966; Szatmari et aI., 1989). The data suggest that the ADDWOIUADD child may also present a similar history. Furthermore, the findings suggest that language delay is an important antecedent of inattentive behaviors, since children in the pure Hyperacti ve cluster did not present such delays. Children in the Hyperactive cluster are characterized by moderately high inattention scores and high hyperac tivity scores, and they also appear to exhibit ADDH. This group of children, however, present a pattern of correlates that is different from that of the Inattentive-Hyperactive children: it included the highest proportion of males and children of lower SES. The children in the Hyperactive cluster were rated by their teachers as less socia lly withdraw n than those in the other two clinical clusters and were rated similarly to the Inattenti ve-Hyperactive group on the other behavior scales, with the exception of the total behavior problem scale. They were rated by their parents to be as hyperactive as the children in the Inattentive and Inattentive-Hyperactive clusters. Further research is needed to understand the clinical significance of the Hyperactive group defined here, particularly when two other studies have also identified a less clearly inatte ntive but hyperactive- impulsive gro up from teacher ratings of ADHD symptoms. (Bauermeister, 1992; Newcorn et aI., 1989). It is conceivable that children of low SES present a behavior al style of overactivity and impulsivity in the classroom setting that is associated with their socialization experiences and parenting styles rather than with impaired attention. Understandably, the level of agreement between the clinicians' ADDH and ADDWO diagnoses and applicable cluster membership was not high, particularly for the ADDWO diagnoses. The cluster analysis was based on teacher ratings of inattention and hyperactivity-impulsivity symptoms in the classroo m setting. The diagnoses, however, were based on DSM -III symptoms elicited from the parents and children using the DISC. Since DSM -1I1 symptoms for inattention, hyperactivit y, and impulsivity do not cluster into dimensions that correspond to the three DSM-llI criteri a, diagnosing

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children on the basis of these criter ia may result in relatively impure groups of ADDH and ADDWO (Barkley et al., 1990; Lahey et al., 1988). Furthermore, the clinicians were blind to the CBCL, TRF , or SBI-R scores, and thus had no information about ratings of a number of behaviors of interest in other situations. The findings of the present study are the first to support the discriminant validity of the ADDWOIUADD diagnosis in a community sample. These findings respond to the main purpose of the study, namely, whether attentional deficits are unidimensional or multidimensional constructs and whether ADDWO/UADD e xis ts as a se p ara te dia gn osi s fro m ADDH. Further research is now needed on the specificity ofthe ADDWOIUADD diagnosis with respect to other diagnoses (Werry et al., 1987). The issue could be raised of whether the cluster solution chosen can be considered perform ance clusters and groups of children that are quantitati vely but not qualitat ively different. However, the pattern of cluster correlates for the development al variables studie d and the different profil es of inattention symptoms among the Inattentive and InattentiveHyperactive groups argue against this possibility. This is a Hispanic sample, representative of the children in Puerto Rico. The levels of psychopath ology in this sample appeared to be different to those of mainland samples; similarly, the pattern s of psychop athology could also be different. Although several of the findings in this study are similar to those reported for U.S. samples (Lahey and Carlson, 1991), the generalizability of these findings is an issue that can only be settled if the results are replicated in another sample. Certain methodological limitations must be kept in mind. The relatively small number of children in both the Inattentive and Hyperactive clusters preclud ed analyses of additional measures of interest and limited the statistical power to detect potenti al cluster differe nces. In addition, cognitive measures were not available on the children studied. Should systematic differences in intellectual ability exi st across group s, cognitive level could have contributed to the differences found on other measures. Notwithstanding these limitations, there are implications from these findings for the conceptualization and definiti on of the attention deficit disorders in DSM-IV. First, these data, and those reported by other investigators (Bauermeister, 1992; Healey et al., 1987; Lahey and Carlson, 1991; Lahey et al., 1988) suggest that for children aged 6 through 16 years, a distinct bidimensional entity exists. In this conceptualization, symptoms of both inattention and of hyperactivity-impulsivity are necessary for a diagnosis to be present. This definition results in the classification of a narrower but more clinically homogeneous group of children who are both hyperacti ve and inattentive. In conceptualizing the disorders, DSM-IV will need to take into account age and developmental stages. Recent findings from factor analysis of teacher ratings suggest that for children aged 4 and 5 years of age, ADHD symptoms appear to covary in a single dimension (Bauermeister, 1992). Second, the data suggest that an attention deficit syndrome without symptoms of hyperactivity or impulsivity, similar to the DSM-III-R description of UADD, exists as a distinct behavioral syndrom e observable in the school setting. Un430

deractivity, failure to finish things, apathy, blank staring, and drowsine ss appear to be some of the manifestations of this syndrome. These data, and the findings reported by Lahey et a1. (1984, 1985, 1987, 1988), suggest that this type of attention deficit should continue to be considered a separate diagnostic category in DSM-IV. Finally, the finding that children rated as moderately inattentive and hyperactive (the Hyperactive Cluster) present a distinct pattern of correlates raises questions about the possible existence of still another subtype. DSM-I V needs to develop a more explicit operationalization of criteria as well as separate continuous measures of inattent ion and hyperactivity to assist in the diagnosis of possible ADD subtypes. Properl y normed continuous measures of teacher or parent ratings of ADDH or ADDWOIUADD symptoms can provide necessary clinical and statistical means to assess deviant behavi ors and symptoms of development ally inappropriate inattenti on and hyperactivity-impul sivity (Barkley, 1990).

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