Also known as: Co-occurring substance use and mental health disorders (CoSUM) COMHAD: A Comprehensive Guide to Co-Occurring Mental Health and Substance Use Difficulties When someone experiences both mental health difficulties and problematic substance use at the same time, this is known in policy and clinical practice as COMHAD (Co-occurring Mental Health, Alcohol and Drugs). COMHAD conditions are common, complex, and often severe, requiring integrated, person-centred care