Substance abuse and mental health disorders such as depression and anxiety are closely linked, and while some substance abuse can cause prolonged psychotic reactions, one does not directly cause the other. However: Alcohol and drugs are often used to self-medicate the symptoms of mental health problems.Mental health and substance use disorders affect people from all walks of life and all age groups. These illnesses are common, recurrent, and often serious, but they are treatable and many people do recover. Mental disorders involve changes in thinking, mood, and/or behavior. These disorders can affect how we relate to others and make choices. Reaching a level that can be formally diagnosed often depends on a reduction in a person’s ability to function as a result of the disorder.Whenever both depression and addiction are discussed together, the question of which comes first always arises. The basic disease model of addiction says that substance abuse changes the brain so drastically that it cannot regulate itself. For many, heavy substance abuse can certainly lead to depression.