Disproportionate increase in cannabis use among people with serious psychological distress and associations with psychiatric service use in the United States, 2009-2019.

Background: Cannabis use is on the rise, but it is unclear how use is changing among individuals with serious psychological distress (SPD) compared to the general population as well as what associations this may have with mental health service use.

Methods: Retrospective cohort study using the National Survey on Drug Use and Health (NSDUH) 2009-19 public use files of 447,228 adults aged ≥ 18 years. Multivariable logistic regression and predictive margin methods were used to estimate linear time trends in any and greater-than-weekly levels of cannabis use by year and SPD status and rates of psychiatric hospitalization and outpatient mental health care.

Findings: Rates of any and weekly-plus cannabis use increased similarly among individuals with SPD compared to those without from 200 to 2014 but more rapidly in SPD every year from 2015 to 2019 (p < 0.001). Among individuals with SPD, no use was associated with a 4.2 % probability of psychiatric hospitalization, significantly less than less-than-weekly (5.0 %, p = 0.037) and weekly-plus cannabis use (5.1 %, p = 0.028). For outpatient mental health care, no use was associated with a 27.4 % probability (95 % CI 26.7-28.1 %) of any outpatient care, significantly less than less than weekly use (32.6 % probability, p < 0.001) and weekly-plus use (29.9 % probability, p = 0.01).

Conclusions: Cannabis use is increasing more rapidly among individuals with SPD than the general population, and is associated with increased rates of psychiatric hospitalization and outpatient service use. These findings can inform policy makers looking to tailor regulations on advertising for cannabis and develop public health messaging on cannabis use by people with mental illness.