1(800) 615-1067Substance abuse is considered a mental disorder because it affects the way a person thinks, feels, and behaves. Substance abuse can lead to changes in brain function and structure, causing mental and physical health problems. It is classified as a mental disorder in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), a diagnostic tool used by mental health professionals to identify and treat mental health conditions. Substance abuse disorder is characterized by a pattern of substance use that causes significant impairment or distress, including problems with social, occupational, or personal functioning.