Cannabis Dependency Worsens Mental Health

Esme Fuller-Thomson, PhD

Individuals with a history of cannabis dependence were much less likely to have good mental health and much more likely to have some form of mental illness or substance dependence compared to those who had never been dependent on cannabis, according to recent study findings.

Esme Fuller-Thomson, PhD, and a team of Canada-based colleagues compared Canadians with a history of cannabis dependence to those who had never been addicted to the substance to identify the prevalence of risk and protective factors associated with cannabis remission, the absence of psychiatric disorders or addictions in the past year, and positive mental health.

The team found that only a minority of individuals who had a history of cannabis dependence thrived after remission. The findings suggested that outreach was warranted for the most vulnerable individuals with a history of cannabis dependence.

Fuller-Thomson, a professor at the University of Toronto’s Factor-Inwentash Faculty of Social Work, and the investigators used 2 sub-samples of data from the 2012 Canadian Community Health Survey-Mental Health data set. The first sub-sample consisted of all participants with complete data about their lifetime cannabis and past-year cannabis dependence, past-year mental illness and suicidality, and past-year positive mental health. The second sample was adults with a lifetime diagnosis of cannabis dependence.

The investigators measured 3 outcomes: freedom of cannabis dependence in the past year; the absence of psychiatric disorders based on no suicidal ideation or depressive episode, anxiety disorders, bipolar disorders, or any alcohol or drug dependence; and positive mental health. The team defined positive mental health as the absence of psychiatric disorders in the past year, emotional well-being, and social and psychological well-being.

The full sample included 20,777 individuals, while the cannabis-dependent group consisted of 336.

Overall, 72% of those with a history of cannabis dependence were in remission in the year before completing the team’s survey and 53% were free of any mental illness, suicidal thoughts, or addictions, which was dramatically lower than the 92% of those without a history of cannabis dependence (P <.001).

Less than half (43%) of respondents with a cannabis dependence were in positive mental health, which was also lower than the 74% of those without a history of dependence (P <.001).

Among those in the study, those with a history of cannabis dependence were more likely to be male compared to those without (71% vs 49%); to be white (87% vs 77%); to have ever had a major depressive episode (35% vs 11%); or to have ever had generalized anxiety disorders (27% vs 9%).

Individuals without a dependence history had nine-times the odds of absence of psychiatric disorders than those who had ever been dependent on cannabis (OR, 9.66; 95% CI, 7.75-12.04). Adults without a history of dependence also had three-times the odds of positive mental health compared to those who were cannabis dependent at 1 point in their lives (OR, 3.81; 95% CI, 3.06-4.75).

Women were twice as likely to enter remission than men (OR, 2.24; 95% CI, 1.16-4.35). Women were also more likely to be free of mental illness and have positive mental health.

The findings could help inform future outreach, targeting, and intervention in light of the increasing number of cannabis users due to legalization.

The study, “Is Recovery from Cannabis Dependence Possible? Factors that Help or Hinder Recovery in a National Sample of Canadians with a History of Cannabis Dependence,” was published online in the journal Advances in Preventive Medicine.