What are concurrent disorders?

From Chapter 1: Introduction in Improving our Response to Older Adults with Substance Use, Mental Health and Gambling Problems: A Guide for Supervisors, Managers and Clinical Staff

A person can be said to have concurrent disorders when he or she has both a substance use and a mental health problem.

The term concurrent disorders is used in Ontario; elsewhere, such as in British Columbia and the United States, other terms are used, including co-morbid or co-occurring disorders, complicated chemical dependency and dual diagnosis (in Ontario dual diagnosis refers to co-occurring developmental delay and mental health problems).

Concurrent disorders vary in severity and in type and include people with:

significant but milder mental health and substance use problems
substance-induced or exacerbated psychiatric disorders
severe and persistent substance use and mental health problems.

The most common combination of concurrent disorders is co-occurring substance use and mood and anxiety disorders. Following that, in order of occurrence, is co-occurring substance use and severe and persistent mental disorders (e.g., schizophrenia), personality disorders and eating disorders (Health Canada, 2001).

When working with people with either a mental health or substance use problem, concurrent disorders should be considered “an expectation, not an exception” (Minkoff, 2000). Many, if not most people receiving services for a mental health or substance use disorder have concurrent disorders.

The relationship between substance use and mental health problems

The relationship between substance use and mental health problems differs from person to person. It is not always possible to understand which came first. However, it is important to understand that the two problems often influence and affect one another. For example:

People with mental health problems are more vulnerable to substance use problems. They tend to develop problems at lower levels of substance use and may use substances to attempt to relieve their psychiatric symptoms.
Substance use can induce psychiatric symptoms. Alcohol, for example, when used heavily over a period of time can cause symptoms of depression. Substance use can also lead to psychosocial problems that may in turn lead to mental health problems.
A common genetic, developmental or environmental factor could trigger both problems. A traumatic event, for example, such as a sexual assault, could lead to both mental health and substance use problems.
Mental health and substance use problems may not interact: even when one is under control, the other may still be active (O’Grady & Skinner, 2007).