The effects of cannabis legalization on psychological and physical impairment in individuals who use cannabis frequently.

Hendrick T.; Hawawasam H.; Berley N.; Hopfer C.; Wall T.; Stallings M. · The International journal on drug policy · 2026

**Background & Methods** This longitudinal review examined the relationship between cannabis legalization and adverse effects in individuals with Cannabis Use Disorder (CUD), utilizing a pre-existing cohort of 364 high-risk participants and 407 siblings assessed before and after January 2014 when recreational cannabis dispensaries opened in Colorado. Participants were assessed twice before legalization and once after, with the hypothesis that those meeting DSM criteria for CUD post-2014 would show greater psychological and physical impairment due to increased THC concentration products. **Key Findings** - Contrary to the primary hypothesis, no significant mean differences in overall impairment were detected after 2014; high-risk participants with CUD actually endorsed significantly more DSM criteria before legalization than after legalization. - A small subgroup of 21.5% of high-risk participants and 20.1% of siblings demonstrated an increase in CUD criteria endorsed and experienced significantly more psychological and physical symptoms after 2014, suggesting differential vulnerability within the population. - The null findings may reflect tolerance development in chronic daily users with long-term cannabis exposure, limiting the detectable impact of increased THC potency products on this particular high-risk sample. **Dosage & Administration** Not reported. **Safety & Adverse Effects** The study focused on DSM diagnostic criteria for CUD and associated psychological and physical symptoms without specifying particular adverse effects. Increased THC potency was identified as a potential risk factor for vulnerable subgroups, though specific symptomatology was not detailed in the abstract. **Evidence Quality** This study has several limitations: (1) the pre-existing cohort design may not represent the general population, as participants were selected for high-risk status and prior SUD treatment; (2) the post-legalization assessment period appears limited to a single timepoint; (3) the authors acknowledge the need for studies in recreational and less-frequent cannabis users to generalize findings; (4) the small subgroup exhibiting increased symptoms (approximately 20%) suggests limited overall clinical impact; (5) the review design itself represents lower-level evidence compared to randomized controlled trials. The findings provide moderate-level evidence that legalization and increased THC potency may have heterogeneous effects, particularly in chronic, tolerant users.

More recent cannabis research