Psychopathy and Conduct Problems in Children: II. Implications for Subtyping Children With Conduct Problems

Psychopathy and Conduct Problems in Children: II. Implications for Subtyping Children With Conduct Problems RACHEL E. C H RIST IAN , M.A., PAUL]. FRICK, PH.D., NATALIE L. HILL, B.A., LORI TYLER, M.A. , AND

DANA R. FRAZER, B.A.

ABSTRACT Objective: To test whether the presence of callous and unemotional (CU) traits designates a unique subgroup of children with conduct problems that corresponds more closely to adult conceptualizations of psychopathy. Method : A clinic-referred sample of 120 children between the ages of 6 and 13 years were assessed using parent and teacher ratings of CU traits, as well as parent and teacher report on a structured interview assess ing oppositional defiant disorder (ODD) and conduct disorder (CD) symptoms . Results: A cluster analysis of the ratings of CU traits and 0001 CD symptoms revealed four clusters of children , two of which had high rates of ODD and CD symptoms . One of these conduct problem clusters also exhibited high levels of CU traits (n

= 11). These

children had a greater number and

variety of conduct problems, a stronger history of police contacts, and a stronger parental history of antisocial personality disorder, despite being of higher intelligence than other children with significant conduct problems (n =29). Conclusion: The presence of CU traits with significant conduct problems seems to designate a unique SUbgroupof antisocial children who show a very severe pattern of antisocial behav ior and who correspond more closely to adult conceptualizations of psychopathy. J . Am. Acad. Child Ado/esc. Psychiatry, 1997,36(2):233-241 . Key Words: psychopathy, conduct problems, children , subtypes .

Hare, Harpur, and colleagues have developed a twofactor model of psychopathy that has proven to be useful for studying severe and chronic patterns of antisocial behavior in adults (Hare et al., 1991; Harpur et al., 1989). This model specifies two partially independent dimensions of behavior. One dimension includes the interpersonal (e.g., superficial charm, absence of lasting relationships, absence of empathy) and emotional (e.g., absence of guilt , shallow emotions, lack of anxiety) traits th at have been hallmarks of the psychopathic personality (see Cleckley, 1976 ; Hare, 1993; McCord and McCord, 1964). The second dimension includes the unstable (e.g., multiple marriages, poor employment history) and antisocial (e.g., multiple

Accepted Ap ril 26. / 996. From the Department of Psychology, Uninersity ofAlabama, TUJCaloOJa. Reprint requests to Dr. Frick, Depa rtm ent of Psychology. University of Alabama, Box 870348. Tuscaloosa, AL 3 5487.

0890-8567/97/3602-0233$03.00/0©1997 by the American Academy of Child and Adolescent Psychiatry.

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arrests, aggression) lifestyle that have been defining features ofantisocial personality disorder (APD) (American Psychiatric Association, 1994). Several studies have shown that these two dimensions are separable through factor analysis and, more importantly, they have different correlates that could suggest divergent etiologies (Hare er al., 1990; Harpur et al., 1988 , 1989). However, these two dimensions are significantly correlated (r = .53 to .56) (Hare er al., 199 I), and their occurrence in the same individual seems to designate an individual who is likely to show an especially severe and chronic pattern of antisocial behavior. For example, Hare and McPherson (1984) found that prisoners who had high ratings on psychopathic features (only about 25% to 30% of all prisoners across several studies) (Hare et al., 1991) were significantly more likely to engage in physical violence and other forms of aggressive behavior (e.g., verbal abuse, threats, intimidation) both in prison and after release. Similarly, Harris et al. (199 I) found that the rate of violent reoffending in released male prisoners was four

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times higher for prISoners who showed psychopathic features. In a previous study, we began extending this twofactor model of psychopathy to understanding children who display conduct problems (Frick et al., 1994) . Consistent with findings in adult samples , we found that in clinic-referred children there were two separable psychological dimensions. One dimension involved a callous-unemotional (CU) interpersonal style (e.g., lacks guilt, does not show empathy, does not show emotions), and the second dimension involved poor impulse control (e.g., becomes angry when corrected, acts without thinking) and antisocial behavior (e.g., engages in illegal activities). Consistent with the adult literature, the second dimension was highly associated with traditional behavioral definitions of antisocial disorders (i.e., DSM-III-R definitions of oppositional defiant disorder and conduct disorder) . However, the CU dimension was less strongly associated with conduct problem diagnoses and the CU traits had several differential correlates from conduce problem symptoms that could suggest a divergent etiology (sec also O 'Brien and Frick, 1996) . In summary, our previous study established CU traits as a separate, yet correlated (r= .50) psychological dimension to behavioral definitions of conduct problems. In the present study, our goal was to extend these findings by determining whether or not CU traits could be used to delineate a unique subgroup of children with conduct problems, a group that is more analogous to adult conceptualizations of psychopathy. It is clear that children with conduct problems constitute a very heterogeneous group (for reviews see Hinshaw et al., 1993; Lahey er al., 1992). The vast majority of subryping research has focused on the different types or patterns of conduct problems displayed. However, several subryping approaches have focused on the child's interpersonal or affective style, consistent with the concept of psychopathy. One inAuential approach that was included in two earlier versions of the DSM (American Psychiatric Association, 1980, 1987) distinguished between youths with conduct problems who (I) were capable of sustaining social relationships and who tended to commit antisocial acts with peers (socialized or group type) or (2) were not able to maintain interpersonal relations and who tended to commit antisocial acts alone (undersocialized or solitary type). Also, several studies have

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shown that children with conduct problems who do not show elevated levels of anxiety constitute a unique and potentially more severe subgroup of antisocial children (McBurnett et al., 1991; O 'Brien et al., 1994; Quay, 1987; Walker et al., 1991). Both of these lines of research focused on certain aspects of the interpersonal and affective characteristics of psychopathy. An assessment approach that incorporates the complete constellation of these traits could help to unify these separate lines of research and designate a distinct group of children with conduct problems that more closely approximates the construct of psychopathy, as it has been used in adults. This could be important not only for predictive purposes but also for designating a group of children who may have unique causal factors involved in the development of the conduct problem behavior (Frick, in press; Newman and Wallace, 1993). Therefore, the main question to be addressed in this study is whether or not the presence of CU traits designates a subgroup of children with conduct problems who show a severe pattern of antisocial behavior.

METHOD Subjects The sample consisted of 120 children between the ages of 6 and 13 years (mean; 8.7. SD ; 2.1) who were consecutive referrals to a university. based outpatient diagnostic and referral service. This service provides comprehensive psychological evaluations to children with severe emotional. behavioral. or learning problems who are then referred to appropriate agencies for intervention. Therefore. more than two thirds of the sample had not had any psychiatric or psychological treatment prior to their evaluation . Of 131 consecutive referrals within the target age range, 7 were excluded because of mental retardation and 4 because of incomplete data collection. A summary of the sample characteristics is provided in T able I.

Measures

Psychopathy Screening Device. The Psychopathy Screening Device (PSD) (Frick and Hare. in press) is a 20-item behavior rating scale that was completed by each child's parent and teacher . It was designed to be a childhood extension of the Psychopathy ChecklistRevised (Hare . 1991) . Each item on the PSD is scored either 0 ("not at all true"), 1 ("sometimes true "), or 2 ("definitely true"). Frick et al. (1994) found that the PSD cont ained two factors: a 6-item Callous/Unemotional (CU) factor and a IO-item Impulsiv ity/Conduct Problems (I/CP) factor. For the purposes of this study. items that loaded significantly and uniquely on each factor were placed into scales that possessed adequate internal consisten cy (CU ; .73 ; I/CP ; .83). In a communiry sample of preadolescent children, the I-week test-retest reliability of the teacher version of

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TABLE 1 Demographic Characteristics of the Sample (N; 120) Age, years (SO) Gender (% male)

8.68 (2.07) 6.0-13.9 80

Erhniciry % African-American % Non-Hispanic Caucasian Duncan's Socioeconomic Index (SO) Range Yearly family income (SO) Range Full Scale IQ (SO) Range Diagnosis (%) ADHD CD ODD CD or ODD ANX DEP

21 79 37.84 (24.67)

0-96 29,22 I (26,772) 900-156,000 94.39 (I 3.0 I) 71-141 89 16 38 38 48

9

Note: Socioeconomic status was measured using Duncan's Socioeconomic Index (Mueller and Parcel, 1981). Full Scale IQ is based on the WISC-R (Wechsler, 1974) or the WISC-I1I (Wechsler, 199 I) for a portion of the sample. Diagnoses of attention-deficit hyperactivity disorder (ADHD), conduct disorder (CD), and oppositional defiant disorder (ODD) are based on DSM-III-R criteria using parent and teacher report on the Diagnostic Interview Schedule for Children, Version 2.3 (Shaffer er al., 1992). Anxiety diagnoses (ANX) include the DSM-III-R diagnoses of simple phobia, social phobia, overanxious disorder, and separation anxiety disorder using parent report only. Depression diagnoses (DEP) include the DSM-Ill-Rdiagnoses of major depression and dysthymia using parent report only.

the scale resulted in reliability coefficients of .87 for the I/CP scale and .73 for the CU scale (McBurnett et al., 1994). In this study, we felt strongly that a combination of parent and teacher report on the PSD should be used in analyses for several reasons. First, Frick er al. (I994) reported similar two-factor structures for both parent and teacher report on the PSD, and in the present sample the correlation between parent and teacher reports was .31 (p < .001) on the CU scale and .29 (p < .00 I) on the ItCP scale. Second, there is evidence that the inconsistency across different informants in assessing child psychopathology is largely due to informants seeing the child in different settings, not necessarily due to idiosyncratic informant biases (Achenbach et al., 1987). Therefore, relying on any single informant reduces the validity of the assessment by not including information on a child's functioning in multiple settings. Third, we wanted the method of assessing the constructs on the PSD to be analogous to the assessment of DSM-III-R conduct problem symptoms, where research has clearly shown that parents and teachers provide unique and important assessment information (Loeber et al., 1991). Diagnostic Interview Schedule[or Children. The National Institute of Mental Health Diagnostic Interview Schedule for Children, Version 2.3 (DISC-2.3) (Shaffer er al., 1992) was used to assess all of the symptoms included in the criteria for ODD and CD in the DSM-III-R (American Psychiatric Association, 1987). A separate DISC-2.3 interview was administered to one of the child's

custodial parents and the child's teacher. A symptom was considered present if it was endorsed by either the teacher or parent. The correlation between parent and teacher report of ODD and CD symptoms was ,33 (p < .001). In addition to assessing all symptoms necessary to make a diagnosis of ODD and CD, the parent version assesses the parent's estimate of the age at which each CD symptom displayed by the child was first evident. The DISC-2,3 was administered by either a clinical psychologist or an advanced doctoral student in clinical psychology who had completed at least two assessment courses and who had been trained in standard administration procedures for the DISC. To check the reliability of this procedure, approximately 25% of the parent DISC interviews were observed through one-way mirrors and the parents' responses were independently coded by an observer. The K coefficient was used to determine interviewer-observer agreement for each symptom of ODD and CD. The median f( for ODD symptoms was 1.0 (range .91 to 1.0) and the median K for CD symptoms was also 1.0 (range .79 to 1.0). Police Contact and School Suspensions. A child's conAict with social institutions was assessed in two ways, both based on parental report in an unstructured interview. First, the child's parent provided information on the number of police contacts the child has had throughout his or her life. Second, the child's parent estimated the lifetime number of school suspensions, including both inschool and out-of-school suspensions. Because the distributions of both of these variables were highly skewed in our sample (i.e., the majority of children had no police contacts or school suspensions), these two variables were coded dichotomously based on whether or not the child had ever been in contact with the police and whether or not the child had ever been suspended from school. Parental History of Antisocial Personality Disorder. A parental history of APD according to DSM-III-Rcriteria (American Psychiatric Association, 1987) was assessed for all children who were currently living with at least one biological parent (n; I 17). The diagnoses were based on the relevant section of the Diagnostic Interview Schedule-Version III-A (DIS-IlIA) (Robins and Helzer, 1985). The DIS was administered by doctoral students in clinical psychology who had completed a class in the assessment of adult psychopathology and who were trained in standardized administration procedures. All interviewers were blind to the child's diagnostic status, his or her scores on the PSD, and the reason the child was referred for an evaluation. To assess the reliability of the interviews, 33% of the interviews were observed via one-way mirrors with observers and interviewers independently determining the presence of an APD diagnosis. The K for interviewer-observer agreement on a maternal diagnosis of APD was .79 and on a paternal diagnosis of APD was .93. In 22% of the cases, the child's biological father was interviewed directly, and in 85% of the cases the child's biological mother was interviewed directly. In all cases in which the biological parent could not be interviewed directly, the child's other biological parent served as the informant to make the APD diagnosis. Therefore, similar to past research on family histories of APD (e.g., Biederman et al., 1987; Lahey et al., 1988), assessment of paternal APD was often based solely on the mother's report. The use of this methodology was felt to be justifiable for two reasons. First, owing to the nature of antisocial disorders in which there tends to be a bias to minimize symptoms, report of significant others should play an important tole in the assessment of APD (Hare, 1985). Second, a significant number of the fathers (n ; 29) who could not be interviewed directly agreed to complete by mail the 54-item Socialization scale of the California Personality Inventory (Gough,

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1%9), which is often used as a self-repo rt indicator of APD (Hare. 1985) . Within this subsarnple, fathers who met criteria for APD according to maternal repon (n = 5) scored significantly lower on the Socialization scale than fathers who did not meet criteria for APD according to maternal repon (n = 24) (t[271 = 2.63. p < .0 I) . Therefore. there was empirical suppon for the validity of this family history method for assessing paternal APD . In fact, this is likely a low estimate of validity given that fathers with APD were disproportionately less likely to be available and willing to complete the Socialization scale. leading to a restricted range of scores.

Procedure Each child was accompanied to the evaluation by at least one custodial parent, in most cases the mother. The parent gave informed consent for all of the information to be used in research in an anonymous fashion and each ch ild gave his or her assent . Parents were told that their consent was strictly voluntary and that it would in no way affect the clinical services that they received. After informed consent was provided. the semistructured background interview was administered to the parent to obtain demographic information and information on police contacts and school suspensions. The DIS C-P interview was then administered to the parent. after which he or she completed the PSD . After a break for lunch. the parent returned and completed the DIS interv iew. After the assent procedure. the WISC-R (n = 102) or WISC-III (n = 29) was administered ro the children (Wechsler, 1974 , 1991). Within the week after this evaluation. the DISC-T was administered to the child 's teacher by the same interviewer who had administered the parent DISC. The PSD was mailed to the teacher with a selfaddressed. stamped envelope.

RESULTS

Children's scores on the CU and VCP scales of the PSO and their total number of conduct problem symptoms were first standardized (converted to zscores) and then subjected to cluster analysis. The Statistical Analysis System clustering procedure FASTCLUS, which places subjects into disjoint clusters (i.e., each subject is placed into one and only one cluster based on similarity of scores with others in the cluster), was used for this analysis. The FASTCLUS procedure uses the nearest centroid sorting method of forming clusters (Bernstein, 1988). On the basis of a scree plot of the explained variance (R 2 ) with increasing clusters, a fourcluster solution was chosen as being most justifiable. This four-cluster solution (R 2 = .622) resulted in one cluster that was well below the mean on all three variables (clinic control; n = 39), a second cluster that was above the mean on the CU scale but low on the vcr scale and low on the number of conduct problem symptoms (callous-unemotional; n = 4 I), a third cluster that was high on both the VCP scale and number of conduct problem symptoms but below the mean on

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the CU scale (impulsive conduct problems; n = 29), and a fourth group that was high on all three variables (psychopathic conduct problems; n = II). When a five-cluster solution was inspected, not only was this solution less justifiable on statistical grounds, but the fifth cluster resulted in a division of the clinic control cluster into two groups, each with scores below the mean on all three variables. A comparison of the four clusters on demographic variables and their correspondence with DSM-///-R diagnoses is provided in Table 2. The two conduct problem clusters accounted for all of the children with a diagnosis of CO and the majority of children with 000. The clusters differed on mean socioeconomic status (F[3,116] = 3.69, P < .0 I), although pairwise comparisons using Tukey's procedure did not reveal any significant differences between groups. The clusters also differed on intelligence (F[3.116] = 7.31. P < .00 I). The impulsive conduct problems cluster had lower IQ scores than both the clinic control and psychopathic conduct problems clusters. An univariate analysis of covariance was conducted comparing the four clusters of children on several indices of severity and on the presence of different types of conduct problems. The variables of socioeconomic status, Full Scale IQ, age, and gender were all used as covariates in these analyses. The primary comparison of interest was between the two conduct problem clusters. Because the conduct problem clusters were formed using 000 and CO symptoms, one would expect differences between the two conduct problem clusters and the two non-eonduct problem clusters. The results of these analyses are reported in Table 3. They indicate that the psychopathic conduct problems cluster differed from the impulsive conduct problems cluster on three of the four indices of severity. The psychopathic cluster had more symptoms of 000 and CO and higher scores on the Aggression and Delinquency scales of the Child Behavior Checklist1991 version (Achenbach, 199 I). Also, to determine whether the groups differed on the types of conduct problems exhibited, conduct problems were grouped into four symptom types based on the meta-analysis conducted by Frick et al. (I 993). Each child was assigned a score based on the total number of behaviors within each symptom category that were judged to be present by either parent or teacher.

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TABLE 2 Comparison of Four Cluste rs on Demographi c Variables and DSM-III-R D iagnoses C linic Control Cluster ( n =39)

CallousUn emotional C luster (n =4 1)

Impuls ive Conduct Cluster

Age (SO)

8.2 1 (1.72)

8.66 (1.9 1)

8.87 (2.64 )

9.88 (1.72)

SES (SO )

47.61" (22.54)

30.0 1a (24.68)

36.20 a (22.57)

36 .46 a (28.58)

3.69"

Full Scale IQ (SO)

100.49" (13.93)

9 1.24ab

88.52 b (10.66)

100.00· (14.68)

7.3 1'"

( 10.29)

( n =29)

Psychopathic Conduct Clu ster (n = l l)

RJ .116) 2.03

x'

(3, n = 120)

Gende r (% male)

77

Eth niciry (% African- Ame rican ) ODD (%) C D (% ) Either O DD o r C D (% ) ADHD (%)

11 5 0 5 74

76 24 15 0 15 92

90 28 90 45 90 100

82 27 100 55 100 100

2.44 4.04 78.58' " 45 .71'" 78.58' "

I4.2Y·

Note: Mean s with different superscripts were significantl y d ifferent (p < .0 5) in pairwise comparisons using T ukey's procedur e. SES = socioecono mic status; ODD = oppositional defiant disorder ; C D = conduct disorder; ADHD = attention-deficit hyperactiviry disorder. •• p < .0 1; ••• P < .00 1.

Comparisons across clusters are reported in Table 3. Consistent with predictions, the results ind icated that the psychopathic conduct problems cluster showed greater numbers of oppositional, aggressive, and covert property-destructive symptoms than the impulsive conduct problems cluster. The pairwise comparison between the two conduct problem clusters on the number of status offense symptoms approached statistical significance (p < .08) . The two conduct problem clusters were also compared on the earliest age at which any of the CD sympto ms were reported as being present by the child 's parent. This analysis was limited to only the two conduct problem clusters and to onl y child ren in the two clusters who displayed at least one CO symptom. Contrary to predictions, children in the two clusters did not differ on parental report of the onset of the first CD symptom (F[5,22J = .50, P not significant). The psychopathic cond uct problems cluster had a mean onset of first symptom at 5.44 years (SO = 1.57) after adjusting for the covariates, and the impulsive conduct problems cluster had a mean onset of first symptom at 6.24 years (SO = 3.0). The four clusters were compared on the percentage of children in each group with a history of school suspensions, a history of police contacts, and a parental

history of APO , using logistic regression to cont rol for demographic variables. These dependent measures were not confounded with the method of group formation , as was the case in the previous analyses, and therefore, comparisons with the non-eonduct problem clusters are more meaningful. These results are sum marized in T able 4. For both a history of police contact and a parental history of APO , the psychopathic conduct probl ems cluster differed significantly from both the clinic control and callous-unemotional clusters. In contrast , the impulsive conduct problems cluster did not differ from the clinic control cluster on either variable. However, the difference between the two conduct problems clusters did not reach stat istical significance, although there was a trend in the expected direc tion for both police contacts (X2 [1, n = 40J = 3.27, p < .07) and parental APO (X 2 [1, n = 39] = 2.88, P < .09), with the psychopath ic group having 2. 5 times the rate of police contacts (36% versus 14%) and almost 3 times the rate of parental APO (40% versus 14%) . The odds of having a history ofschool suspension showed a different pattern across the clusters with the callous-unemotional, impulsi ve conduct problems, and psychopathic conduct problems clusters all having a higher rate of school suspensions than the clinic control cluster.

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TABLE 3 Comparison of Four Clu sters on Indices of Severity and Type of Conduct Problems

PSD Scales CU scale of PSD (SO) I/CP scale of PSD (SO) Severity No . DSM-III-R symp toms of ODD/CD (SO) OCD scale of CBR SC (SO) Agg scale of C BC L (SO) Del scale of C BC L (SO) Type of conduct problems Oppositional symptoms (SO) Aggression symptoms (SO) Covert prop erry-desrruc rive sympto ms (SO ) Status offense symptoms (SO )

Clin ic Control Cluster (n = 38)

CallousUnemotional Cluster (n = 41) b

Impulsi ve Conduct Cluster (n = 29)

Psychopathic Conduct Cluster (n = II) d

R3,116)

5.27" (2.27) 7.89" (2.93)

10.20 (2.34) 13.92 b (3.55)

8.44 ' (2.33) 19.94' (3.69)

16.06 ( 1.94) 22.35' (3.69)

68 .81'"

1.35" (1.64) 20.20" (6.47) 5.66" (4.84) 1.35" (1.09 )

3.42 b (2. 12) 26.31 b (9.10) 12.20 b (5.84) 2.87 b (1.81)

8.78' (2.5 1) 37.22 ' (10.81) 17.82' (9.45) 4.29' (3. 19)

II.37 d (2.89) 39.33 ' (11.87) 22.79 d (9.55) 7.90 d (7.02)

97.03'"

1.00" (1.40) 0.23 " (0.38) 0.09" (0.27) 0.06" (0. 16)

2.5Y

5.57' ( 1.32) 1.88' (1.22) 1.11' (0.83) 0.43 b (0.74)

6.82 d (0.8 I) 2.50 d (1.57) 1.8Y (0.75) 0.7Y (0.87)

76.71'"

(1.68) 0.25 " (0.61) 0.62 b (0.70) 0.10" (0.30)

80.68 '"

23.38'" 22.29'" 16.00'"

40.78'" 24.22'" 8.06' "

NOt(: Comparisons were conducted controlling for the variables socioeconomic status, age, Full Scale IQ. and gender. Least-square means adjusted for the covariates are reported. Values with different superscripts were significantly different (p < .05) in pairwise comparisons using Tukey's procedure. PSD = Psychopathy Screening Device; CBRSC = Comprehensive Behavior Rating Scale for Children; CBCL = C hild Behavior Checklisr -l Sv l version ; C U =Callous/Unemotional; I1CP = Impulsivity/Conduct Problems; ODD = oppositional defiant disorde r; CD = conduct disorder; OCD = Oppositional/Conduct Disorder; Agg = Aggression ; Del = Delinquency. ". p < .00 I.

DISCUSSION

In our previous study (Frick er al., 1994) which used a partially overlapping sample (64 children were common to both stud ies), we found that CU traits were partiall y independent from DSM-/Il-R symptoms of conduct problems and these two dimensions accounted for unique variance in several important criterion variables. In the present study, we extended these findings by addressing the question of whether a subgroup of children with conduct problems could be isolated that more closely approximates the way " psychopathy" is conceptualized in adults (Hare et al., 1991 ; Harpur et al., 1989). Consistent with our hypotheses, a cluster analysis isolated a distinct cluster of children who exhibited high rates of conduct problems (all of whom had diagnoses of either ODD or CD) who also showed high scores on the CU dimension . This

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subgroup of children, albeit a minority of children with conduct problem diagnoses . showed several character istics of theoretical and practical interest. The cluster of children with conduct problems who also exhibited CU traits . which we labeled as the psychopathic conduct problems cluster, exhibited significantly more conduct problems and a greater variety of conduct problems than children with conduct problems who did not show CU traits (the impulsive conduct problems cluster) . These findings are important because Loeber (I982. 1991), in his reviews of longitudinal research, found that the number of conduct problems displayed is one of the best predictors of the stability of a child 's antisocial behavior into adolescence and adulthood. Similarly. Loeber and Schmaling (I985) found that children who exhibited both overt (e.g.• fighting) and covert (e.g.• stealing) types of antisocial

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TABLE 4 Comparison of Four Clusters on History of School Suspensions. History of Police Contacts, and Parental History of Ant isocial Personaliry Disorder

Lifetime school suspensions (%) Lifetime police contacts (%) Parent with APD (%)

Clinic Control Cluster (n; 39)

CallousUnemotional Cluster (n;4I)

Impulsive Conduct Cluster (n;29)

Psychopathic Conduct Cluster (n; 1I)

3"

22 b

55' 36 b (n = 10)

9.33· 6.13·

40 b

S.4S·

0" (n; 39)

(n ; 39)

35 b• I4 ab (n; 29)

S"

lOa

14 ab

5"

Xl (3, N; 120)

Note : Overall comparisons were conducted using a logistic regression to control for socioeconomic status, Full Scale IQ. age. and gender. The sample size differed for the analyses of parental antisocial personaliry disorder (APD) because of the exclusion of three children for whom a biologi cal parent was not available to provide a family history. Values with different superscripts were significantly different (p < .05) in pairw ise comparisons using logistic regression . • p < .0 5.

behavior (labeled "versatile antisocial") tended to show a more severe and chronic partern of antisocial behavior than children who displayed either type of conduct problem in isolation. Children in the psychopathic conduct problems cluster also differed from children without conduct problems on the rate of police contact and a parental history of APO, whereas children in the impulsive conduct problems cluster did not. These findings provide further support for the greater severity of antisocial behavior in the psychopathic conduct problems cluster. Research has consistently shown that one of the best predictors of recidivism in a delinquent population is an early age of first offense, usually defined as being before age 11 or 12 years (Loeber and Srouthamer-Loeber, 1987). The age distribution of our sample (mean = 8.7 years, SO = 2.0) suggests that the vast majority of the sample fell below this critical age for first police contact. Also, a high rate of APO in biological parents has been shown to predict persistence of antisocial behavior (Lahey et al., 1995). That the impulsive conduct problems cluster, which accounted for the largest number of children with a conduct problem diagnosis, did not differ from non--eonduct problem children on this variable suggests that the intergenerationallink to antisocial behavior that has been consistently found in past research (see Frick, 1994) may largely apply to children with conduct problems who also show CU traits. This unique link co APO illustrates the fact that in addition to designating a more severe group of children with conduct problems, CU traits may also designate

a group ofchildren who develop their conduct problems as a result of different causal factors (see also Frick, in press; Newman and Wallace, 1993). Potentially different causal pathways could also account for the differences found on a measure of imelligence. The psychopathic conduct problems cluster had higher intelligence scores than the impulsive conduct problems cluster and did not differ significantly from the clinic control cluster. Therefore, lower intelligence and all of the potential mechanisms that have been hypothesized to account for its role in the development of conduct problems (see Moffitt, 1993) may apply only to children with conduct problems who do not show CU traits. The differential relationship across clusters on intelli gence and parental APO could also explain the intriguing and unexpected findings in the 4-year longitudinal study of conduct disorders reported by Lahey et al. (1995). These authors found an interaction between parental APO and intelligence for predicting the persistence of conduct disorders. That is, children with high intelligence showed less persistence in their conduct problem behavior onlyin theabsence ofparenta/ APD. In contrast, children with higher intelligence who also had a parent with APO showed the highest persistence rates in the study. Extrapolating from the present study, this group of children with high intelligence and a parental history of APO would fit the characteristics of our psychopathic conduct problems cluster. One of the few indices of severity that was not associated with the psychopathic conduct problems

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group was an earlier age at ons et of CD symptoms (sec Loeber. 1982. 1991). This failure to find differences in the age at which th e first CD symptom developed is likely due to the young age of the sample. Most studies have found that onset before age 1 I or 12 years is associated with increased persistence of antisocial beh avior (sec Hinshaw et al., 1993). The vast majority of our sample fell into this early-on set category. Therefore. within thi s restricted age range, CU traits did not predict an " extremely early" age of onset. However, within this early-onset sam ple, the se traits did designate a group of children who showed many of the other characteristics that have been associated with persistence. As a result. it may be thi s subgroup th at accounts for the higher rate of persistence in yo unger samples. This possibiliry can only be tested in longitudin al studies using samples with a greater age range than was used in th is study. In addition to the restricted age range. several other methodological limitations need to be considered in interpreting th ese findings. First . the low base rates of police contacts in this yo ung sample and the low base rates of parental APD mean that differences in only a few cases could dramatically alter the result s. Therefore, these findings need replication in larger sam ples. Second . our sample was a clinic-referred sample and. like mo st outpatient child mental clinics. it consi sted largely of boys. Also. the sampl e was predominantly from lower socioeconomic classes and from rural and semirural communities. As a result. these results need to be replicated in vario us samples to det ermine their gener alizabiliry . Third. findings regarding the callous-unemotional cluster. the clust er with so mewhat high scores on the CU scale but low rates of conduct problems. are difficult to interpret. This substantial group of children (34% of the sample) showed only moderate elevations on the CU scale (a mean z score of .43) that was dram aticall y lower than the CU sco res in th e psychopathic conduct problems group (mean z score of 1.86) . These results from the cluster analysis suggest that in our sample very high scores on the CU scale are rare and. when they do occur, the y often are associated with severe conduct problems. It would be theoretically interesting to see whether this same distribution was found in nonreferred populations, since children with high sco res on the CU scale in the absence of conduct problems may not be referred to mental health clinics. Fourth, we used cluster analyses

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form our groups rather than DSM-III-R diagnostic thresholds. Therefore. our results may not generalize exactly to children with ODD and CD diagnoses using strict DSM-III-R criteria. However, as we illustrated in Table 2. there was extremely high correspondence between the groups formed in the cluster analyses and DSM-IIJ-R diagnoses of ODD and CD. Because of these limitations, these results need to be replicated. However. they have several important clinical implications. These findings extend the results of our prev ious study (Frick et al., 1994) in suggesting th at the two-fa ctor model of psychopathy used in the adult literature may be im po rtant for understanding severe patterns of conduct problems in child ren. Specifically. there seems to be a un ique subgroup of children with conduct problems who also show CU traits who seem to fit more closely with the conceptualization of psychopathy used in ad ults. This subgroup actually account s for a minority of children with a conduct problem diagnosis. This calls into question the common practice of considering conduct disorders in general as being childhood manifestations of psychopathy (Hinshaw. 1994). Consistent with adult conceptualizations of psychopathy. this unique profile of high rates of conduct problems combined with significant CU traits seems to designate a group of children with an especially severe pattern of antisocial behavior that may warrant more intensive intervention efforts. Finally. this model of subryping children with conduct problems could be an important vehicle for studying unique causal factor s associated with distinct groups of children with conduct disorders (Frick, in press). to

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