The strong relationship between bipolar and substance-use disorder.

Bipolar disorder and substance-use disorders commonly occur in the same individual. In fact, bipolar disorder has a higher prevalence of substance-use disorders than any other psychiatric illness. Individuals with both disorders have a more severe course of bipolar disorder, including earlier onset, more frequent episodes, and more complications, including anxiety- and stress-related disorders, aggressive behavior, legal problems, and suicide. Bipolar and substance-use disorders share common mechanisms, including impulsivity, poor modulation of motivation and responses to rewarding stimuli, and susceptibility to behavioral sensitization. Studies of potential treatments for bipolar substance-use disorder have paid scant attention to the combined disorders. The most promising treatment strategies are those that address their shared mechanisms.