Dual Diagnosis also called co-occurring disorders, is the condition of suffering from a mental illness and a comorbid substance abuse problem. There is considerable debate surrounding the appropriateness of using a single category for a heterogeneous group of individuals with complex needs and a varied range of problems. The concept can be used broadlymor it can be restricted to specify severe mental illness and substance misuse disorder or a person who has a milder mental illness and a drug dependency. Those with co-occurring disorders face complex challenges. They have increased rates of relapse, hospitalization, homelessness, and HIV and hepatitis C infection compared to those with either mental or substance use disorders alone.