9
Are Attentional-Hyperactivity Deficits Unidimensional or Multidimensional Syndromes? Empirical Findings from a Community Survey JOSE 1. BAUERMEIS TER, PH.D., MARGARITA ALEGRIA, PH.D., HECTOR R. BIRD, M.D., MARITZA RUBIO-STIPEC, M.A., AND GLORISA CANINO, PH.D. Abstract. Factor analysis on teacher ratings of symptoms in a probability community sample of children aged 6 to 16 years (N = 614) yielded two factors: Inattention and Hyperactivity-Impulsivity. Subsequent cluster analyses on the scores of factorially derived scales for a subsample of 170 children with a diagnosis of attention deficit disorder with (ADDH) and without hyperactivity (ADDWO), or normals, 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, 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 category of attention deficit disorder with hyperactivity (ADDH) as three-dimensional and as a disorder that purportedly presents combinations of symptoms in the domains of inattention (three or more symptoms), impulsivity (three or more symptoms), and hy- peractivity (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 Psychiat- ric Association, 1987) describes a unidimensional diagnosis, attention-defici t hyperactivity disorder (ADHD), which lists 14 possible symptoms, of which five seem to refer to inatten- tion, five to impulsivity, and four to hyperactivity. The as- sumption is that there exists a single unitary dimension of maladaptive behavior that is manifested by all three: inatten- tion, impulsivity, and hyperactivity (Lahey et a!., 1988). No specific set of symptoms in any one domain are required, and the presence of any 8 of 14 possible symptoms is neces- Accepted December 27, 1991. Dr. Bauermeister is Prof essor, Department of Psychology, Univer- sity of Puerto Rico. Dr. Alegria is Assistant Prof essor of Publi c Health , University of Puerto Rico School of Public Health. Dr. Bird is Professor of Clinical Psychiatry, Columbia University, College of Physicians and Surgeons. Ms. Rubio-Stipec is Associate Professor of Economics and Dr. Canina is Associate Professor 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 Ameri- can Academy of Child and Adolescent 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 acknowl- edge the input provided by Benjamin Lahey, Ph.D., University of Miami, and his car ef ul 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 acknowl- edged. Reprint requests to Dr. Bauermeister, Psychology Department, Uni- versity of Puerto Rico, Rio Piedras, PR 00931. 0890-8567/92/3103-0423$03.00/0©1992 by the American Acad- emy of Child and Adolescent Psychiatry. J. Am.Acad.Child Adolesc. Psychiatry, 31:3, May 1992 sary and sufficient 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. Theoretically, a child could be classified as having ADHD without exhibiting symptoms of hyperactiv- ity. Whether this indeed occurs in the popul ation , is of course, an empirical question. Recent factor analytic studies of teacher ratings of chil- dren aged 6 through 13 years suggest that the symptoms of ADDH and ADHD covary independently in two dimen- sions: hyperactivity-impulsivity and inattention (Bauermeis- ter, 1992; Hart et a!., submitted for publication; Healey et a!., 1987; Lahey et a!., 1988). Analyses of the hyperactivity- impulsivity and inattention factors extracted from teacher's ratings of DSM-III symptoms (Lahey et a!., 1988) produced clusters that were associated with independent clinical diag- noses of attention defi cit disord er with hyperacti v ity (ADDH) and attention deficit disorder withou t hyperactivity (ADDWO). These findings were replicated by Hart et a!. (unpublished manuscript). The aforementioned studies, as well as a recent report by Newcom et a!. (1989), suggest 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 ate d is sue is whether the DSM-III ca t egory of ADDWO and the DSM-III-R category of undifferentiated attention-deficit disorder (UADD) refer to the same disor- der. In DSM-III, the ADDH and ADDWO subtypes share the same pattern of inattentiveness, impulsivity, and distract- ibility but differ in the hyperactivity domain (motor activity, restle ssness, and fidgetiness). However, DSM-III qualifies this categorization noting that it is "not known whether ADDH and ADDWO are two forms of a single disorder or represent two distinct disorders" (p. 41). The DADD cate- gory is tentatively included in DSM-III-R to diagnose chil- dren who only exhibit symptoms of inattention, but neither the other symptoms nor the diagnostic criteria are specified. The need for empirical research on the validity and defini- 423

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

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

JOSE 1. BAUERMEISTER, PH.D., MARGARITA ALEGRIA, PH.D., HECTOR R. BIRD, M.D. ,MARITZA RUBIO-STIPEC, M.A., AND GLORISA CANINO, PH.D.

Abstract. Factor analysis on teacher ratings of symptoms in a probability community sample of childrenaged 6 to 16 years (N = 614) yielded two factors: Inattention and Hyperactivity-Impul sivity. Subsequent clusteranalyses on the scores of factoria lly derived scales for a subsamp le of 170 children with a diagnosis of attentiondeficit disorder with (ADDH) and without hyperactivity (ADDWO), or norma ls, resulted in five clusters thataccounted 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 sionconsisting of symptoms of inattention and another of symptoms of hyperact ivity-impulsivity. The data also suggeststhat a condition very similar to the DSM-III-R description of undifferentiated attention-deficit disorder also existsas 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 amultidimensional disorder? DSM-IIJ (American PsychiatricAssoci ation, 1980) defined the category of attention deficitdisorde r with hyperactivity (ADDH) as three-dimensionaland as a disorder that purportedl y presents combinationsof symptoms in the domains of inattention (three or moresymptoms), impul sivity (three or more symptoms), and hy­peractivity (two or more symptoms). The minimum numberof symptoms in each of the three domains is necessary forthe diagnosis to be present. DSM-III-R (American Psychiat­ric Association, 1987) describes a unidimensional diagn osis,attention-defici t hyperactivity disorder (ADHD), which lists14 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 ofmaladaptive behavior that is manifested by all three: inatten­tion, impulsivity, and hyperactivity (Lahey et a!., 1988). Nospecific 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. Bauermeister is Prof essor, Department ofPsychology, Univer­

sity of Puerto Rico. Dr. Al egri a is As sistant Prof essor of Publi cHealth , University of Puerto Rico School of Public Health. Dr. Birdis Prof essor of Clinical Psychiatry , Columbia University, College ofPhysicians and Surgeons. Ms. Rubio-Stipec is Associate Prof essor ofEconomics and Dr. Canina is Associate Prof essor ofPsychology, bothin the Department of Psychiatry , University of Puerto Rico School ofMedicin e.

This pape r was presented at the 37th Annual Meeting of the Ameri­can Academy ofChild and Adolescent Psychiatry in Chicago, October1990. The research was partially supported by grant MH-38821fromthe National Institu te of Mental Health. The authors wish to acknowl­edge the input provided by Benjamin Lahey, Ph.D., University ofMiami, and his careful comments about this paper, as well as that ofMadelyn S. Gould, Ph.D., f rom Columbia University . The assistan ceof 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.

0890-8567/92/3103-0423$03.00/0©1992 by the American Acad­emy of Child and Adolescent Psychiatry .

J. Am.Acad. Child Adolesc. Psychiatry,31:3,May 1992

sary and sufficie nt for the diagnosis. Thu s, symptoms inonly two of the three domains would be sufficient for thediagnosis, provided that the total number of symptoms iseight or more. Theoret ically, a child could be classified ashaving ADHD without exhibiting symptoms of hyperactiv­ity . Wh eth er thi s ind eed oc curs in the population , is ofcourse, an empirical question.

Recent factor analytic studies of teacher ratings of chil­dren aged 6 through 13 years suggest that the symptoms ofADDH and ADHD covary independently in two dimen­sions: hyperactivity-impulsivity and inattention (Bauermeis­ter, 1992; Hart et a!., submitted for publication; Healey eta!., 1987; Lahey et a!., 1988). Analyses of the hyperactivity­impul sivity and inattent ion factors extracted from teacher ' sratings of DSM-III symptoms (Lahey et a!., 1988) producedclusters that were associated with independent clinical diag­no ses of attention defi cit disorder with hyperacti vity(ADDH) and attention deficit disorder without hyperactivity(ADDWO). These findings were replicated by Hart et a!.(unpublished manuscript ). The aforementioned studies, aswell as a recent report by Newco m et a!. (1989), sugges tthat application of DSM-III-R criteria of ADHD will resultin the diagnostic categorization of a more hetero geneousgroup of children than the combination of those that wouldbe included as ADDH and ADDWO.

A rel ated issue is whe ther th e DSM-III ca tegory ofADDWO and the DSM-III-R category of undifferentiatedattention-de ficit disorder (UADD) refer to the same disor­der. In DSM-III, the ADDH and ADDWO subtypes sharethe same pattern of inattentiveness, impulsivity, and distract­ibilit y but differ in the hyperactivity domain (motor activity,restle ssness , and fidgetiness). However, DSM-III qualifiesthis categorization noting that it is "not known whetherADDH and ADDWO are two forms of a single disorder orrepresent 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 neitherthe other symptoms nor the diagn ostic criteria are specified.The need for empirical research on the validity and defini-

423

BAUERMEISTE R ET AL.

tion of this diagnostic category is emphasized. However, itshould be noted that some of the manifestations of the DSM­III diagnosis of ADDWO would be included in the UADDcategory.

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 andYoung, 1982; Lahey et aI., 1984, 1985, 1987). Generally,children who meet DSM-II1 criteria for ADDWO exhibitless serious conduct problems, are less impulsive, are lessrejec ted by peers but more socially withdrawn, and are morelikely to exhibit depressed mood and symptoms of anxietydisorder than ADDH/ADHD children (Lahey and Carlson,1991). Lahey et aI. (1984, 1985) have also provided evi­dence that the ADDH and ADDWO groups may also differin the manifestations and characteris tics of the core attentiondeficits. Both groups 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 describedas more irresponsible, distractible, impulsive, prone to an­swering witho ut th in kin g , and mor e sloppy th an theADDWO and the control groups. By contrast, the ADDWOgroup was rated as more sluggish and drowsy. More re­cently, Barkley et aI. (1990) reported that more ADDWOchildren were likely to have serious problems with beingconfused or " lost in a fog," daydreaming, and being apa­thetic or unmotivated than were ADDH children. Thesefindings seem to suggest that ADDH and ADDWO mayexhibit qualitatively different patterns of attention deficits(Barkley et aI., 1990; Lahey et aI., 1985).

The aforementioned studies have used clinic-referred ornonrepresentative, school-base d samples . None of themhave investigated the validity of ADDWO or UADD in anonclinical, representative sample drawn from the commu­nity. As a result, the findings reported in previous investiga­tions may not fully reflect the characteristics of this type ofpsychopathology in the population at large. Clinical samplesconstitute a highly select and possib ly biased group. In gen­eral, referred children tend to be more impaired and to havehigher levels of, and more severe, symptomatology; they arealso more likely to have associa ted family difficulties andare skewed toward those socioeco nomic classes that valuethe uti liza tion of mental health care reso urces (Bark ley ,1990). The potential for bias precludes the generalizabilityof findings about psychopathology, from research on clinicalsamples to the genera l population. In the present report, twoissues are examined using a community-based probabil itysample: the issue of whether or not ADHD should be consid­ered as a unitary, unidimensional syndrome, and the possibleexistence of ADDWO or UADD as a separate diagnosticentity.

Method

Subjects and Overall Design

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

424

Rico. The sampling procedures, design, and methodologyof the Puerto Rico study have been reported (Bird et aI.,1988). In brief, a two-phase design was used, screeni ngchildren aged 4 through 16 years with the Child BehaviorChecklist (CBCL) in the first phase (N = 777), and conduct­ing a psychiatric evaluation in the second phase (N = 386) .Any child scoring over the normative thresholds of eitherthe CBCL or the Teacher Report Form (TRF) (Achenbachand Ede lbrock, 1983, 1986) was co nsidered a positivescreen. Targeted for the second phase were all childre npositive on the screen as well as 20% of the sample, regard­less of the screening results. Because of some degree ofnoncompliance, 90% of those positive and 17% of thosenegative (i.e., 80% of the targeted subjects) on the screenwere evaluated during the second phase.

The second phase psychiatric evaluations included sepa­rate interviews with both the child and his/her parent. Thechild psychiatrists used the 1985 revision of the DiagnosticInterview Schedule for Children (DISC) (Costello et aI.,1987). Although the interviewee's responses to the DISCquestions were coded, the DISC was used primarily as asys tema tic way of eliciting sympto m data. After inter­viewing both child and a parent, and reviewing a teachernarrative report, the child psychiatrists aggregated the infor­mation obtained to arrive at DSM -lIl clinical diagnoses. Thetime frame for the presence of symptomatic criteria was 6months, so that all of the diagnoses could be considere d as"current." During a pilot study before the survey, clinicianshad been found to agree on diagnostic assessments with anadequate level of reliability (Canino et aI., 1987). In thepilot study, test-retest interrater reliability for ADD amongclinicians had a kappa of 0.54.

Instruments and Measures

Lay interviewers gathered information on family compo ­sition, demographic data, and developmental history fromthe child's mother or mother surrogate. Among the measuresof interest for the present report were scaled measures ofmarital disharmon y derived from the General Functioningscale of the McMaster Family Assessment Device (Byles etaI., 1988; Epstein et aI., 1983), of family dysfunction (DelVecchio et aI., 1979), and of stressful life events (Codding­ton, 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 TRFand a short form of the School Behav ior Inventory-Revised(SBI-R) (Bauermeister, 1990) from the child's homeroomteacher. All of the measures were administered and codedby trained lay interviewers.

In order to obtain a measure of impairment, the childpsychiatrist gave each child a score on the Children' s GlobalAssessment Scale (CGAS) (Bird et aI., 1987, 1990; Shafferet aI., 1983). Scores on the CGAS can range from 0 (severeimpairment) to 100 (superior functioning). In the validationof the CGAS with the data from Puerto Rico, a cutoff scoreof 61 was found to be the best discriminator to distinguishbetween children who exhibited definite maladjustment andothers (Bird et aI., 1987, 1990).

J. Am.Acad. Child Adolesc. Psychiatry, 31:3, May 1992

DIMENSIONS ATTENT IONAL- HYPERAC TIVITY SYNDROM ES

T A BL E I. Factor Loadings fo r the Teacher-Rated Descriptors ofADHD and Inattention Symptoms

Constantly movesbody or parts(hands, feet, etc.) (I ) 0.29 0.61

Can't sit still, restless, or hyper-active (2) O.I I 0.83

Easily distracts (3) 0.73 0.35Impulsive or acts without think-

ing (5) 0.22 0.74Difficulty following instruc-

tions (6) 0.73 0.31Can' t concentrate, can't pay at-

tention for long (7) 0.77 0.27Fails to fini sh things (8) 0.74 0.29Talks too much (10) O.I I 0.81Interrupts class ( I I) 0.17 0.84Stares blankly (12) 0.77 0.02Gets hurt a lot, accident prone

(14) 0.09 0.42Gets tired too much 0.45 0.4 1Lazy 0.76 0.30Confused or seems to be in a

fog 0.75 0.2 1Apathetic and lacks motivation 0.77 0.23Underactive, slow moving, or

lacks energy 0.76 0.18Shows lack of persistence 0.78 0.24

a Numbers in parentheses identify the corresponding DSM-lll-Rsymptom.

Cluster Analyses

Scores on the two scales were subsequently computed foreach of the 170 children in the second-stage sample whoeither met criteria for a DSM-lII diagnosis of ADDH (N =56) or ADDWO (N = 20), or who did not meet criteria forany DSM-III diagnosis (N = 94) . These scores were sub­jected to a Ward ' s cluster analysis (Everitt, 1980) to analyzethe way in which children in this sam ple clustered. Exa mina­tion of the cubic clustering criterion and cluster dendrogramssuggested that the children can be clas sified into either threeor five clusters. The three cluster solution lacked clea r clini­calor conceptual sense. The five cluster solution yieldedmore meaningful profi les that accounted for 88% of thevariance . These five clusters were used in subsequen t ana ly­ses.

The me an Inattention an d Hyper act ivity-Impulsi vi tyscores for the children in eac h cluster, as well as for thetotal sam ple of 6 14 children, are presented in Table 2. Thefirst cluster (Hyperactive) was characterized by high hyper­activity-impulsivi ty and moderately high inattent ion scores;by contrast, cluster 2 (Inattentive) had very high inattent ionbut very low hyperactivity-impul sivity scores, resemblin gthe DSM-III-R, UADD catego ry; cluster 3 (Inattentive -Hy­peractive) was characterized by high scores on both inatten­tion and hyperactivity-impulsivity, and the profile resembl esthe category of ADDH in DSM-III; cluster 4 (Normal) had

To construct a teacher rating scale of behaviors indicat iveof DSM-IlI-R ADHD and of ADDWOfUADD, a set of itemsthat described symptoms of these disorders were drawn fromthe TRF and the SBI-R. From these two instruments, a panelof two child psych iatrists and three psychologists independ­ently selected II items that best matched ADHD symptoms.In addit ion, six items descriptive of inattention/sluggishnessin the classroom were added to the pool (gets tired too much ,lazy, co nfused, apa theti c, un deract ive, and lacks persis­tence) . 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 factor analyzed using principal compo­nent s factor analysis with Yarimax rotation. Data from the614 children aged 6 through 16 years who part icipated inthe first stage of the epidemiological survey were used forthis analysis. Factors with eige nvalues above 1.0 were ex­tracted. To analyze the way in which children with clinica ldiagnoses of ADD and without any diagnosis clustered onthe basis of these factors, Ward ' s (1963) cluster analysiswas performed on the 170 subjects from the second stageof the survey that met the ADDH and ADDWO diagnosticcriteria, or who had no diagnosis. Finally, cluster differencesin sociodemographic, clinical, fami ly, school , and deve lop­mental variables were analyzed using univariate analyses ofvariance (AN OYAS) and chi-square tests. In view of thelarge number of statistica l tests, only results having a proba­bility value of p :s; 0.0 1 were considered statistically signifi­cant to reduce the likelih ood of type I error. Whenever theseanalyses were significa nt, Newman-Keuls pairwise contrastsor chi-square tests (p :s; 0.05) were used to analyze potentialgroup differences.

Results

Factor Analyses

The factor analysis of the 17 items selected yielded twofactors with eigen values above 1.0 (Table I). The y havebeen labeled as Inattent ion and Hyperactivity-Impulsivity,based on their item co mposition. Th ese two fac tors ac ­counted for 59.3% of the component variance. To examinethe stability of the factor structure obtained for the totalsam ple, the analyses were replicated on three age groups ofthe same sample: children aged 6 through 9 years (N =22 1), those 10 through 12 years (N = 162), and those 13through 16 years (N = 231) . The factor structure for eachof these age groups was almost identical to the one obtainedfor the total sample. Two factor scales were constructed byselecting the items with the highest loadings on the Inatten­tion (I I items) and the Hyperactivity-Impulsivity (6 items)factors. Cronbach's alpha coefficients and item-total correla­tions were computed for each scale. The results provideevidence for the internal reliability of the scales. Th e alphacoefficient for the Inattent ion scale was 0.93, with item­total correlations ranging from 0.51 to 0.77. Alph a for theHyperactivity-Impulsivity scale was 0.84, with item-t otalcorrelations ranging from 0.32 to 0.75.

Items"Inattention

Factor

Hyperactivity­Impulsivity

Factor

J. Am.Acad. Child Ado/esc. Psychiatry ,31:3, May 1992 425

BAUERMEISTER ET AL.

TABLE 2. Mean Inattention and Hyperactivity Scale Scores for the Total Community Sample and Five Clusters of Children with DSM-IIIDiagnoses of ADD or No Diagnoses

Total Cluster

Scale Sample H I IH N HA

N 614 15 15 42 36 62Inattention Scale

X 7.08 11.33 17.87 16.57 9.42 1.87SD 6.21 1.35 2.45 2.24 2.50 1.72

Hyperactivity ScaleX 2.54 8.47 .93 7.24 2.28 1.56SD 2.90 1.41 .80 2.10 2.04 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 samplemeans; and finally, cluster 5 (Highly Adapted) had scoreson both factors that were lower than the total sample mean.The means of the scales of Inattention and Hyperactivity ofthe five clusters were compared with the means of the totalfirst stage sample (N = 614). In these comparisons, thesubjects belonging to a given cluster were excluded fromthe computation of the total sample means. With the excep­tion of the Inattention and Hyperactivity-Impulsivity scoresin the Normal cluster, and the Hyperactivity-Impulsivityscore in the Inattentive cluster, the mean scores of each ofthe clusters were significantly different from the total samplemeans (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 (Table2). In order to determine if these two clusters could beaccurately discriminated on the basis of the type of inatten­tion symptoms rated by the teacher, a stepwise discriminantfunction 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 grouphad higher scores on the following items: underactive andslow moving, fails to finish things, apathetic and lacks moti­vation, stares blankly, can't concentrate, and lazy. The IHgroup had higher scores on: confused, gets tired too much,and show lacks of persistence. Thus, the I and the IH clusterscan be distinguished not only on the basis of their meanhyperactivity and impulsivity scores, but on the rating ofspecific inattention items by the teachers as well.

Relationship of the Clusters to Demographic Variables

Table 3 presents sex and socioeconomic (SES) data forthe five clusters. Because the survey sample was predomi­nantly of lower SES (Bird et al., 1988), Hollingshead classesI through IV were grouped together into a single categoryto 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 smallerproportion 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 ofchildren from the lower SES were also found in the IHcluster, relative to the Normal (N) and HA clusters. Nosignificant 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 resultswere aggregated into four major supraordinate categoriesfollowing the scheme reported by Bird et al. (1988). Thisserved to increase the expected cell frequencies in the chi­square tests. The four supraordinate diagnostic categorieswere: (1) attention deficit disorders, with and without hyper­activity; (2) affective disorders, consisting of major de­pressive disorder, dysthymic disorder, and cyclothymicdisorder; (3) anxiety disorders, including separation anxietydisorder, the phobias, overanxious disorder, obsessive-com­pulsive disorder, panic disorder, and avoidant disorder; and(4) conduct/oppositional disorder encompassing those twocategories. As indicated in Table 3, there were significantdifferences 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 differsignificantly on the percentage of ADD diagnoses received,but all three clusters had a significantly greater proportionof children with ADD diagnoses than the Nand HA groups.The HA cluster also had a significantly lower percentage ofchildren with the conduct/oppositional disorder diagnosis,whereas the remaining four clusters did not differ in thefrequency with which this disorder was diagnosed. Therewere no apparent differences among the clusters on theproportion of children with affective disorders, although theHand IHclusters seemed to have more children with anxietydisorders. However, significance testing was not possiblefor these two categories due to the small numbers of childrenin the various cells. This same limitation precluded a chi­square analysis for the breakdown between the ADDH andADDWO diagnostic categories. Approximately 73% of thechildren in the H cluster and 60% in the IH cluster receivedADDH diagnoses. The children in the I cluster were equallylikely 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, 3I: 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 ComparisonsVariable H IH N HA among Clusters

Demographic variablesSex (males)" 80.0 60.0 69.0 61.1 35.5 H, IH, N> HALower SEsa 73.3 21.4 43.9 22.9 24.6 H > I, IH, N, HA; IH > N, HA

Clinical statusADD 80.0 66.7 73.8 36.1 16.1 H, I, IH > N > HAConduct/oppositional

disorder 33.3 33.3 35.7 27.8 6.5 H, I, IH, N > HAXCGAS Score" 59.60 62.13 59.29 72.8 1 78.15 H, I, IH < N < HA

CBCL scalesAggressive" 66.80 66.60 70.09 63.69 62.50 IH > N, HADelinquen t" 63.73 63.67 67.14 62.50 59.98 IH > N, HAHyperac tive" 68.80 68.13 71.26 62.39 60.48 I, H, IH > N, HATotal problems" 66.20 67.00 70.29 6 1.31 60.05 IH > N, HA

School performanceGrade failure" 46.7 33.3 54.8 16.7 3.2 H, IH > N, HA; I, N > HA

TRFSocia l withdrawal" 61.27 76.60 70.62 63.44 58.44 I > IH > H, N, HA; N > HAUnpopular!' 63.73 62.07 67.10 59.3 1 57.32 IH> I, N, HA; H > N, HA; I > HAAnxious" 63.20 60.80 65.93 58.89 58.60 IH > I, N, HA; H > HAAggressiveb 65.73 56.60 68.57 57.19 56.60 H, IH > I, N, HASelf-destructi ve" 63.53 60.33 65.07 59.83 58.32 H, IH > N, HA; IH > ITotal problems" 66.60 63.20 71.76 57.6 1 50.79 IH > H, I > N > HA

Developmental variablesPregnancy comp lications" 40.0 21.4 71.8 44.4 48.4 IH > H, I, N, HALanguage development"

Slower or much slower 6.7 40.0 41.0 8.3 11.3 I, IH > H, N, HA

Note: With the exception of CGAS, CBCL, 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 Assessment Scale;

CBCL, Child Behavior Checklist.Comp arisons among clusters are the results of pairwise 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-square 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 distinctpattern that distinguishes the three " disorders" clusters (I,IH, H) from each other, even though they do differ from thenormal (N) and the highly adapted HA clusters.

Significant differences were obtai ned for the CGA Sscores, F(4 ,165) = 24.08. In pairwise comparisons, the H,I, and IH clusters had comparable CGAS scores, all of whichwere significantly (p ~ 0.05) lower (i.e., in the more impairedrange) than those of the Nand HA clusters.

Relationship of Clusters to Relevant Scales on the CBCL

Cluster similarities and differences on the Aggressive,Delinquent , Hyperactive, and Tot al Behavior Problem(TBP) scores of the CBCL were compared using ANOVAS.These CBCL scales were selected for analysis because theycontai n similar items for both genders and the two agegroupings (6 to 11; 12 to 16 years) under investigation.Following the method recommended for combining samplesof different sex and age in the same dimension (Achenbachand Edelbrock, 1986, p. 128), the raw scores on these scaleswere converted to T scores based on the norms for their sex

J.Am .Acad. Child Adolesc. Psychiatry,31:3, May 1992

and age. This procedure permits the analyses of T scorescombining children of more than one sex/age group on anal­ogous factors of the CBCL. Significant differences amongthe 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 comparisonsindicate that only the IH cluster obtained significantly higherscores on the Aggressive, Delinquent, and TBP scales thanthe Nand HA clusters (Table 3). Children classified in theH, I, and IH clusters obtained significantly higher scores onthe Hyperactive CBCL scale than those classified in the Nand HA clusters; nevertheless, the first three and the lattertwo did not differ significantly among themselves. This find­ing is not surprising since the CBCL Hyperactive scaleincludes 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 childrenwho had failed a grade was significantly greater in the Hand IH clusters than it was in the Nand HA clusters. The I

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and N clusters did not differ significantly on this proportionbut were significantly different from the HA cluster, whichhad the lowest rate of grade failure.

TRF T scores were computed for those scales that havecommon items in the same dimension for the age/sex groupsstudied followin g the method recommended by Achenbachand Edelbrock (1986, p. 128). Since the clusters were identi­fied based on teacher ratings of inattention and hyperactivi­ty-impul sivity items, it is expected that other teacher ratingsof variables that covary with the clustering criteria will alsorelate to the clusters. However, such analyses are useful todemonstrate the range of behavior problems associated withhigh 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 ofthe TRF; F(4,165) = 42.93,1 9.76,10.74,35.70,10.06, and81.74, respectively. Pairwise comparisons (Table 3) indi­cated that children in the I cluster had significantly higherscores on the Social Withdrawal scale than children in thelH cluster, who in tum , had significantly higher scores onthis scale than children in the other three clusters. Childrenin the IH group had significantly higher scores than childrenin the I, N, and HA clusters, on the Unpopular, Anxious,Aggressive, Self-Destructive, and TBP scales; they also hadsignificantly higher scores on the TBP scale than childrenin the H group. With the exception of the Social Withdrawalscale, the H group had significantly higher scores on theother TRF scales than did the N or HA clusters, and signifi­cantly higher scores on the Aggressive scale than childrenin the I cluster.

The five clusters differed significantly on the scores ob­tained in the Language, Memory, and Reading scales of therevised 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 didnot differ significantly on these measures but were rated aspresenting more difficultie s on these scales than the N orHA clusters. Children in the I cluster presented a signifi­cantly higher level of reading difficulties than those in theIH cluster.

Relationship of the Clusters to Early Developmental andFamily Related Variables

The examination of the possible relationship between theclusters and other measures was restricted to those variablesfor which some type of association could be anticipated onconceptual grounds. Table 3 includes those variables forwhich significant associations were found. Maternal reportsof pregnancy complications and of delays in language devel­opment were the only early developmental variables signifi­cantly related with the clusters extracted, X2 (4) = 13.09 and22.39, respectively. Approximately 72% of the mothers ofthe children in the IH cluster reported complications duringpregnancy. Pregnancy complications included those that areconsidered to be of salient importance by both obstetriciansand pediatricians (e.g., albuminuria, hypertension, first tri­mester bleeding, etc.). The proportion of pregnancy compli-

428

cations present in the IH cluster is significantly higher thanthat reported for the other clusters. The proporti on of moth­ers reporting that their children learned to speak and to uselanguage for communication later than other children wassignificantly greater in the I and lH clusters than in the otherthree groups. No significant differences were found amongthe clusters in relationship to the variables measuring perina­tal complications and the child's general health status.

Four famil y related variables were con sidered : sca ledmeasures of marital harmony, overall family dysfunctionand stressful life events, and a categorical measure relatedto single parenthood. ANOVAS were conducted for thescores on each of the three scaled measures, and no signifi­cant differences among the clusters (p < 0.05) could bedetected. Membership in the five clusters was not associated(X2

) with single parenthood.

Discussion

The goals of the present study were to examine whetherteacher ratings of items that match ADHD symptoms andother items related to inattention organize into single ormultiple dimensions of maladaptive behavior, and to explorethe possible existence of ADDWOIUADD as a separatediagnostic category. The factor analysis of teacher ratingsyielded 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-impulsivity 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 wereperformed for three age groups (6-9, 10-12, and 13-1 6years), a finding that supports the stability of the factorstructure obtained for the entire range (6-16 years). Thesefindings concur with those reported by other research(Bauermeister, 1992; Healey et aI., 1987; Lahey and Carl­son, 1991; Lahey et aI., 1988). The data do not provideempirical support to favor a unidimensional definition ofADHD, such as the one proposed in DSM-lll-R; in fact, thesymptoms of the disorder are organized into two relativelyindependent dimensions. The findings do support the DSM­Ill-R definition of UADD, since a number of children wereclassified into a cluster of symptoms that were found tobe 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 disorderwere symptoms of inattention and impulsi vity, but not hy­peractivity. The present findings, and those reported by theinvestigators cited (Bauermeister, 1992; Healey et al., 1987;Lahey and Carlson, 1991; Lahey et aI., 1988), demonstratethat items describing overt impulsivity do not load togetherwith the inattent ion factor but rather with the hyperactivity­impulsivity factor.

Cluster analysis was performed on the Inattention andHyperactivity-Impulsivity factor scores in order to examine

J. Am. Acad. Child Ado lesc. Psychiatry, 31:3, May 1992

the profiles of children who had been diagnosed in the sur­vey as ADDH, ADDWO, or normals. The children in theH, I, and IH clusters showed more clinical impairment thanthe N and HA groups. A considerable proportion of childrenin 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 «61) (Bird et aI., 1987; Bird et aI., 1988); had repeated agrade in school; and were rated by their teachers as pre­senting memory, language, and reading difficulties.

Although children in the three "clinical" clusters all meetsimilar criteria of maladjustment, they appear to present adifferent pattern of correlates that support their discriminantvalidity and have potential theoretical and clinical implica­tions. The present findings suggest that the Inattentive andInattentive-Hype ractive clusters represent two distinct syn­dromes consisting of children who appear to exhibit ADDHand ADDWOIUADD, respectively. The Inattentive-Hyper­active children are significantly more active and impulsive,have a higher rate of reported pregnancy complications intheir 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 problemsthan the Normal and the Highly Adapted groups. The Inat­tentive group was rated by teachers as more socially with­drawn than the other groups and as having more readingdifficulties 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 whichchildren classi fied as ADDW and ADDWO on the basis ofteacher 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 reported in theliterature (Barkley et aI., 1990; Biederman et aI., 1987; Hyndet aI., 1991; Munir et aI., 1987), ADDH children have beenfou nd to be more like ly to receive the codiagnosis ofconduct/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 proportionwas not significantly different from what it was in the Inat­tentive, Hyperactive, or Normal groups. This finding maybe explained by the extremely higher degree of comorbiditybetween the conduct/oppositional diagnoses and all otherdiagnoses reported in the survey and by the low prevalenceof pure conduct/oppositional disorders (Bird et al., 1988).The Inattentive-Hyperactive group, however, appears to dis­play a pattern of more aggressive and delinquent behaviorsat home and/or school.

Although the Inatt enti ve and Inattentive-Hyperact iveclusters have similar levels of deviance on inattention, theresults of the discriminant function analysis suggest that thetwo groups represent qualitatively different disorders. TheInattentive group presented a profile of higher ratings of

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DIMENSIONS ATIENTIONAL-HYPERACTIV ITY SYNDROMES

" underactivity or movin g slow ly, " " fai lure to finishthings," " apathy," " blank staring," " concentration prob­lems," and "laziness," and lower ratings on " confusion"and "getting tired too much." There is similarity betweenthese findings and those of Lah ey et al. (198 5, 1987 ),wherein ADDWO children are more sluggish and drowsythan ADDH children.

The Inattentive and Inattentive-Hyperactive clusters donot differ significantly among themselves, nor from the otherthree clusters, on the family risk factor measures (maritalharmony, overall fami ly dysfu nct ion , and stressful li feevents). Similar findings for ADDH and ADDWO groupsof children have been reported by Barkley et aI. (1990).The proportion of children with reported delays in languagedevelopment was significantly greater in the Inattentive andInatten tive-Hyperacti ve clu sters than in the other threegroups. These data are of particular interest in view of thefindings from other community-based samples that ADDHchildre n are more likely to be delayed in language andspeec h acquisition than normal children (Har tso ugh andLambert, 1985; Stewart et aI., 1966; Szatmari et aI., 1989).The data suggest that the ADDWOIUADD child may alsopresent a similar history. Furthermore, the findings suggestthat language delay is an important antecedent of inattentivebehaviors, since children in the pure Hyperacti ve cluster didnot present such delays.

Children in the Hyperactive cluster are characterized bymoderately high inattention scores and high hyperac tivityscores, and they also appear to exhibit ADDH. This groupof children, however, present a pattern of correlates that isdifferent from that of the Inattentive-Hyperactive children:it included the highest proportion of males and children oflower SES. The children in the Hyperactive cluster wererated by their teachers as less socially withdrawn than thosein the other two clinical clusters and were rated similarlyto the Inattentive-Hyperactive group on the other behaviorscales, with the exception of the total behavior problemscale. They were rated by their parents to be as hyperactiveas the children in the Inattentive and Inattentive-Hyperactiveclusters. Further research is needed to understand the clinicalsignificance of the Hyperactive group defined here, particu­larly when two other studies have also identified a lessclearly inatte ntive but hyperactive- impulsive group fromteacher ratings of ADHD symptoms. (Bauermeister, 1992;Newcorn et aI., 1989). It is conceivable that children of lowSES present a behavioral style of overactivity and impulsiv­ity in the classroom setting that is associated with theirsocialization experiences and parenting styles rather thanwith impaired attention.

Understandably, the level of agreement between the clini­cians' ADDH and ADDWO diagnoses and applicable clus­ter membership was not high, particularly for the ADDWOdiagnoses. The cluster analysis was based on teacher ratingsof inattention and hyperactivity-impulsivity symptoms inthe classroo m setting. The diagnoses, however, were basedon DSM-III symptoms elicited from the parents and childrenusing the DISC. Since DSM -1I1 symptoms for inattention,hyperactivity, and impulsivity do not cluster into dimensionsthat correspond to the three DSM-llI criteria, diagnosing

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children on the basis of these criter ia may result in relativelyimpure groups of ADDH and ADDWO (Barkley et al., 1990;Lahey et al., 1988). Furthermore, the clinicians were blindto the CBCL, TRF, or SBI-R scores, and thus had no infor­mation about ratings of a number of behaviors of interest inother situations.

The findings of the present study are the first to supportthe discriminant validity of the ADDWOIUADD diagnosisin a community sample. These findings respond to the mainpurpose of the study, namely, whether attentional deficits areunidimensional or multidimensional constructs and whetherADDWO/UADD exis ts as a se para te diagn osi s fro mADDH. Further research is now needed on the specificityofthe ADDWOIUADD diagnosis with respect to other diag­noses (Werry et al., 1987).

The issue could be raised of whether the cluster solutionchosen can be considered performance clusters and groupsof children that are quantitatively but not qualitat ively differ­ent. However, the pattern of cluster correlates for the devel­opment al variables studied and the different profiles ofinattention symptoms among the Inattentive and Inattentive­Hyperactive groups argue against this possibility. This is aHispanic sample, representative of the children in PuertoRico. The levels of psychopathology in this sample appearedto be different to those of mainland samples; similarly, thepattern s of psychop athology could also be different. Al­though several of the findings in this study are similar tothose reported for U.S. samples (Lahey and Carlson, 1991),the generalizability of these findings is an issue that canonly 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 precluded analyses of addi­tional measures of interest and limited the statistical powerto detect potential cluster differences. In addition, cognitivemeasures were not available on the children studied. Shouldsystematic differences in intellectual ability exi st acrossgroups, cognitive level could have contributed to the differ­ences found on other measures. Notwithstanding these limi­tations, there are implications from these findings for theconceptualization and definition of the attention deficit dis­orders in DSM-IV. First, these data, and those reported byother investigators (Bauermeister, 1992; Healey et al., 1987;Lahey and Carlson, 1991; Lahey et al., 1988) suggest thatfor children aged 6 through 16 years, a distinct bidimensio­nal entity exists. In this conceptualization, symptoms of bothinattention and of hyperactivity-impulsivity are necessaryfor a diagnosis to be present. This definition results in theclassification of a narrower but more clinically homoge­neous group of children who are both hyperacti ve and inat­tentive. In conceptualizing the disorders, DSM-IV will needto take into account age and developmental stages. Recentfindings from factor analysis of teacher ratings suggest thatfor children aged 4 and 5 years of age, ADHD symptomsappear to covary in a single dimension (Bauermeister, 1992).Second, the data suggest that an attention deficit syndromewithout symptoms of hyperactivity or impulsivity, similarto the DSM-III-R description of UADD, exists as a distinctbehavioral syndrome observable in the school setting. Un-

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deractivity, failure to finish things, apathy, blank staring,and drowsine ss appear to be some of the manifestations ofthis syndrome. These data, and the findings reported byLahey et a1. (1984, 1985, 1987, 1988), suggest that thistype of attention deficit should continue to be considered aseparate diagnostic category in DSM-IV. Finally, the findingthat children rated as moderately inattentive and hyperactive(the Hyperactive Cluster) present a distinct pattern of corre­lates raises questions about the possible existence of stillanother subtype. DSM-I V needs to develop a more explicitoperationalization of criteria as well as separate continuousmeasures of inattent ion and hyperactivity to assist in thediagnosis of possible ADD subtypes. Properl y normed con­tinuous measures of teacher or parent ratings of ADDH orADDWOIUADD symptoms can provide necessary clinicaland statistical means to assess deviant behaviors and symp­toms of development ally inappropriate inattention and hy­peractivity-impul sivity (Barkley, 1990).

ReferencesAchenbach, T . M. & Edel brock, C. (19 83), Manual f or the Child

Behavior 'Checklist and Revised Child Behavior Profi le. Qu eenCity, VT: Q ueen Ci ty Pr inte rs.

-- - - (1 986) , Man ual fo r the Teache r 's Rep ort Fo rm a ndTeacher Version of the Child Behavior Profile. Burlington , VT:University of Vermont.

Barkley, R. A. (1990), Attention Defi cit Hyperactivity Diso rder: AHandbook for Diagnosis and Treatment. New York: Gui lford.

-- Dupaul, G. J. & McMurray, M.B . ( 1990), Comprehensive evalu­ation of attentio n deficit disorder with and without hyperactivity asdefi ned by research cri teria. J. Consult . Clinical Psychol.• 58:775­789.

Bauermeister, J. (1990), Develop ment of multi va riate ass ess mentscales for Puerto Rican Children. Paper presented at the annualconvention of the America n Psychological Associa tio n, Ma ssac hu­setts.

- .- ( 1992) , Factor analyses of teacher ratin gs of atten tio n deficit ­hyperacti vity and op pos itional defiant symptoms in children agedfour through thirteen years. Journ al of Clinical Child Psychology,21:27-34.

Biederman, J., Mu nir, K. & Knee, D. (198 7), Conduct and opposi­tio nal disorder in clinica lly referred children with attention deficitdiso rder: a co ntro lled fam ily study . J. Am . Acad. Child Adolesc.Psychiatry, 26:724-727.

Bird , H., Canino , G., Ru bio-S tipec , M. & Ribera, J. (1987), Furthermeasures of the psychometric properties of the Childre n's Glob alAssessment Sca le (CGAS) . Arch. Gen. Psychiatry, 44 :82 1-824.

--- - Rubio-Stipec, M.. et al. (19 88), Estima tes of the prevalenceof chi ldhood maladj ustment in a community survey in Puerto Rico .Arch. Gen. Psychiatry , 45: 1120- 1126.

-- Yager, T . J., Staghezza, B., Gould, M. S ., Cani no, G . & Rubio­St ipec, M. (1990), Im pai rment in the epi demiological measurementof childhood psychopathology in the community . J. Am. Acad.Child Adolesc. Psychiatry, 29:796-803.

Byle s, J ., Byrne, C, Boyle, M. & Offord, D. (1988), Ontario ChildHealth Study: reliability and val idity of the genera l func tion ingsubseaIe of the McM aster famil y assessment dev ice . Fam. Process ,27:97- 104.

Can ino, G., Bird. H., Rubio-St ipec, M., Woodbury, M., Ribera, J .,Huertas, S. & Se sman, M. (1987) , Reliab ility of chi ld diagnosisin a Hispanic sample. J. Am. Acad. Child Adolesc. Psychiatry,26 :560-565 .

Coddingto n, R. D. (1972), Th e significance of life eve nts as etiologicfactor s in the diseases of children. II. A study of a norm al popula­tion. J. Psychosom. Res., 16:205- 213.

Cos tello, A. J. , Edelbrock, c, Du lcan, M. K., Kalas, R. & Klaric, S.(1987) , Diagnostic Interview Schedul e for Children (DISC). West-

J. Am.Acad. Child Adolesc. Psychiatry, 31:3,May 1992

ern Psychi atric Institute and Clinic, Schoo l of Medi cine, Universityof Pitt sburgh.

Del Vecchio, M. J., Smi lkstein , G., Goo d, B. J. , Shaffer, T. & Arons,T . (197 9), The family Apgar index : a study of cons truc t validity.J. Fam. Pract., 8:577-582.

Edelbrock, C, Cos tello , A. J. & Kess ler, D. (198 4), Em pirical corrobo­rat ion of the attent ion deficit di sorder. J. Am. Acad. Child Adolesc.Psychiatry, 23:285-290.

Ep stei n, N. B., Baldwin , L. M. & Bishop, D. S. (1983), The McMasterFamily Assessment Device. J. Marita l Fam. Ther., 9:171- 180.

Eve ritt, B. S. (1980), Cluster Analysis , 2nd Edi tion. Lond on: Heine­mann .

Hart, E. A., Lahey, B. B., Hem , K., Hyno, G. W., Frick, P. J. &Hanson, K. (1990), Dimension s and types of ADD: Two replica­tions . Manuscript submitted for publication.

Hartsough, C. S. & Lambert, N. M. (1985), Medical factors in hyperac­tive and normal children : pren atal , developmental, and health his­tory findings. Am. J. Orthopsychiatry, 55:190-210.

Healy , J. M., Halperin, J. M., Newcom , J. et al. (1987), The factorstruc ture of ADD items in DSM-llI-R. Paper presented at the annualmeetin g of the American Academy of Ch ild and Ad ole scent Psych i­atry , Washin gton , DC.

Hyn d, G., Lor ys-Ve rnon, A ., Semrud -C likem an, M ., Nieves, N.,Huettn er , M. & Lahey, B. B. (199 1), Attention deficit disorderwithout hyperacti vity (ADD/WO) : a distin ct behavioral and neuro­cog nitive syndrome. J. Child Neurol., 6:37-43

King, C. & Youn g, R. D. (19 82), Attentional deficits with and withouthyperactiv ity: teacher and peer perceptions. J. Abnonn. Child Psy­chol., 10:483-495.

Lahey, B. B. & Carlson, C. L. (1991 ), Va lidity of the diagnosticcategory of attention deficit disorder without hyperac tiv ity: a reviewof the litera ture. J. Learn Disabil., 24 :110-1 20.

-- Schaughency , E. A ., Strauss, C. C. & Frame , C. L. (19 84), Areatten tion defi cit disor der s with and without hyperact ivity similar

J.Am.A cad. Child Adolesc. Psy chiatry, 31:3, May 1992

DIMENSIONS ATIENTIONAL- HYPERACTIVITY SYNDROMES

or dissi milar disor ders? J. Am. Acad. Child Adolesc. Psychiatry,23 :302-309.

-- --Frame, E. L. & Straus s, C. C. (1985 ), Teacher ratings ofatte ntion probl ems in childre n experime ntally classified as ex hib­iting atten tion deficit disor ders with and without hyperactivity . J.Am. Acad. Child Adolesc. Psychiatry, 24 :613-6 16.

----Hynd , G. W., Carlson, C. L. & Nieves, N. ( 1987) , Atte ntio ndeficit disorder wit h and without hyperactivity: co mpa rison of be­havioral characteristics of clinic-referred chil dre n. J. Am . Acad.Child Adolesc. Psychia try, 26:718-723.

-- Pelh am , W. E., Schaughency , E. A. et al. (1988), Dimen sionsand types of atte ntion deficit disorder. J. Am . Acad. Child Adolesc.Psychiatry, 27:330-335 .

Mun ir, K., Biederm an, J. & Knee, D . (1987), Psychi atric comorbidi tyin patients with atten tion deficit disorder: a controlled study . J. Am.Acad. Child Adolesc. Psychiatry, 26:844-848.

Newcom, 1., Halperin, 1. M., Healy , J. et al. (1989) , Are ADDHand ADHD the same or different? 1. Am. Acad. Child Adolesc.Psychiatry, 285:734-738.

Shaffe r, D., Gould, M. S., Brasic, 1., Ambrosini, P. , Bird , H. R. &Aluwa hlia, S. (1983), A children 's glo bal assessment sca le (CG AS) .Arch. Gen . Psychiatry, 40 :1228-1 231.

Steward, M. A ., Pitts, F. N., Cra ig, A. G. & Diernf, W. (1966), Thehyperactive chi ld syndrome. Am. 1. Orthopsychiatry, 36:861-867 .

Sza tma ri, P., Offord, D. R. & Boy le, M. H. (1989), Correlates, assoc i­ated imp airment and patterns of service utilization of childre n wit hattent ion deficit disord ers: findings fro m the Ontario chi ld healthstudy. J. Child PsychoI. Psychiatry , 30:205-2 17.

Ward, J. (196 3), Hierarchical grou ping to op timize an objective func­tion. J. Am . Stat. Assoc., 58:236--244.

Werry, J. S., Reeves, J. C. & Elkind , G. S. (1987), Atten tion deficit,conduct oppositional, and anxiety disord ers in chi ldre n: I. A rev iewof research on differentiat ing cha racteri stics. J. Am . Acad. ChildAdolesc. Psychiat., 26 :133- 143.

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