No cannabis link with suicidal behaviour in those with psychiatric disorders

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McMaster University researchers have found there is no significant association between cannabis use and suicidal behaviour in people with psychiatric disorders. The study findings contrast with pre-existing data that shows the drug is linked to an increased chance of suicidal behaviour in the general population.

However, based on a small subset of participants, researchers did note the heaviness of cannabis use increased risk of suicidal behaviour in men, suggesting a closer follow-up by medical professionals of those patients.

“In what we believe to be a first, this study seeks to understand how cannabis use impacts suicide attempts in men and women with psychiatric disorders who are already at a heightened risk of attempting suicide,” said Zainab Samaan, lead author and an associate professor in the department of psychiatry and behavioural neurosciences at McMaster. “We know there is a high rate of cannabis use among this population and wanted to better understand any potential correlation to suicidal behaviour.”

Cannabis is the most commonly-used illicit substance worldwide, and its consumption is expected to increase as more jurisdictions, including Canada, legalise its recreational use.

The team of researchers, predominantly based in Hamilton, merged data collected for two studies based in Ontario. These included a prospective cohort study of opioid use disorder using structured scales to assign psychiatric diagnoses, and a case-control study on suicidal behaviour using the same diagnostic methods to reach a psychiatric diagnosis including substance use.

Data was analysed from a total of 909 psychiatric patients, including 465 men and 444 women. Among this group, 112 men and 158 women had attempted suicide. The average age was 40 years.

“While there was no clear link between cannabis and suicide attempts, our findings did show that among participants with psychiatric disorders, having a mood disorder or being a woman correlates with an increased risk of suicide attempt,” said Leen Naji, the study’s first author and a family medicine resident at McMaster. “Meanwhile, having a job is protective against suicide attempts.”

Naji said that further research is needed, considering Canada’s changing laws on cannabis use, and the Mental Health Action Plan of the World Health Organisation which has the aims to reduce the rate of suicide by 10% by 2020.

“Our study is both timely and relevant, especially in light of the impeding legalisation of recreational cannabis with an expected increase in access in Canada, and there remains uncertainty about the full effect of cannabis on those living with psychiatric disorders,” she said.

Samaan added that the study findings may serve to educate health professionals when assessing patients’ risk of suicide. She said the results also reinforce suggested benefits of supporting patients with psychiatric disorders in job placements and skills development.

Abstract
Background: Cannabis is the most commonly used illicit drug. In the general population, its use has been linked to a heightened propensity for suicidal behavior (SB). We hypothesize that this association varies in patients with psychiatric disorders. SB is known to vary by sex and therefore an investigation of cannabis’ association with SB must consider sex differences. The purpose of this study is to investigate the association between cannabis use and suicide attempts in men and women with psychiatric disorders.
Methods: We merged data collected for two studies based in Ontario, Canada (n = 985). We employed a multivariable logistic regression to assess the association between cannabis use and suicide attempts in men and women with psychiatric disorders.
Results: We analyzed data from 465 men and 444 women. Amongst these, 112 men and 158 women had attempted suicide. The average age of our participants was 40 years (standard deviation (SD) 12.4). We found no significant association between suicide attempts and cannabis use in men (odds ratio (OR) = 1.34, 95% confidence interval (CI) 0.81, 2.22, p = 0.260) or women (OR = 0.97, 95% CI 0.61, 1.54, p = 0.884). In a sensitivity analysis using a sample of patients with substance use disorder only, the heaviness of cannabis use was associated with small but significant association with SB in men (OR = 1.03, 95% CI 1.01, 1.05, p = 0.007).
Conclusion: Our findings indicate that there is no association between cannabis use and suicidal behavior in men or women with psychiatric disorders unlike what was reported for the general population, though the heaviness of cannabis use may have an effect in men. The impact of cannabis use in psychiatric disorders needs ongoing examination in light of its common use, impending legalization with expected increased access and the uncertainty about cannabis’ effects on prognosis of psychiatric disorders. In addition, research should continue to investigate modifiable risk factors of SB in this population of which cannabis is not a significant factor based on this study.

Authors
Leen Naji, Tea Rosic, Brittany Dennis, Meha Bhatt, Nitika Sanger, Jackie Hudson, Natalia Mouravska, Lehana Thabane, Zainab Samaan

McMaster University material
Biology of Sex Differences abstract


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