Editorial: Marijuana Legalization and Suicide in Adolescents and Transitional-Age Youth: Important Future Directions for This Line of Research

Medical and recreational marijuana legalization (ML) processes in the United States have been prompted by the potential for positive downstream legal effects of decriminalization, including fewer cannabis-related arrests and prosecutions, which have historically disproportionately impacted minoritized communities. However, ML evolved through primarily political processes, with minimal scientific guidance to inform policies. Unfortunately, commercialization has increased youth cannabis access, diversion of parental cannabis, and proliferation of high-potency products which, along with early use, are associated with poor mental health outcomes.¹ Taken together, these findings raise concerns about the impact of medical (MML) and recreational marijuana legalization (RML) on youth mental health.

The association between cannabis use and increased suicide risk is concerning. Cannabis use has been associated with increased suicide risk in multiple large studies conducted across countries and supported by systematic reviews and meta-analyses of existing literature in both adults and adolescents.^2–5 Additionally, one Norwegian study revealed potential sex differences, demonstrating an association between cannabis and suicide-related phenomena in female- but not male-identifying people.² Further, COVID-19 exacerbated suicide-related phenomena, especially as cannabis use increased during the pandemic.⁶ In addition, adolescent onset of cannabis use is associated with suicidal behavior both during adolescence and young adulthood.⁷ Despite all these important findings, the impact of changing marijuana laws on suicide risk, particularly during adolescence, is poorly understood.

To begin to address gaps in the child and adolescent literature, Hammond et al. examined associations between US MML and RML and suicide-related deaths using data from the National Vital Statistics System (2000–2019).⁸ Utilizing a quasi-experimental study design and staggered adoption difference-in-difference analytic approach, the authors investigated associations of state-level MML or RML with suicide rates in youth aged 12–25 years. They found that the unadjusted annual suicide rate (per 100,000) was 9.76 for states with no ML, compared to 12.77 for MML states and 16.68 for RML states. Among female-identifying youth, both MML (10% increase) and RML (16% increase) were associated with significantly higher suicide rates across all age groups, when compared to female-identifying youth in states without ML. Additionally, across female- and male-identifying youth aged 14–16 years, people in RML states were at 9 and 14% higher risk for suicide in contrast to those in states with no ML or with MML, respectively. Finally, to evaluate robustness of the findings, the authors conducted four sensitivity analyses, in which associations remained consistent. Potential explanations for these associations include alteration of use patterns and increased availability of high-potency products with legalization.⁸

These findings are important because they show potentially sex- or gender-based and age differences in the associations of suicide with ML, which have clinical and policy implications.

First, the presence of the association in female- but not male-identifying individuals (except in the 14–16-year-old group) suggests that research on sex differences in the associations between substance use and suicide risk is an important direction for future work. Sex differences are present in the epidemiology of mood disorders during adolescence, with the rates of depressive disorders beginning to differentiate by sex during pre-adolescence.⁹ Additionally, sex differences are observed in substance use disorders, including the rate of progression to problematic use (or telescoping), changes in neurocognition, brain-based responses, neuroinflammation, and motivations for use.¹⁰ Specifically, female-identifying youth more often report using cannabis to address internalizing problems (ie, depression, anxiety) and somatic symptoms (ie, nausea). They may also experience additional stigma related to use, particularly during their reproductive years, which begin may during adolescence.¹¹ Neurohormonal physiology and sex effects may inform evaluation and treatment of psychiatric and substance use disorders in youth, including vulnerable populations such as those receiving gender-affirming care.

Second, the associations in Hammond et al.⁸ between marijuana legalization and suicide rates were significant regardless of sex only for the 14–16-year age group. As the authors note, these data are consistent with existing data suggesting that onset of cannabis use prior to 16 years of age has a distinct impact on adolescent neurodevelopment and cognitive function (12). Notably, the findings presented by Hammond et al. differ from some studies that found a decrease in suicide rates in states with MML.¹³ However, variation in the period of data collection and population age may account for such differences. ML in the US has progressed at the state level over two decades, and there may also be dynamic changes in the impact of ML over this time. Similarly, the impact of substance use policies on youth is generally understudied, resulting in a paucity of knowledge regarding impact of ML across development.

Some caveats of the study are that the ML implementation has coincided with an increase in suicide rates among female-identifying individuals, which could confound the associations.¹⁴ Further, there are limitations regarding sex- and/or gender-specific conclusions since sex assigned at birth and gender identity were not both collected (a common concern in prior datasets). As a cross-sectional study, causality may not be inferred. Additionally, the study takes an ecological approach and does not examine individual-level mechanisms. Future studies examining longitudinal associations of cannabis use and suicide-related behaviors at the individual level may elucidate mechanisms which state-level variables cannot explain.

Nonetheless, the study’s findings have important clinical and policy implications. First, clinicians should engage in discussions about the effects of cannabis use during adolescence. Following implementation of ML, these discussions should include education for patients as well as for the public to address decreased perceived risk of use associated with legalization. Second, clinicians should advocate for support of research and evidence-based policies to regulate the marijuana industry to protect youth and other vulnerable populations.

In conclusion, both medical and recreational marijuana legalization are associated with an increase in suicide risk in adolescent and young adult female-identifying individuals, and in mid-adolescents regardless of sex. While ML may have positive effects, including expanded medical research and decreased criminalization, states should consider public health and regulatory policies, taking into consideration the impact of ML on vulnerable populations such as children and adolescents.

Diversity & Inclusion Statement:

One or more of the authors of this paper self-identifies as a member of one or more historically underrepresented racial and/or ethnic groups in science. One or more of the authors of this paper self-identifies as a member of one or more historically underrepresented sexual and/or gender groups in science. We actively worked to promote sex and gender balance in our author group.