Study data published in JAMA Network Open outline longitudinal changes in suicidality and cannabis use since 2008. Over the study period, past-year suicide ideation, plan, and attempt increased significantly in prevalence, as did rates of daily cannabis use. Whether or not the increase in suicidality is directly related to increased cannabis use requires further investigation.

The number of US adults with past-year cannabis use doubled between 2008 and 2019. During the same time period, the number of adults who reported serious thoughts of suicide also increased substantially.

The relationship between these trajectories is unclear. While prior research indicates that cannabis use may increase the severity of certain psychiatric symptoms, its impact on suicidality is unknown.


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To inform this gap, investigators extracted data from the National Surveys on Drug Use and Health (NSDUH) for the years 2008 through 2019. Administered as face-to-face household interviews, the NSDUH capture substance use and psychiatric symptoms. The primary exposure was past-year cannabis use or cannabis use disorder (CUD). The outcome of interest was suicidality, defined as past-year ideation, plan, or attempt. Stratified multivariable logistic regression models were used to assess the relationship between cannabis use and suicidality. Models were adjusted for sex and prior major depressive episode (MDE), along with other clinical and sociodemographic factors.  

The study cohort comprised 281,650 adults aged 18 to 34 years at the time of survey, among whom 49.9% were men and 50.1% were women. Between 2008 and 2019, the prevalence of past-year suicidal ideation and suicide plan increased substantially in every sociodemographic group examined. After adjusting for depression status, CUD, cannabis use frequency, and additional confounders, the adjusted prevalence of suicidal ideation increased 1.4-fold between 2008 and 2019 (adjusted risk ratio [ARR], 1.4; 95% CI, 1.3-1.5).

Similarly, the ARRs for suicide plan and suicide attempt increased 1.6-fold (95% CI, 1.5-1.9) and 1.4-fold (95%, 1.2-1.7), respectively. Daily cannabis use, CUD, and nondaily use were each associated with increased risk for suicidality compared with no cannabis use, particularly among women. These associations persisted even among individuals without a prior history of MDE: the prevalence of suicidality among those with vs without CUD was 13.9% vs 3.5% in women and 9.9% vs 3.0% in men (P <.001). The prevalence of suicidality among patients with CUD and MDE was 23.7% for women and 15.6% for men (P <.001).

Results from this national survey study suggest that the prevalence of suicidality has increased over time and may be related to increased cannabis use. However, the presence of many intersecting risk factors makes the assertion of causality difficult. Further research is necessary to better illuminate the impact of cannabis use on mental health. CUD and daily cannabis use, in particular, were associated with a greater incidence of suicidality.

“The results of this survey study indicate that CUD, daily cannabis use, and even nondaily cannabis use are associated with the risks of suicidal ideation, plan, and attempt in both young adult men and women, but significantly more so in women than men,” the investigators wrote. “Future research is needed to examine the increase in suicidality and to determine whether it is cannabis use or overlapping risk factors that increase risks for both.”

Disclosure: One study author declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures. 

Reference

Han B, Compton WM, Einstein EB, Volkow ND. Associations of suicidality trends with cannabis use as a function of sex and depression status. JAMA Netw Open. Published online June 22, 2021. doi:10.1001/jamanetworkopen.2021.13025