Few studies, however, used a prospective design (follow-up between 1 to 3 years) to investigate the course of both comorbid disorders. Results from previous research from retrospective and cross-sectional designs indicate a more severe course of comorbid bipolar disorder and CUD [30], more comorbidity [21], more psychopathological symptoms and poorer functional outcome [31]. Importantly, CU was associated with a higher rate of cannabis and other SUDs in an epidemiological prospective study in non-comorbid individuals [32].
