Few studies hitherto used a prospective design (follow-up between 1 to 3 years) to investigate the course of both comorbid disorders [21,30,31]. In contrast to these studies, few results in this sample support the hypothesis that comorbid CUD cause more severe course of bipolar disorder [30]. However, the higher rates of psychopathology and social functioning could be replicated [31]. Higher rates of comorbidity were found for comorbid PTSD in CUD—bipolar I subjects but no more other anxiety disorders. As with a prospective study [21], higher rates of alcohol- and other substance dependence were detected in the current study while rates of manic and hypomanic syndromes did not differ across bipolar Groups 1 to 4.
