Dual diagnosis occurs when someone has both a mental disorder and an alcohol or drug problem. These conditions occur together frequently. In particular, alcohol and drug problems tend to occur with Depression Anxiety disorders Schizophrenia Personality disorders Sometimes the mental problem occurs first. This can lead people to use alcohol or drugs that make them feel better temporarily. Sometimes the substance abuse occurs first. Over time, that can lead to emotional and mental problems. To get better, someone with a dual diagnosis must treat both conditions. First, the person must go for a period of time without using alcohol or drugs. This is called detoxification. The next step is rehabilitation for the substance problem and treatment for the mental disorder. This step might include medicines, support groups and talk therapy.