Association of Cannabis Use With Self-harm and Mortality Risk Among Youths With Mood Disorders.

Importance: Cannabis use and cannabis use disorder (CUD) are common among youths and young adults with mood disorders, but the association of CUD with self-harm, suicide, and overall mortality risk is poorly understood in this already vulnerable population. Objective: To examine associations of CUD with self-harm, suicide, and overall mortality risk in youths with mood disorders. Design, Setting, and Participants: A population-based retrospective cohort study was performed using Ohio Medicaid claims data linked with death certificate data. The analysis included 204 780 youths (aged 10-24 years) with a diagnosis of mood disorders between July 1, 2010, and December 31, 2017, who were followed up to 365 days from the index diagnostic claim until the end of enrollment, the self-harm event, or death. Statistical analysis was performed from April 4 to July 17, 2020. Exposure: Physician-diagnosed CUD defined using outpatient and inpatient claims from 180 days prior to the index mood disorder diagnostic claim through the 365-day follow-up period. Main Outcomes and Measures: Nonfatal self-harm, all-cause mortality, and deaths by suicide, unintentional overdose, motor vehicle crashes, and homicide. Marginal structural models using inverse probability weights examined associations between CUD and outcomes. Results: This study included 204 780 youths (133 081 female participants [65.0%]; mean [SD] age at the time of mood disorder diagnosis, 17.2 [4.10] years). Cannabis use disorder was documented for 10.3% of youths with mood disorders (n = 21 040) and was significantly associated with older age (14-18 years vs 10-13 years: adjusted risk ratio [ARR], 9.35; 95% CI, 8.57-10.19; and 19-24 years vs 10-13 years: ARR, 11.22; 95% CI, 10.27-12.26), male sex (ARR, 1.79; 95% CI, 1.74-1.84), Black race (ARR, 1.39; 95% CI, 1.35-1.44), bipolar or other mood disorders (bipolar disorders: ARR, 1.24; 95% CI, 1.21-1.29; other mood disorders: ARR, 1.20; 95% CI, 1.15-1.25), prior history of self-harm (ARR, 1.66; 95% CI, 1.52-1.82), previous mental health outpatient visits (ARR, 1.26; 95% CI, 1.22-1.30), psychiatric hospitalizations (ARR, 1.66; 95% CI, 1.57-1.76), and mental health emergency department visits (ARR, 1.54; 95% CI, 1.47-1.61). Cannabis use disorder was significantly associated with nonfatal self-harm (adjusted hazard ratio [AHR], 3.28; 95% CI, 2.55-4.22) and all-cause mortality (AHR, 1.59; 95% CI, 1.13-2.24), including death by unintentional overdose (AHR, 2.40; 95% CI, 1.39-4.16) and homicide (AHR, 3.23; 95% CI, 1.22-8.59). Although CUD was associated with suicide in the unadjusted model, it was not significantly associated in adjusted models. Conclusions and Relevance: Cannabis use disorder is a common comorbidity and risk marker for self-harm, all-cause mortality, and death by unintentional overdose and homicide among youths with mood disorders. These findings should be considered as states contemplate legalizing medical and recreational marijuana, both of which are associated with increased CUD.

Traffic fatalities within US states that have legalized recreational cannabis sales and their neighbours.

BACKGROUND AND AIMS: A growing body of evidence suggests that cannabis impairs driving ability. We used mortality data to investigate whether the commercial sale of cannabis for recreational use affected traffic fatality rates both in states that legalized it and in neighbouring jurisdictions. DESIGN: Interrupted time-series of traffic fatality rates adjusted for seasonality and autocorrelation. Changes are reported as step and trend effects against a comparator of states that had not implemented medicinal or recreational cannabis during the study period (2009-16). Sensitivity analyses added a 6-month 'phase-in' to account for lags in production. Meta-analyses were used to derive pooled results. SETTING: Three states that legalized recreational cannabis sales [Colorado (January 2014), Washington State (June 2014) and Oregon (October 2015] and nine neighbouring jurisdictions [Kansas, Nebraska, New Mexico, Oklahoma and Utah (Colorado neighbours); British Columbia and Oregon (Washington neighbours); and California and Nevada (Oregon neighbours)]. MEASUREMENTS: Monthly traffic fatalities rates per million residents using mortality data from CDC WONDER and RoadSafetyBC and census data. FINDINGS: There was a pooled step increase of 1.08 traffic fatalities per million residents followed by a trend reduction of -0.06 per month (both P < 0.001), although with significant heterogeneity between sites (step: I2  = 73.7%, P < 0.001; trend: I2  = 68.4%; P = 0.001). Effects were similar in both legalizing (step: 0.90, P < 0.001; trend: -0.05, P = 0.007) and neighbouring sites (step: 1.15, P = 0.005; trend: -0.06, P = 0.001). The 6-month phase-in produced similar if larger effects (step: 1.36, P = 0.006; trend: -0.07, P < 0.001). CONCLUSIONS: The combination of step increases and trend reductions suggests that in the year following implementation of recreational cannabis sales, traffic fatalities temporarily increased by an average of one additional traffic fatality per million residents in both legalizing US states of Colorado, Washington and Oregon and in their neighbouring jurisdictions.