Comorbid Bipolar I Disorder and Conduct Disorder May Represent a Distinct Familial Subtype

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Comorbid bipolar I disorder and conduct disorder may represent a distinct familial subtype, providing valuable information for future clinicians.

Comorbidity with both bipolar-I (BP-I) disorder and conduct disorder (CD) occurs frequently, and the combined condition appears to represent a distinct clinical subtype, according to a study published in Acta Psychiatrica Scandinavica. Furthermore, children with symptoms of both BP-I and CD may have both full disorders, in opposition to previous hypotheses suggesting that BP-I is frequently misdiagnosed for CD, and vice versa.

Janet Wozniak, MD, from the Pediatric Psychopharmacology Program, Division of Child Psychiatry, Massachusetts General Hospital, and the Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, and colleagues investigated the association between pediatric BP-I and CD, using a familial risk analysis. The goal was to gain insight into the nature of the association between these disorders by examining the manner in which they occur in families.

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The investigators compared the diagnoses in relatives of youth in 4 proband groups, those:

  • With neither BP-I nor CD (550 probands; 1656 relatives; No CD+No BP-I)
  • With CD but without BP-I (40 probands; 127 relatives; CD+No BP-I)
  • With BP-I but without CD (197 probands; 579 relatives; BP-I+No CD)
  • With both CD and BP-I (176 probands; 488 relatives; CD+BP-I)

In all 4 studies, psychiatric assessments of subjects were made using the Kiddie Schedule for Affective Disorders-Epidemiologic Version. Diagnoses were based on independent interviews with parents and direct interviews with children older than 12 years. Assessments of adult siblings and parents aged 18 years or older were made with the Structured Clinical Interview for DSM-IV. Researchers used the combined category of either conduct disorder or antisocial personality disorder (ASPD) or both when analyzing adult first-degree relatives.

Analysis showed significant differences among the groups for the rate of CD/ASPD (X23=32.14; P <.001). First-degree relatives in the CD+BP-I group had significantly higher rates of CD/ASPD than those in the No CD+No BP-I group, whereas those in the CD+No BP-I group had higher rates of CD/ASPD compared with those in the No CD+No BP-I group and the BP-I+No CD group.

In looking at the rate of BP-I in first-degree relatives, there also were significant differences among the groups (X23=77.78; P <.001). Both the BP-I+No CD and the CD+BP-I groups had higher rates of BP-I in relatives compared with the CD+No BP-I and No CD+No BP-I groups.

When the sample was restricted to the first-degree relatives of probands with CD+BP-I and the relatives were stratified by BP-I status, the investigators found that the relatives with BP-I had a significantly higher rate of CD/ASPD compared with the relatives without BP-I (X23=37.51; P <.001).

Researchers stated that these findings have significant clinical implications. At this time, no approved pharmacological treatment exists for CD, but there are approved therapies for BP-I disorder. Researchers reported that remission of BP-I disorder has been associated with remission of CD, which suggests that in comorbid cases, treatment may prove effective. In addition, adolescents with bipolar disorder and comorbid CD were recently reported to be at a significantly increased risk for substance use disorders. Researchers suggested that identifying BP-I in youth with CD offers a tangible opportunity to mitigate aggression, addiction, and antisocial behavior in a large subgroup.

The study is limited by the retrospective nature of diagnoses of CD and ASPD in relatives and the inclusion of probands and relatives from 4 different data sets.

Researchers concluded, “Despite these limitations, our findings confirm and extend previous research supporting the notion that BP-I disorder and CD are frequently comorbid with each other…The finding of co-segregation between BP-I disorder and CD is consistent with the hypothesis that the combined condition represents a distinct subtype of either disorder.”


Wozniak J, Wilens T, DiSalvo M, et al. Comorbidity of bipolar-I disorder and conduct disorder: a familial risk analysis [published online February 13, 2019]. Acta Psychiatr Scand. doi: 10.1111/acps.13013