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Cannabis Dependence Linked to Poor Mental Health

New research shows that people with a history of dependence on cannabis are more likely to have some form of mental illness or substance abuse.

“Our findings illustrate that for many adults, a history of cannabis dependence casts a very long shadow, with a wide range of associated negative mental health outcomes,” said Dr. Esme Fuller-Thomson, professor at the University of Toronto’s Factor-Inwentash Faculty of Social Work (FIFSW) and director of the Institute for Life Course and Aging and lead author of the study.

The study compared 336 Canadians with a history of cannabis dependence to 20,441 who had never been addicted to the substance. The data was drawn from Statistics Canada’s 2012 Canadian Community Health Survey-Mental Health.

The study found that more than a quarter — 28 percent — of those with a history of cannabis dependence were still dependent on cannabis, while almost half — 47% — had some form of mental illness or substance dependence, compared to only 8 percent among those without a history of cannabis dependence.

The study also found that 74 percent of people without a history of cannabis dependence were in excellent mental health, while only 43 percent of those with a history of dependence were. To be considered in excellent mental health, subjects had to report: Almost daily happiness or life satisfaction in the past month; high levels of social and psychological well-being in the past month; and freedom from all forms of substance dependence, depressive and generalized anxiety disorder, and serious suicidal thoughts for at least the preceding full year.

Social support was strongly associated with remission from cannabis addiction and achieving excellent mental health, the study discovered.

“It is important to consider ways to best facilitate social integration and social support for clients who are recovering from cannabis addiction,” said co-author Janany Jayanthikumar, M.S.W., a graduate from the university. “Clinicians may be more effective if they expand the focus of their treatment for substance dependence to include strategies to assist clients in creating and maintaining healthy social connections.”

In addition, women with a history of cannabis dependence were more likely than men to be in remission and to have excellent mental health, the study found.

“Women may experience more acutely negative physical, mental, and social consequences of substance use than men, which may motivate them to discontinue use,” explained co-author Dr. Melissa Redmond, an assistant professor of social work at Carleton University in Ottawa, Canada. “Women may also decrease substance use during pregnancy or periods of child-rearing due to side effects and associated feelings of responsibility or guilt.”

The study also found that with each decade of aging, adults had double the likelihood of achieving both remission and excellent mental health.

“Decreases in impulsivity, increased role responsibility, awareness of the impact of drug use on health, as well as negative social consequences are thought to play a role in remission among older individuals,” said co-author Senyo Agbeyaka, M.S.W.

While the Statistics Canada survey used for the study did not gather information on what interventions, if any, those with cannabis dependence received, other research indicates that combined treatments, such as motivational enhancement therapy and cognitive behavioral therapy, are successful in reducing cannabis use, as well as dependence related symptoms, the researchers observed.

Previous research indicates that among cannabis users, dependence is high. A 2013 U.S. study found that almost one-third (31 percent) of current cannabis users were cannabis dependent.

“It is important to remember that the legalization of cannabis is not solely about a profitable new business,” warned Fuller-Thomson. “With more users and subsequently more people who are cannabis dependent, there will be very serious long-term mental health repercussions that individuals, families, and the health care systems must address.”

The study was published in the journal Advances in Preventive Medicine.

Source: University of Toronto

Cannabis Dependence Linked to Poor Mental Health

Janice Wood

Janice Wood is a long-time writer and editor who began working at a daily newspaper before graduating from college. She has worked at a variety of newspapers, magazines and websites, covering everything from aviation to finance to healthcare.

APA Reference
Wood, J. (2020). Cannabis Dependence Linked to Poor Mental Health. Psych Central. Retrieved on December 4, 2020, from
Scientifically Reviewed
Last updated: 25 Apr 2020 (Originally: 25 Apr 2020)
Last reviewed: By a member of our scientific advisory board on 25 Apr 2020
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