A new study, published in the journal Advances in Preventive Medicine, has found that those who have a history of cannabis dependence are more likely to have mental health issues or substance abuse.

Lead study author Dr. Esme Fuller-Thomas said, “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.”

Dr. Fuller-Thomson is a professor at the University of Toronto’s Factor-Inwentash Faculty of Social Work. She is also the director of the Institute for Life Course and Aging.

The study looked at more than 330 Canadians with a history of cannabis dependence and compared them to a group of more than 20,400 people who never had a history of cannabis dependence.

The researchers found that 28 percent of the participants with a history of cannabis dependence were still dependent on the drug and 47 percent of them had some form of mental health issue or substance abuse.

It has also been found that 74 percent of people with no history of cannabis dependence were in excellent mental health.

The researchers considered the participants in excellent mental health if they reported almost daily happiness, life satisfaction, and high levels of social and psychological well-being in the past month.

They also considered them in good mental health if the participants reported freedom from all forms of substance abuse, depression, anxiety disorder, and serious suicidal thoughts.

The study found that social support was strongly linked to remission from cannabis addiction and achieving good mental health.

Study co-author Janany Jayanthikumar, who is a clinical social worker, said, “It is important to consider ways to best facilitate social integration and social support for clients who are recovering from cannabis addiction.”

“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,” she added.

The study also found that women with a history of cannabis dependence were more likely to be in remission and to have good mental health than men.

Another study co-author Dr. Melissa Redmond said, “Women may experience more acutely negative physical, mental, and social consequences of substance use than men, which may motivate them to discontinue use. Women may also decrease substance use during pregnancy or periods of child-rearing due to side effects and associated feelings of responsibility or guilt.”

Previous studies have found that dependence is high among cannabis users. One American study, conducted in 2013, found that almost more than 30 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 Dr. 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 article originally appeared in Psych Central.