Co-occurring disorders, also known as comorbidities, are mental health disorders that coexist with substance use disorders (SUDs). People with mental health disorders such as anxiety, depression, or post-traumatic stress disorder (PTSD) may use drugs or alcohol as a form of self-medication. According to SAMHSA’s 2021 National Survey on Drug Use and Health, approximately 9.2 million adults in the United States have a co-occurring disorder. Co-occurring disorders may include any combination of two or more substance use disorders and mental disorders identified in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5-TR). Some of the most common mental disorders seen in SUD treatment include anxiety and mood disorders.