Untreated mental illness may repeatedly trigger relapse to substance use. Individuals with substance use disorders often also have mental health issues like depression or anxiety. Both the addiction and any underlying mental health problems need to be treated simultaneously through dual disorder treatment. If left untreated, mental illness symptoms could repeatedly cause people to relapse into substance abuse. Effective treatment involves medication-assisted treatment for addiction along with psychotherapy to develop healthy coping skills and address any mental health conditions that may have contributed to substance use.