By Julian Santaella-Tenorio, Natalie S.Levy, Luis E.Segura, Pia M.Mauro, Silvia S.Martins

Background
Cannabis use disorder (CUD) prevalence among people reporting past-year cannabis use declined from 2002–2016. We examined whether similar reductions in CUD were observed among people reporting daily/almost daily cannabis use. We expected that CUD prevalence among people reporting daily/almost daily use would not decrease.

Methods
We used 2002–2016 National Survey on Drug Use and Health (NSDUH) data, including 22,651 individuals using cannabis 300+ days in the past year. CUD was defined using DSM-IV criteria for cannabis abuse and/or dependence. Age categories included: 12–17, 18–25, and 26 + . Annual prevalence of CUD, cannabis dependence, cannabis abuse, and each individual abuse/dependence items accounted for the complex survey design. Differences in trends over time were examined by age group.

Results
From 2002–2016, the prevalence of CUD among people reporting daily/almost daily cannabis use decreased by 26.8% in adolescents, by 29.7% in ages 18–25, and by 37.5% in ages 26 + . Prevalence of DSM-IV cannabis dependence decreased significantly among adolescents (-43.9%) and young adults (-26.8%) but remained stable in adults 26 + . Reductions in most dependence items were observed in young adults, with less consistent patterns in adolescents and adults 26 + . Prevalence of DSM-IV cannabis abuse decreased overall and for each abuse item across all age groups.

Conclusions
Contrary to expectations, CUD prevalence decreased significantly across all ages reporting daily/almost daily cannabis use between 2002–2016. Cannabis dependence prevalence decreased for adolescents and young adults and was stable only among adults ages 26+ reporting daily/almost daily cannabis use. Potential drivers of this decrease should be further explored.

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