Concurrent Disorders are when a person suffers from a substance use disorder as well as a mental health disorder. For example: an anxiety disorder and alcohol dependence, or depression and heroin dependence. Concurrent Disorders are very common and are becoming more the norm than the exception.
There has been a lot of discussion around the causes of Concurrent Disorders. Some hypothesize that Concurrent Disorders are simply people self-medicating. Others think that substance use disorder can lead to mental health disorders. A third theory is that an external event (i.e. trauma) causes both the mental health and substance use issues.
In the past, there has been trouble with treating Concurrent Disorders because addictions counsellors were insisting clients work on their mental health issues before being seen and vice versa. Recently, there has been a move towards treating both issues at the same time, preferrably by a team of counsellors.