Burt, S.A., McGue, M., DeMarte, J.A., Krueger, R.F. & Iacono, W.G. (2006) Timing of Menarche and the Origins of Conduct Disorder. Archives of General Psychiatry, 63, 890-896.
Context: Precocious onset of menses (ie, age _11 years) has repeatedly been identified as a risk factor for higher rates of delinquency or conduct disorder (CD) in girls. Although this association is often conceptualized as environmentally mediated (via processes such as affiliation of early-menstruating youth with older, more deviant peers), such conclusions are premature as biological and genetic explanations have yet to be fully considered.
Objective: To uncover the origins of the association between CD and timing of menarche.
Design, Setting, and Participants: The sample consisted of a population-based birth cohort of 708 midadolescent female twins assessed as part of the ongoing Minnesota Twin Family Study. We conducted 2 sets of analyses: standard bivariate analyses to uncover possible common genes and moderator analyses to evaluate possible moderation of genetic influences on CD by timing of menarche.
Main Outcome Measures: Conduct disorder was assessed via individual semistructured interviews with mothers and adolescents. Menarcheal status and age at menarche were assessed via the Pubertal Development Scale.
Results: The results argued against common genetic influences but did provide evidence of etiological moderation of CD by timing of menarche. The heritability of CD was strongest (67%) in girls with average timing of menarche (ie, age 12-13 years) and substantially weaker (8%) in those with early onset. Those with late initiation of menses (ie, age _13 years) similarly exhibited weaker genetic influences (29%). Shared environmental influences showed the opposite pattern, as they were far stronger for those with precocious and delayed onset vs those with average onset.
Conclusions: Our findings provide indirect support for psychosocial interpretations of the impact of precocious menarche and, to a lesser extent, delayed menarche on CD development. Further, they lend support to the notion that in some cases, genetic influences on psychopathology may be strongest in the “average, expectable” environment.
Arch Gen Psychiatry. 2006;63:890-896
Cukrowicz, K.C., Taylor, J., Schatschneider, C. & Iacono, W.G. (2006). Personality Differences in Children with Attention-Deficit/Hyperactivity Disorder, Conduct Disorder and Controls. Journal of Child Psychology and Psychiatry, 47, 151-159.
Background: Differences in personality profiles were examined between children who differed in their co-morbidity of externalizing disorders: attention-deficit/hyperactivity disorder (ADHD) and conduct disorder (CD).
Methods: 11- and 17-year-old male and female twins from a community sample were categorized as ADHD only, CD only, co-morbid CD-ADHD, and controls (no ADHD or CD) based on threshold and subthreshold CD and ADHD diagnoses assessed with structured interviews. Multivariate analyses were used to identify patterns of personality that differentiate these four diagnostic groups. It was hypothesized that significant differences would be found in the pattern of personality variables between participants in the co-morbid group, compared to the other three groups, and that these differences would hold across developmental periods.
Results: As expected, the co-morbid group had a pattern of personality marked by higher Negative Emotionality and lower Constraint than the other diagnostic groups. This pattern was evidenced across gender and age cohort.
Conclusions: An extreme personality profile may represent a liability toward the occurrence of ADHD and CD with more extreme profiles contributing to the occurrence of both disorders among boys and girls. Implications for treatment planning and theoretical development are discussed.
Iacono, W.G. & McGue, M. (2006) Association between P3 Event-Related Brain Potential Amplitude and Adolescent Problem Behavior. Psychophysiology, 43, 465-469.
This study examined P3 event-related brain potential amplitude and the age of onset of adolescent problem behaviors associated with the development of externalizing psychopathology. Five hundred and one male and 627 female 17-year-old twins reported whether and when they had initiated tobacco, alcohol, or illicit drug use, had police contact, or had sexual intercourse. P3 amplitude was recorded using a visual oddball task. Each of these behaviors was associated with reduced P3 amplitude. When these five behaviors were used to create a composite early problem behavior scale reflecting onset prior to age 15, higher scores were associated with smaller P3 amplitudes. P3 amplitude reduction has been associated with genetic risk for alcoholism and other externalizing disorders associated with disinhibited behavior. Our results suggest that reduced P3 may also be associated with early expression of behaviors that predict the development of these disorders.
Tackett, J.L., Krueger, R.F., Iacono, W.G., & McGue, M. (2005). Symptom-Based Subfactors of DSM-Defined Conduct Disorder: Evidence for Etiological Distinctions. Journal of Abnormal Psychology, 114, 483-487.
Past research investigating the structure of conduct disorder (CD) symptoms has provided evidence of a phenotypic distinction between aggressive and rule-breaking subfactors of CD. However, evidence of etiologic distinctions between these subfactors has not been reported to date. In the current study, the authors investigated this issue in a sample of 1,151 male twins who were 17 years of age. The results indicate that aggressive and rule-breaking CD subfactors have both common and distinct etiologic influences, with shared environmental influences playing a significant role in rule-breaking behaviors. The authors discuss implications of these findings for the assessment and treatment of CD.
Marmorstein, N.R., Malone, S.M., & Iacono, W.G. (2004). Major depression and conduct disorder in youth: Associations with parental psychopathology and parent child-conflict. Journal of Child Psychology and Psychiatry, 45, 377-386.
Background: This study examined conduct disorder (CD) and major depression (MDD) in adolescents in relationship to parent–child conflict and psychopathology in their parents.
Method: Participants were drawn from a population-based sample of twins and their families. Affected participants had lifetime diagnoses of CD and/or MDD; controls had no history of either disorder.
Results: The presence of CD or MDD in an adolescent was related to increased rates of maternal MDD and paternal antisocial behavior. Both CD and MDD in adolescents were directly associated with high parent–child conflict. This association appeared unrelated to whether the father had a history of antisocial behavior; however, the association between mother–child conflict and psychopathology in the child was related to the mother having a history of MDD as well.
Conclusion: The implications of these findings for the complex relationship between parental diagnoses, child diagnoses, and parent–child conflict are discussed.