Examining the Comorbidity of Bipolar Disorder and Autism Spectrum Disorders

OBJECTIVE: Although mood dysregulation is frequently associated with autism spectrum disorders (ASD) and autistic traits are common in youth with bipolar disorder, uncertainties remain regarding the comorbid occurrence of bipolar disorder and ASD. This study examines the clinical and familial correlates of bipolar disorder when it occurs with and without ASD comorbidity in a well-characterized, research-referred population of youth with bipolar disorder. We hypothesized that in youth with bipolar disorder, the clinical and familial correlates of bipolar disorder will be comparable irrespective of the comorbidity with ASD. METHOD: Clinical correlates and familial risk were assessed by secondary analysis of the data from a large family study of youth with bipolar I disorder (diagnosis based on DSM-IV criteria; probands n = 157, relatives n = 487; study period: November 1997-September 2002). Findings in bipolar I youth were compared with those in youth with attention-deficit/hyperactivity disorder (diagnosis based on DSM-III-R criteria) without bipolar I disorder (probands n = 162, relatives n = 511) and age- and sex-matched controls without bipolar I disorder or attention-deficit/hyperactivity disorder (probands n = 136, relatives n = 411). All subjects were comprehensively assessed using structured diagnostic interviews and a wide range of nonoverlapping measures assessing multiple dimensions of functioning. RESULTS: Thirty percent (47/155) of the bipolar I probands met criteria for ASD (diagnosis based on DSM-III-R criteria). The mean ± SD age at onset of bipolar I disorder was significantly earlier in the presence of ASD comorbidity (4.7 ± 2.9 vs 6.3 ± 3.7 years; P = .01). The phenotypic and familial correlates of bipolar disorder were similar in youth with and without ASD comorbidity. CONCLUSIONS: A clinically significant minority of youth with bipolar I disorder suffers from comorbid ASD. Phenotypic and familial correlates of bipolar disorder were typical of the disorder in the presence of ASD comorbidity. Bipolar I disorder comorbidity with ASD represents a very severe psychopathologic state in youth.