Co-Occurring Disorders

What is a co-occurring disorder?

Substance Use and Mental Health Disorders often co-exist. When these disorders exist at the same time a person is said to have a co-occurring disorder, also referred to as concurrent disorder, dual diagnosis, dual disorder, or co-morbidity.

The indicators for substance use and mental health problems are similar and include change in mood, behaviours and relations, declining school performance, quitting hobbies or dropping out of recreational activities. At times, problem substance use can mimic mental illness (e.g. people who chronically use marijuana can have similar symptoms to people with clinical depression).

Young people are at greater risk for substance use and mental health problems when there is serious family conflict, poor or inappropriate family management, physical or sexual abuse, or if one or both parents have a mental health or substance use problem.

What comes first, a substance use problem or the mental health concern?


This varies and may be difficult to determine. The two are often intertwined and related. Just as some mental illnesses have been seen to increase the incidence of substance use, substance use has been seen to increase the risk of experiencing mental health problems.

Most Common Co-occurring Mental Health Problems

Co-occurring disorders cover a wide range of specific disorder combinations. For youth who have substance use problems, the most common co-occurring mental health problems are:

  • Depression: Depression often precedes problem substance use. Most substances (e.g. alcohol, marijuana) that youth use to cope with depression cause greater depression with chronic use.
  • Social Anxiety: When a young person tries alcohol or other drugs, the anxiety-reducing effect of the substance can promote ongoing use.
  • Post-traumatic Stress: The incidence of post-traumatic stress is much higher when the young person has been sexually or physically abused. People experiencing post-traumatic stress often use substances to help numb painful emotions and deal with anger.
  • Conduct Disorders: This condition is highly linked with problem substance use and usually precedes it. It is also commonly associated with ADHD. Youth with conduct disorder are risk-takers and often use a gamut of substances to enjoy the excitement and rush.
  • Eating Disorders: Eating Disorders usually have their onset in adolescence. Young people with an eating disorder tend to use substances that suppress their appetite, such as nicotine, alcohol or stimulants (e.g., diet pills, caffeine pills, speed, cocaine).

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