Wave 2 data enabled investigators to examine the effects of comorbidity prospectively, providing clear information on the direction of effect. The first NESARC incidence study, from 2009 [12], indicated that mood (major depressive disorder, bipolar 1) and anxiety disorders (panic, generalized anxiety) were significant predictors of incident alcohol and drug disorders before controlling for comorbidity, but not after. Incident substance use per se was not examined. Among incident mood and anxiety disorders, only alcohol dependence predicted bipolar 1 disorder, and this was prior to but not after comorbidity control [12]. These important findings left many questions open.
