In both the baseline and prospective analyses of characteristics of hypomania and mania, no differences between bipolar II and bipolar I subjects with and without CUD were detected. Previous studies indicated that CU in BD was associated with hypomanic and manic episodes, but not depression [8,18,20]. Also, no significant differences regarding depression episode characteristics were detected across groups with and without CUD. The statistically significant results presented in Table 4 for mania and depression, including seeking help more often from a professional, refer to differences between mania (bipolar I) and hypomania (bipolar II) or various degrees of depression in these subtypes of bipolar disorders. Further, no differences were found in several additional characteristics of bipolar I and II disorders, including rates of rapid cycling, mixed episodes and suicidal ideation and behavior. Previous studies reported higher rates of complications and more severe bipolar symptoms including more time in manic and mixed episodes [9], more frequent affective episodes [10], mixed states [22]. The differing results found in the current analysis may be due to different sample and sampling characteristics. The current sample is a high-risk family study rather than a clinical treatment sample and may therefore show different patterns of comorbidity.
