The co-occurrence of substance use and mental health disorders is referred to as a dual diagnosis. According to the Substance Abuse and Mental Health Services Administration, nearly 8 million U.S. adults had a dual diagnosis in 2014.

Individuals who struggle with a dual diagnosis have a more complicated treatment plan, as both disorders must be addressed and treated simultaneously. Depending on the specific combination of disorders, such as alcoholism and depression or opioid addiction and anxiety, or any pairing of co-occurring disorders, the treatment approach will vary.

There are two scenarios where a dual diagnosis can develop:

The mental health disorder emerges first. When someone is struggling with a mental health disorder, such as depression, an anxiety disorder, or bipolar disorder they may use drugs or alcohol to self-medicate the unpleasant emotional state they are experiencing. Over time tolerance to the substance increases and the individual increases consumption, which then evolves into a secondary substance use disorder. The substance use disorder emerges first. Someone who becomes addiction or chemically dependent on a substance may eventually experience any number of negative consequences directly related to the substance use disorder. As these consequences take their toll, the individual may begin to develop symptoms of depression or anxiety in response to the added stress the addiction has caused.

Whichever order the two disorders occur in, the result is the same: untreated substance abuse will worsen the symptoms of the mental health disorder, and untreated mental health disorders worsen an addiction.