Impact of Comorbid Oppositional or Conduct Problems on Attention-Deficit Hyperactivity Disorder

Impact of Comorbid Oppositional or Conduct Problems on Attention-Deficit Hyperactivity Disorder MICHAEL KUHNE, M.A., RUSSELL SCHACHAR, M.D ., AND ROSEMARYTANNOCK, PH.D .

ABSTRACT ObJective: To investigate whether the presence of comorbid oppositional defiant disorder (ODD) or conduct disorder (CD) alters the correlates of attent ion-deficit hyperactivity disorder (AOHO). Method: Three groups of children (33 ·pure" AOHO, 46 AOHO+OOO, and 12 AOHO+CO) were compared on measures of AOHO, aggression, anxiety, parental psychopathology, self-esteem, school, and social-emotional functioning . Results: Findings indicated that the presence of comorbid oppositional or conduct problems in children with AOHO altered the correlates of AOHO across a number of areas , including greater AOHO symptom severity and social dysfunct ion. Nevertheless, some correlates were more closely linked with the comorbid cond ition of AOHO+CO (e.g., higher aggression, anxiety, and maternal pathology, as well as decreased self-esteem), while others appeared more closely linked with AOHO+OOO (e.g., social withdrawal, elevated academic achievement paired with higher perceived scholastic competence). Conclusions: Findings support the distinctive profiles of the disruptive behavior disorder groups and emphasize the deleterious effects on the quality of life experienced by the comorb id conditions. The need for syndrome-specific interventions is stressed . J. Am. Acad. Child

Ado/esc. Psychiatry. 1997, 36(12):1715-1725. Key Words: attention-deficit hyperactivity disorder, comorbidity, oppositional defiant disorder, conduct disorder, definition.

The high degree of overlap among the disruptive behavior disorders (DBDs) has resulted in considerable debate about their distinctive properties. Oppositional defiant disorder (ODD), for example, has been found to coexist in as many as 35% of children with attentiondeficit hyperactivity disorder (ADHD) (Bird er al., 1988). Similarly, in Biederman and colleagues' review (1991) of 29 studies including referred and nonreferred samples, it was concluded that ADHD and conduct disorder (CD) co-occur in 30% to 50% of cases. In a Accepted May 23 . 1997. Drs. Tannock and Schachar arr with the Child Psychiatry Research Unit. Department of Child and Adolescent Psychiatry. Hospital for Sick Children, Toronto. Mr. Kuhneis a doctoral candidat« at the OntarioInstitute for Studies in EducationlUnilJn'1ity ofToronto; hecondumd this research duringhis inu rnship in Psychiatry Research at the Hospital for Sick Children under the supervision ofDr. Tannock. This research wassupported by grants from the Medical&search Councilof Canada and the Ontario Menta] Health Foundation (awarded to Drs. Schachar. Tannock, and Cunningham). The authors thank Penny Corkum fo r her assistanc« with datil management. Reprin«request: to Dr. Tannock. Department ofPsychiatry Rrsearch. Hospital for Sick Children, 555 Univmity Avenue. Toronto. Ontario. Canada M5G lX8. 0890-8567/97/3612-171 5/$0.300/0<01997 by the American Academy of Ch ild and Adolescent Psychiatry.

general population study by Cohen et al. (1993), 60% of the children with CD diagnoses had comorbid ODD and 47% of the children with ODD had comorbid CD. Studies of referred samples have reported even higher rates of comorbidity (e.g., Schachar and Wachsmuth, 1990). Establishing the distinction between ODD and CD, however, has often been less than clear, leading some to question the utility of maintaining these separately defined disorders (e.g., Anderson et al., 1987; Werry et al., 1987). It has been suggested, for example, that ODD may be more accurately viewed as a milder form of CD (Schachar and Wachsmuth, 1990). The limited research comparing the statistical covariation among symptoms of ODD and CD suggests that while these disorders are reasonably distinct from one another (as displayed in the way they group by symptomatology), they also tend to overlap, particularly on variables of aggression such as fighting and cruelty to animals (Lahey et al., 1992). As such , children meeting CD criteria often meet ODD criteria as in Frick and coworkers' study (1991) of clinic-referred children, in which 96% of the youths with CD also met criteria for ODD based on the DSM-III-R.

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While the identification of correlates (e.g., etiological, developmental, psychosocial outcome variables) cannot explain causation, the degree to which correlates in ODD and CD differ argues for their existence as separate clinical entities. Conversely, the degree to which these disorders fail to differ on their respective correlates argues for their commonality and/or shared expression or disposition. In a study by Schachar and Wachsmuth (1990), parental psychopathology did not differ significantly among ODD and CD groups, but both groups had increased paternal diagnoses compared with normal controls. Conversely, an increased prevalence of antisocial personality disorder in the biological parents of boys with CD compared with boys with ODD was found by Frick et al. (1992) . Parents of boys with ODD, on the other hand, were more likely than the clinic control group (44% of whom had ADHD and 44% of whom had a DSM-III-R anxiety disorder) to have antisocial personality disorder. Substance abuse has also been found to be more common among parents of youths with CD compared with youths with ODD or children with neither diagnosis (Faraone et al., 1991, 1992). With regard to social functioning, Schachar and Wachsmuth (1990) found that while ODD and CO children both had greater difficulty with peer and sibling relationships than the clinic control group, the ODD and CD groups did not differ from one another. The CD group was, however, rated by clinicians as characterizing a lack of affectional bonds to a greater degree than the ODD and clinic control groups. Reeves et at. (1987) also found CD and ODD to be very similar in their study of 105 children with either anxiety, ADHD, CD, or ODD and noted that ODD and CD seldom occurred in the absence of ADHD. In contrast, a comparison of ODD and CD adolescents by Rey et al. (1988) found that ODD adolescents were more socially competent at the time of referral than CD adolescents. Comorbid internalizing disorders are commonly found in CD/ODD adolescents, with estimates from the general population as high as 53% for comorbid anxiety disorders and 17.6% for comorbid depressive disorders (Bird et al., 1993). Few differences, however, appear to exist between ODD and CD, as demonstrated by Rey et al. (1988). Adolescents with CD were, however, rated significantly higher on the Externalizing 1716

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and Total Behavior Problems scales than adolescents with ODD. Similarly, in Soltys and coworkers' study (1992) of child psychiatric inpatients, CD and ODD children were found to be similar across all examined domains including anxiety and self-concept. Determining the degree to which ODD and CD are similar or different has important implications with regard to the conceptualization of their respective diagnostic categories. If ODD and CD share similar correlates, the utility in maintaining their categorical distinctiveness may be lost. If, as some research has shown, ODD and CD display correlational overlap with differences of increased pathology in CD groups being attributable to level of symptom severity (i.e., a linear dose response), a classification model reflecting a continuum of pathology (perhaps developmental in nature) may be appropriate. If, however, ODD and CD fail to share similar correlates and thereby display a difference in both kind and degree, then the association between these disorders is lost and they should be categorized as different disorders. Unfortunately, the individual effects that these conduct disturbance disorders have on ADHD remains unclear because of the lack of a systematic approach in cont rolling for comorbidity in past studies. Methodological inconsistencies such as failing to distinguish AoHD from conduct problems or grouping ODD and CD within a generic category of "conduct problems" have often resulted in obscured findings leading to deceptive conclusions. Thus, many previously found effects attributed to ADHD may, in fact, be more accurately reflected in the presence of ODD or CD. For example, while families of children with ADHD have been found to display higher levels of controlling, negative, and less responsive behaviors than parents of nonADHD children (Beferaand Barkley, 1985), it has since been suggested that these negative parent-child interactions may be more a function of conduct problems and aggression than of the core symptoms of ADHD itself (Taylor et al., 1986). Similarly, while earlier studies indicated higher rates of marital distress and separation in families with ADHo children (Cohen and Minde, 1983), more recent evidence suggests that marital discord is actually more related to conduct problems than to the primary symptoms of ADHD (Loeber, 1990). Social variables such as solo parenting, parental separations, parental psychopathology, and lower socioeconomic status have all been found to be more strongly

AM . ACAD. C H I LD AD OLES C . PS YC H IAT RY, 36 :1 2 . DE CEMBER 1997

OPPOSITIONAL/CONDUCT DISORDER WITH ADHD

associated with CD than with ADHD (Hinshaw, 1987). Finally, studies examining parental pathology have found that parental antisocial personality disorder and substance abuse are associated with CD in children (who often have accompanying ADHD) and not with ADHD itself (Faraone et al., 1991; Lahey et al., 1988). In addition to family variables, studies comparing children who have ADHD with comorbid conduct problems versus children with ADHD alone have found significantly higher levels of pathology in the comorbid group across a variety of outcome measures. Child variables that have been associated with the additional presence of conduct problems have included increased aggression and delinquency (Loney et al., 1981), social problems (Reeves et al., 1987), and academic underachievement (e.g., Faraone et al., 1991). The purpose of the current study was to investigate whether the presence of comorbid ODD or CD would alter the correlates of ADHD. It was predicted that ADHD children with conduct problem disorders (i.e., ODD or CD) would fare worse with regard to parental psychopathology, social functioning, internalizing disorders, and measures of self-concept compared with ADHD children without any identified comorbidity. While findings on the distinction of ODD and CD are less consistent, we would expect ADHD children with comorbid CD to experience difficulty in the aforementioned domains above and beyond that experienced by ADHD+ODD children and in accordance with their hierarchical symptom severity. METHOD Subjects The current study examined baseline data from 91 children with ADHD and their families who participated in a treatment study involving stimulant medication and parent training (Schachar et al., 1997). Children included in the treatment study were between 5 and 12 years of age, were willing to participate in a randomized clinical trial, and had pervasive ADHD diagnosed through clinical diagnostic interviews as well as parent and teacher interviews (described below). Exclusionary criteria included a Full Scale IQ of less than 80, evidence of a neurological disorder (e.g., epilepsy), attendance at a full-time residential or day treatment program, previous treatment with medication for ADHD, a chronic or serious medical problem (e.g., diabetes), or a history of psychosis.

Diagnostic and Behavioral Measures Diagnosis of ADHD and any other concurrent disorders were based on the following measures: (1) a semistructured clinical diagnostic interview administered to the child's parents by an inter-

viewer (with clinical experience) trained to virtually 100% interrater reliability with child psychiatrist Dr. Schachar, (2) a semistructured clinical diagnostic interview conducted by telephone with the child's current classroom teacher, and (3) an assessment of the child. The Parent Interview for Child Symptoms (PICS) (Schachar and Wachsmuth, 1989) is a semistructured interview that probes for ADHD, ODD, and CD symptoms, among others. Teachers were interviewed by telephone using the Teacher Telephone Interview (TTl) which, similar to the PICS interview, examines ADHD, ODD, and CD symptoms in detail and screens for other disorders (e.g., overanxious disorder). The PICS and TTl ask the informant for detailed descriptions of the child's behavior in the home and school setting, respectively, leaving the clinician the decision of rating the behavior on a 4-point scale of severity and frequency. Both measures have been described in several previous publications and have demonstrated high inrerrater reliability and convergent validity (Schachar et aI., 1995). The child assessment included a screen for developmental disability (i.e., intellectual retardation). Inclusion within the study required a minimum estimated Full Scale IQ of 80 (short WISC-R using Block Design and Vocabulary subtesrs).

Diagnostic Groups Children with ADHD were assigned to one of three groups based on the presence/absence of diagnostic criteria as defined by the DSM-Ill-R. Criteria could be met through parent (as reponed on the PICS) or teacher (as reponed on the TTl) source or through both. The following groups were formed: (1) a "pure" ADHD group of children (n = 33) who had no comorbid ODD or CD (ADHD); (2) an ADHD group (n = 46) with co-occurring ODD (ADHD+ ODD); and (3) an ADHD group (n = 12) with co-occurring CD (ADHD+CD). By definition, ADHD children with both ODD and CD were classifiedas having ADHD+CD.

Child Measures and Variables Parent and teacher versions of the Ontario Child Health Study scales (OCHS) (Boyle et al., 1987, 1993) provided information on home and school functioning. In addition, parents completed the Family and Household Record (Boyle et al., 1987), which includes information on parent and child characteristics as well as family functioning. The following items as derived from both parent and teacher interviews were used as indicators of aggression: "initiates fights," "serious physical violence towards others," "spiteful or vindictive," and "bullies, threatens or intimidates." Aggression was coded as present if a child's parent (PICS) or teacher (TTl) reported moderate or pronounced levelsof aggression. Parent-reported and child self-reponed measures were used to measure anxiety. Anxiety was coded as present if a child's parent (PICS) reponed symptoms were consistent with the DSM-lII-R criteria for overanxious or separation anxiety. Self-reponed anxiety was measured through the use of the Revised Children's Manifest Anxiety Scale (RCMAS) (Reynolds and Richmond, 1985) and coded as present if the child scored at least 1 SD above the mean for age and gender as indicated by a Total Anxiety T score of ~60 as well as a "Lie scale" T score :513. Questions were read aloud to children so as not to introduce reading ability as a confound. Adequate internal consistency and construct validity (Paget and Reynolds, 1984; Reynolds and Richmond, 1985) as well as evidence of predictive validity (Ialongo et aI., 1995) have been reported for the RCMAS.

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TABLE 1 Description of Subjects ADHD = 33)

ADHD+ODD (n = 46)

ADHD+CD (n = 12)

36.3 28/5 8.4 (1.6) 107.2 (15.9)

50.5 34/12 8.2 (1.6) 110.5 (15.0)

13.2 12/0 8.6 (1.6) 103.7 (12.3)

Severity of ADHD PICS ADHD symptoms

9.1 (2.3)

11.9 (2.6)

Aggression Parent-rated Aggression Index"

0.1 (0.3) 0.2 (0.5)

Measures Proportion (%) of total sample Sex (M/F) Age (years) Estimated IQ (WISC -R est. FSIQ)

Teacher-rated Aggression Index" Anxiety Parent-rated b Child-rated' Parent- or child-rated

(n

F Value

Post Hoc Comparisons

(2.4)

12.6"

ADHD+ODD, ADHD+CD >ADHD

0.4 (0.5)

1.6 (1.4)

20.5"

0.5 (0.7)

1.3 (1.3)

9.9"

ADHD+CD > ADHD, ADHD+ODD ADHD+CD > ADHD, ADHD+ODD

n.s

9.1 12.1

26.1 17.4

50.0 50.0

8.8' 8.3'

21.2

41.3

91.7

18.1"

Proportions Test ADHD+CD > ADHD ADHD+CD > ADHD, ADHD+ODD ADHD+CD > ADHD, ADHD+ODD

Note: Except where otherwise indicated, values represent mean (standard deviation). ADHD = attention-deficit hyperactivity disorder; ODD = oppositional defiant disorder; CD = conduct disorder; FSIQ = Full Scale IQ; PICS = Parent Interview for Child Symptoms. "Mean of the number of aggression variables in which children were rated with 2's or 3's (i.e., moderate or severe ratings of symptoms). b Proportion of children rated by parents as experiencing anxiety (overanxious ~4 or separation anxiety ~3). "Proportion of children with self-reported anxiety on Revised Children's Manifest Anxiety Scale (Total Anxiety ~60 and Lie ~13) . 'p s .05; "r s .01.

Academic achievement was assessed using the Wide Range Achievement Test-Revised (WRAT-R) (Jastak and Wilkinson, 1987). The presence of a learning disability was defined by a score below 1.5 SD on any of the three subresrs of the WRAT-R (i.e., Reading, Spelling, or Arithmetic). An IQ-achievement discrepancy formula, therefore, was not adopted and is consistent with research demonstrating that IQ does not effectively serve to differentiate between dyslexics and poor readers with consistent IQ scores (e.g., Siegel, 1992). Finally, an Achievement Index was calculated and comprised the mean WRAT-R standard scores of Reading, Spelling, and Arithmetic. Two altruistic indices that were derived from the OCHS parent , teacher, and family and household forms consisted of those items involving helping or supporting others . The first index was labeled Emotionally Supportive and comprised four questions including praising less able children's work , showing sympathy toward mistakes, comforting someone upset, and clapping or smiling when someone does well. The second index was labeled Practical Helping/ Sharing and comprised seven items such as voluntarily sharing and helping. Finally, children's engagement in extracurricular and leisure activities was tapped through the use of several items on the parent OCHS questionnaire. Children's self-esteem (or self-perception of their own competence within several areas) was measured using the Self-Perception Profile for Children (Harter, 1985). Subjects rate themselves on 36 items, which load on the following domain -specific subscales : Scholastic Competence, Social Acceptance, Athletic Competence, Physical Appearance, Behavioral Conduct, and Global Self-Worth.

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Parent Measures and Variables Evidence for parental psychopathology was gathered through the use of the Symptom CheckJist-90-R (Derogaris, 1983). There are nine derived subscales of psychiatric symptomatology (e.g., interpersonal sensitivity, anxiety, depression) and three global symptom scores. Only mothers returned an adequate number of questionnaires (ADHD 79%, ADHD+ODD 89%, and ADHD+CD 92%). Fathers returned fewer than 50% of questionnaires across all groups and were not analyzed.

Analyses Contingency table analyses were performed on all dependent variables involving categorical data. Significant findings were followed up using dual-proportions testing for group contrasts. Variablesconstituting continuous data were compared across groups using oneway analysis of variance. Post hoc comparisons were performed on significant findings using the Tukey B test with a p < .05. All significant Pearson X2 values, F values, and degrees of freedom are reported in the tables.

RESULTS

Table 1 displays the descriptive characteristics of subjects including resultant group sizes and gender distributions. as well as age, IQ, severity of ADHD, level of aggression, and comorbid anxiety group comparisons.

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OPPOSITIONAL/CONDUCT DISORDER WITH ADHD

Half of the total sample of ADHD children had comorbid 000. In addition, of the ADHO children with comorbid CO (13.2% of the total sample), 11 (92%) of the 12 children also met ODD criteria. The proportion of ADHD children with co-occurring CD and/or ODD children (i.e., 64%) in the current study is similar to that of other studies (Biederman et al. [1987] reported 64% and Bird et al. [1988] reported 57%). While the gender distribution was uneven in all groups (i.e., consisting primarily of boys), it was most pronounced in the ADHD+CD group, in which only boys were present. No age or estimated IQ differences were found acrossgroups. Severity of ADHD, level of aggression, and level of anxiety were computed across groups. Severity of ADHD was based on the number of symptoms according to the diagnostic criterion (PICS and TTl, respectively). Both ADHD+ODD and ADHD+CD children displayed a higher number of ADHD symptoms (indicative of severity of ADHD) on the PIeS than the "pure" ADHD group (Table I). A similar trend was noted for symptom ratings on the TTl but failed to elicit significant results. Comorbid aggression and anxiety are also displayed in Table 1. Indicators of aggression were compiled into

an Aggression Index constituting the mean scores of aggression-related items. AOHD+CO children displayed consistently higher levels of aggression, reflected in the aggression indices for both parent and teacher. Group comparisons on anxiety indicate that ADHD+ CD children experience higher rates of anxiety (as represented by parent and/or child ratings) than the ADHD or ADHD+ODD children. The results of group comparisons on academic achievement are presented in Table 2. Of importance was the finding that on the Achievement Index, ADHD+ODD children performed significantly better than ADHD children. The ADHD+CD group's score was very similar to the ADHD group's score but failed to differ significantly from the ADHD+ODD children's score, possibly because of a lack of power. A definitive trend was observed as the ADHD+ODD children outperformed the other groups across all three subject areas. ADHD+ODD children performed significantly better than ADHD children in arithmetic. Although an analysis of variance found a significant difference between groups in reading ability and a marginally significant difference in spelling, post hoc comparisons yielded no significant group differences. Similarly, X2

TABLE 2 Academic Achievement and Self-Perceptions of Competence AOHO

Academic achievement Reading (WRAT-R SS) Spelling (WRAT-R SS) Arithmetic (WRAT-R SS) Achievement Index" Proportion of LO presence'< Student is in special education"

AOHO+OOO

F Value df= (2,88)

Post Hoc Comparisons (Tukey B)

3.8" 2.7' 6.5'" 4.3" 6.9" 7.5"

AOHO+OOO > AOHO AOHD+ODO > ADHD

(SO)

Mean

(SO)

Mean

(SO)

82.5 81.1 81.8 81.8 66.7 63.0

(17.0) (14.1) (16.2) (13.8)

91.7 87 .3 94 .5 91.1 39.1 30 .8

(21.3) (18.8) (15.1) (16.5)

77.3 76 .3 91.8 81.8 66 .7 58.3

(15.8) (11.6) (15.9) (13.1)

(3.8) (3.5)

19.2 10.9

(4.2) (3.4)

4.3" 4.6"

(4.2) (3.6) (4.9) (3.7)

16.9 13.5 13.4 16.2

(5.4) (4.9) (4.4) (6.0)

2.6' 3.7"

Children's self-perceptions of comperence (Haner scales)" (4.8) Athletic total 16.8 19.6 Behavior total 14.5 (5.0) 14.9 Physical total Scholastic total Social toral Global total

AOHO+CO

Mean

18.8 14.2 17.7 18.6

(4.5) (5.1) (4.5) (4.1)

19.4 16.1 16.3 19.0

Note: ADHD = arrenrion-deficit hyperactivity disorder; ODD = oppositional defiant disorder; CD Range Achievement Test-Revised; SS = standard score; LD = learning disability. a Mean SS of Reading, Spelling, and Arithmetic. b Defined as SS ~ 78 in Reading, Spelling, or Arithmetic, c Chi-square analyses. d Mean summed scores reponed (i.e., sum of six items on each subscale), , p s . 1; ") s .05; "'p ~ .01.

J.

AM . ACAD. CHILD ADOLESC. PSYCHIATRY. 36: 12. DE CEMBER 1997

AOHD > AOHO+ODO AOHD+OOO > AOHO AOHD, AOHD+ODD > AOHD+CO

AOHO > AOHO+CO

= conduct disorder; WRAT-R = Wide

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analyses of the proportion of learning disability presence across groups was significant, but follow-up proportions testing did not elicit significant differences. The proportion of ADHD students receiving special education was higher than that of ADHD+ODD students. Overall, the proportions of students receiving special education appeared to be consistent with the proportions of learning-disabled students across groups. There were no significant differences across groups in children's global self-perception of their own competence (i.e., self-esteem) (Table 2). ADHD+ODD children, however, did display elevated levels in their self-perceived athletic abilities compared with the ADHD group and demonstrated a trend toward higher scholastic esteem compared with the other groups. ADHD+CD children, on the other hand, displayed depressed levels of self-perceived competence in the areas of behavior and social functioning and, in general, demonstrated a pattern toward having a lower selfperception, with the exception of their self-perceived athletic abilities , which were similar to those of ADHD+ODD children . Inspection of the means indicates that ADHD+CD children's perception of their behavior falls within the clinical range (i.e., < 1 SD). Table 3 displays the variables as th ey relate to the child's social functioning. Included within this table is the child's engagement in extracurricular and leisure activities as well as home and family relations/effects. Findings within the social realm generally suggest greater adjustment difficulties in ADHD+ODD and ADHD+CD children than ADHD children. While the comorbid groups displayed relatively similar problems in many social areas, parental ratings of a child's peer relationships elicited a pattern in which, although not significant, ADHD+ODD children's social functioning was often rated to be even poorer than ADHD+CD children. For example, more ADHD +ODD children were rated to "do things less with other kids, " "have none or just one close friend ," and to have a "less enjoyable life" than either ADHD or ADHD+CD children. ADHD+CD children performed fewer extracurricular and leisure activities in general and were noted to miss more school and read significantly less than the other groups. Neither of the altruistic indexes displayed significant differences across groups. Self-ratings of maternal psychopathology (Table 4) demonstrated that mothers of ADHD+CD children

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rated themselves as significantly higher on the Global Severity Index and the Positive Symptom Total than mothers of ADHD children. This significant difference did not appear on the Positive Symptom Distress Index, although a similar trend was noted. At a symptom-specific level, the reports of ADHD+CD children's mothers indicated elevated levels of psychopathology in the areas of interpersonal sensitivity, anxiety, and hostility compared with ADHD children's mothers and elevated levels of paranoid ideation and psychoticism compared with both ADHD and ADHD+ODD children's mothers. While ADHD and ADHD+ODD mothers' ratings of psychopathological symptoms fell within 1 SO on all domains and indices , the majority of maternal ratings of ADHD+CD children fell above 1 SO from the mean (i.e., T scores >60). Maternal ratings of the ADHD+ODD children served as an intermediate group between ADHD and ADHD+CD on all domains with the exception of paranoid ideation, which was similar to ratings made by ADHD children's mothers. DISCUSSION

The comorbid conditions of ODD or CD appeared to exert a similar influence on ADHD correlates across a number of areas. Some correlates, however, were more closely linked with the comorbid condition of CD, resulting in a pattern consistent with the conceptualization of ODD as being a milder form of CD. There were, however, exceptions to this rule, suggesting that the notion that CD-associated difficulties are linearly related to ODD may be too simplistic. The increased social dysfunction evident in both comorbid conditions as well as the associated deleterious effects on family functioning suggest that conduct disturbance within children who have ADHD has a major effect on their ability to interact appropriately with others. In the current sample, children with ADHD+ODD appeared to be more often socially isolated (as indicated by a nonsignificant trend). Perhaps this , paired with their oppositional behavior, helps to explain why parents of children with ODD are more likely to use child mental health services than parents of other children with DBDs (Cohen et al., 1991). The ADHD+ODD group's relatively high level of academic achievement (with their mean Achievement Index score falling within the average range) compared

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OPPOSITIONAL/CONDUCT DISORDER WITH ADHD

TABLE 3 Social Functioning

Parent ratings Irritable or fighting with friends "a lot " Doing things less with other kids "a lot" Child's life has become "a lot" less enjoyable Child has none or just one close friend Child has not gotten along well with other kids such as friends or classmates" Caregiver'has seen someone from school re emotional or behavioral problems" Child has seen a psychiatrist, psychologist, or social worker for emotional or behavioral problems" Having "a lot" of trouble getting along with reachers" Missed school "a lot" Leisure activities Child took lessons in music, dance, art, or another nonsport activity" Child attended group or club meetings (e.g., Cubs, Brownies) at least once/week" Reads books or magazines for fun Effects on/relation to the home and family Child has "a lot" of trouble getting along with his/her parents Child's behavior has made it difficult for caregiver to taking him/her out in public" Caregiver has changed or forgone holidays because child's behavior is difficult to manage" Caregiver and spouse have often quarreled about child's behavior" Caregiver has often worried about child's chance for doing well in the future" Child has not gotten along with the family" Parent perceives child as having emotional or behavioral problems" Parent thinks that child needs or needed professional help Before age 3, child lived elsewhere or was out of caregiver's care for an extended period Teacher ratings Irritable or fighting with friends "a lot " Child's life has become less enjoyable "a lot" Teacher perceives student as having emotional or behavioral problems" Teacher thinks that student needs or needed professional help

ADHD

ADHD +ODD

ADHD+CD

'1.

9.1 0.0 12.9 17.2

48.9 28.9 60.0 50.0

50.0 16.7 41.7 33.3

14.8'" 11.I '" 16.9'" 8.3"

ADHD+ODD, ADHD+CD > ADHD ADHD+ODD, ADHD+CD > ADHD ADHD+ODD, ADHD+CD > ADHD ADHD+ODD > ADHD

12.9

41.3

41.7

7.6"

ADHD+ODD, ADHD+CD > ADHD

75.0

93.3

100

7.8"

ADHD+ODD > ADHD

15.2

41.3

50

7.8"

ADHD+ODD, ADHD+CD > ADHD

21.2 0.0

55.6 4.3

75.0 18.7

13.9'" 5.82"

ADHD+ODD, ADHD+CD > ADHD ADHD+CD > ADHD

28.1

28.9

0

4.56'

ADHD, ADHD+ODD > ADHD+CD

76.9 89.7

94.7 85.7

50 36.4

5.36' 15.9'"

ADHD, ADHD+ODD > ADHD+CD ADHD, ADHD+ODD > ADHD+CD

18.2

60.9

50.0

14.4'"

ADHD+ODD, ADHD+CD > ADHD

15.6

39.1

66.7

11.0'"

ADHD+ODD, ADHD+CD > ADHD

6.5

13.0

41.7

8.8"

ADHD+CD > ADHD, ADHD+ODD

19.4

48.7

66.7

10.3'"

ADHD+ODD, ADHD+CD > ADHD

56.3 16.1

91.3 43.5

91.7 66.7

15.3'" 11.1'"

ADHD+ODD, ADHD+CD > ADHD ADHD+ODD, ADHD+CD > ADHD

58.6

84.1

100.0

10.6'"

ADHD+ODD, ADHD+CD > ADHD

70.6

94.7

100.0

9.0'"

ADHD+ODD, ADHD+CD > ADHD

6.1

6.5

33.3

8.5"

ADHD+CD > ADHD, ADHD+ODD

19.4 26.7

43.5 55.8

66.7 50.0

9.3'" 6.2"

ADHD+ODD, ADHD+CD > ADHD ADHD+ODD > ADHD

70.0

88.4

100.0

7.1"

ADHD+ODD, ADHD+CD > ADHD

68.0

97.3

100.0

14.0'"

ADHD+ODD, ADHD+CD > ADHD

2

Proportions Test

Note: ADHD = attention-deficit hyperactivity disorder; ODD = oppositional defiant disorder, CD = conduct disorder.

During the past 6 months. Within the past year. C Within the past 4 years. 'p:5 .1; "p:5 .05; "'p:5 .01.

a

b

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with other groups was unexpected given previous research findings that indicated ODD children's rate of dysfunction was intermediate to that of ADHD and CD children (Faraone et al., 1991). It is interesting that their level of achievement was consistent with their relatively higher self-perception scores in scholastic competence (as indicated by a nonsignificant trend), suggesting that children with ADHD+ODD appear to be aware of their academic strengths. The ADHD and ADHD+CD children, on the other hand, exhibited marked academic problems. While some research examining ADHD and conduct problems has suggested a more central role between ADHD and academic underachievement (e.g., Frick et al., 1991; SemrudClikeman et al., 1992, with regard to poor reading ability). other findings examining comorbid conditions have elicited inconsistent results. For example. comparisons of ADHD+CD children with ADHD children on academic measures have found ADHD+ CD children's performance to be better (Stewart et al., 1981), similar (Matier et al., 1992), and worse (Moffitt and Henry, 1989) than that of children with "pure" ADHD. Results of the current study suggest that while ADHD may have some role in academic underachievement, the presence and type of a comorbid condition may also influence achievement progression. Furthermore. the reasons for underachievement may involve a multitude of variables. It is possible, for example, that ADHD+CD children's lack of interest in reading or their disproportionate number of school absences may detrimentally affect their achievement. This lack of opportunity to practice the necessary skills would have different treatment implications than a genuine skill deficit. In general, children with ADHD+CD were associated with the more severe correlates compared with the other groups. In addition to possessing the most

severe ADHD symptomatology, findings of the current study suggest that children with ADHD+CD are more aggressive, experience elevated rates of anxiety (irrespective of informant source), and are more likely to have mothers with psychological difficulties than children with the other DBDs. These children experience a range of problems affecting them within the home and school which appears to limit their ability to derive enjoyment out of participating in extracurricular and leisure activities. Children with ADHD+CD appear to be aware of their poor behavior and social abilities. In fact, these children's scores of self-perception were lower than those of the other groups across all domains with the exception of athletics. It appears that both comorbid groups (i.e., ADHD+ODD and ADHD+CD) derive at least some of their self-esteem from their athletic abilities. The presence of elevated ADHD ratings in children with conduct problems has been empirically documented by Schachar et al. (1986) and Abikoff et al. (1993), who found a "halo effect" operating in which teachers' ratings of ODD children contained spuriously inflated ratings of ADHD symptomatic behaviors. This issue, however, was addressed in the current study in two ways. First, classifications did not rely exclusively on teacher ratings but involved parent ratings and clinical assessment of the child. Second, rating measures used with parents and teachers required descriptive rather than evaluative judgments, a potentially effective way to reduce negative halo effects (Mintz and Collins, 1985). Should we accept that the comorbid groups did indeed meet ADHD criteria, it could still be argued that the greater severity of ADHD symptomology within the comorbid groups may confound the findings. It is unlikely, however, that this factor alone could explain the increased pathology associated with the conduct disorders. First, ADHD+ODD and

TABLE 4 Maternal Psychopathology ADHD

Global Severity Index Positive Symptom Total Positive Symptom Distress Index

ADHD+ODD

F Value

(SD)

Mean

(SD)

Mean

(SD)

df= (2,75)

Post Hoc Comparisons (Tukey B)

53,2 52.2 52.9

(10,5) (10.3) (9.2)

56.4 54.9 55.4

(10.9) (12. I) (9.4)

64 .1 62.1 59.0

(10.9) (8.6) (10.4)

4.0·· 3.1··

ADHD+CD > ADHD ADHD+CD > ADHD

Note : T scores as reported on the Symptom Checklisr-Xl-R. ADHD disorder; CD = conduct disorder. •• p :5 .0 5.

1722

ADHD+CD

Mean

J.

= attention-deficit hyperactivity

disorder ; ODD

= oppositional defiant

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O PPOSITIONAL/CONDUCT DISORDER WITH ADHD

ADHD+CD children's ADHD symptomatology was very similar and, as such, would not explain the differences noted between these groups. Second, increased symptom severity did not always correlate with higher relative pathology, as was displayed by the enhanced academic performance of ADHD+ODD children in comparison with ADHD children. Nevertheless, this study was not immune to limitations. While an unfortunate consequence of the low number of ADHD+CD children (n = 12) was reduced statistical power resulting in a limited ability to differentiate this group among others (in particular with ADHD+ODD), the significant findings that were observed attest to the degree to which differences do exist. The overrepresentation of males (as is common with studies of children with CD) may reflect a referral bias in that teachers or parents may more readily expect and identify aggression within boys than within girls. In addition, while the design of the database examined was longitudinal in nature, analyses of the current study were limited to baseline data, and as such, they constituted a cross-sectional approach. This being the case, the degree to which noted correlates were present before diagnosis remains unknown and suggests the need for further research involving a prospective approach. Finally, this study used only clinically referred children. As pointed out elsewhere (Szatmari et al., 1989), conclusions drawn with regard to correlates of a disorder from a clinically based sample must be interpreted tentatively. This is because there is no way of disentangling the correlates that are tied to assistance-seeking behavior from the correlates actually associated with the disorder itself. Future studies should include in their design nonreferred, community-based samples. It has been suggested that the comorbid condition of ADHD+ODD forms an intermediate subgroup between those with ADHD and those with ADHD+ CD (Biederman et al., 1991). The current findings lend support to the emergence of such a pattern over a number of varied domains, but at the same time acknowledge what appears to be a unique interaction between ADHD and ODD. The differences between the two comorbid groups may be attributed to the differential interaction of the comorbid disorders (i.e., ODD and CD). ADHD+CD has been shown in past studies to be a particularly unfavorable combination as the severity and persistence of these youths' antisocial behaviors and aggression often exceed those of youths

J.

with CD alone (Schachar et al., 1981; Walker et al., 1987). While the current study suggests that the comorbid disorders share some common vulnerabilities, the differential effects of comorbidity (i.e., ODD versus CD) on ADHD suggest that these subgroups are also distinct and follow a different clinical course. Consequently, they do not necessarily follow the typical hierarchy of conduct severity across all domains and certainly are not justifiably grouped together within a generic "conduct problems" category. Further support for maintaining the distinction between ODD and CD arises from Lahey et al. (1992), who noted that (1) many children with ODD never progress to CD and (2) research has suggested that the emergence of CD for the first time in adolescence appears to be independent of ODD. Rather than conceptualizing ODD and CD as developmentally staged levels of the same disorder, such findings suggest alternative pathways to disruptive CD development. Since past findings have suggested an earlier age of onset in ODD compared with CD (e.g., Loeber, 1990), future research should develop and utilize rating systems sensitive to development processes. This will assist in preventing the relationships between the disorders and symptom development as well as other relevant variables from becoming obscured. There remains a need to continue to elucidate the relationship between these two disorders and their respective correlates as well as the interactional effects of comorbid ADHD. The current study highlights the multitude of associated problems in children with DBDs, which can have a negative impact on a child's adjustment throughout his or her life. Regardless of the perspective being tapped (i.e., parent, teacher, or child), the comorbid conditions of ADHD+ODD or ADHD+CD have a marked deleterious effect on the quality of life associated with ADHD. The need for appropriate intervention using our increased syndrome-specific knowledge as a guide for effective service is essential. The increased risk for maternal psychopathology, particularly for children with ADHD+CD, underscores the need for assessment and intervention to go beyond the child alone and include the home setting. The lack of social "connectedness" experienced by both comorbid groups, but especially children with ADHD+ODD, signifies a need for support in these children's abilities to create and maintain close social relationships. ADHD+ ODD children's academic strengths and related positive

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perception of their scholastic competence should be fostered, and attempts to assist these children to generalize such positive perceptions to other areas of functioning should be made. The parallel increase in externalizing (i.e., aggression) and internalizing (i.e., anxiety) behaviors found in children with DBDs suggests that the utiliry of intervening from just one perspective in isolation may be limited. Both internalizing and externalizing problems should be addressed concurrently and in conjunction with the above-noted recommendations. Finally, other helpful strategies that can be generalized to all children with DBDs include the fostering of increased family involvement, academic development, social skills training, and behavior management.

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