Dual Diagnosis: Serious Mental Illness and Co-Occurring Substance Use Disorders

People living with serious mental illness face numerous barriers to living a life unencumbered by their disorder. Many have the added challenge of a dual diagnosis – experiencing co-occurring serious mental illness and a substance use disorder.  A dual diagnosis can have a multitude of consequences on an individual’s life: People with co-occurring disorders are more vulnerable to becoming involved with the criminal justice system or experiencing homelessness and it is much more difficult for them to access the necessary treatment that addresses both disorders. 

Evidence-based treatments to target concurrent substance use disorder and mental illness do exist. However, most individuals face substantial barriers to accessing quality treatment. Policy solutions should include the better integration of the mental health and substance use treatment systems and an increase in the availability of integrated dual-disorder treatment programs.

Key Findings

• One in four people with serious mental illness also have a substance use disorder.
• Only 12.7% of people with co-occurring serious mental illness and substance use disorders received any treatment for both conditions in 2019.  
• People with serious mental illness are more likely to smoke tobacco and misuse alcohol compared to those without mental illness. Cannabis is one of the most common drugs used by people with serious mental illness. 
• Almost 40% of individuals with serious mental illness used marijuana in 2019.
• Individuals with co-occurring substance use disorder and serious mental illness are overrepresented in every part of the criminal justice system and are more likely to experience homelessness.