Epidemiologic studies have shown a significantly greater likelihood of substance misuse in persons with psychiatric disorders. One of the largest studies showed that 60.7% of people with bipolar I disorder had a lifetime diagnosis of a substance use disorder (SUD). Moreover, 32% of individuals with any mood disorder, including depression, were found to suffer from substance abuse or dependence. In general population surveys, it has been found that the presence of a mood disorder at least doubles the odds of having SUD.

Co-occurring psychiatric and alcohol use disorders can have devastating personal and societal effects, yet little evidence exists to guide clinical treatment. In the face of scant data, individual practitioners must rely instead on professional experience and those limited practice guidelines that currently exist. The American Psychiatric Association (APA) advises that failure to treat a concurrent psychiatric disorder reduces the likelihood that the treatment for a substance use disorder (SUD) will be effective. Indeed, the effects of nontreatment were demonstrated in a prospective study assessing alcohol-dependent patients for 1 year following hospitalization for alcohol dependence, in which untreated depression was directly associated with a shorter time to first drink. The results also showed that among those patients with depression (Slide 1), taking antidepressants at the time of discharge increased the likelihood of an individual remaining abstinent during the follow-up period.

Given the frequency with which patients with substance use disorders (SUDs) and those with psychiatric disorders, such as major depressive disorder (MDD) and generalized anxiety disorder (GAD), suffer relapses and recurrences, the issue of long-term treatment for SUDs warrants special attention. Faced with recommending long-term treatment, the clinician must discern the primacy of disorder, which may have been only obliquely addressed at the time of the patient's presentation and then solved by concurrent treatment. Establishing primacy relies on determining whether the psychiatric symptoms were induced by SUD or the psychiatric disorder emerged first and substance use was a means of coping with it. A third possibility exists—that the two disorders developed independently of each other, albeit becoming intermingled over time and serving to exacerbate each other. Clues to the temporal relationship of the disorders can be deduced from a meticulous history obtained from multiple sources, the effects that acute treatment has had on either condition, and the patient's willingness to remain abstinent from the addictive substance. Hasin and colleagues demonstrated the importance that a history of depression has on long-term remission and relapse outcomes in substance dependence (Slide 1).

Primary care physicians (PCPs) often provide the first line of care for the vast number of United States adults—∼30% at any given time—with either a psychiatric or a substance use disorder, or both. The widespread prevalence of this comorbidity bears reiterating: During the same 12-month period, 20% of national survey respondents with a substance use disorder (SUD) had at least one mood disorder, and 17% had at least one anxiety disorder. Conversely, at least one SUD was found among 20% of respondents with a mood disorder and 15% of those with an anxiety disorder. However, because PCPs are often not aware of or alerted to these problems, it would seem advisable that patients presenting with either a psychiatric or an alcohol use disorder should be evaluated for both conditions. Establishing the presence of co-occurring disorders may be difficult, but it is necessary for appropriate and realistic treatment planning.