Clearing the air: Heightened perception of harm from secondhand cannabis smoke exposure is associated with no in-home cannabis smoking in a 21-country convenience sample.

Objective: As countries adopt more lenient cannabis use policies, perception of harm from secondhand cannabis smoke (SHCS) exposure is decreasing and most cannabis smoking is taking place at home. We quantified the relationship of reported in-home cannabis smoking with perceived harm from SHCS exposure.

Methods: The analytic sample comprised 28,154 adult respondents, from 21 countries, to the annual cross-sectional Global Drug Survey (2021) of users of licit or illicit drugs. Respondents reported perception of harm to non-smoking residents from SHCS exposure and past 30-day cannabis smoking in the home by anyone. Logistic regression estimated covariate-adjusted odds ratios and 95 % confidence intervals of in-home cannabis smoking (yes/no). The association between harm perception and in-home cannabis smoking by country of residence was also quantified.

Results: Sixty-one percent reported no in-home cannabis smoking in the last 30 days; mean perception of harm of SHCS exposure on a 10-point scale was 5.2. Those at the 75th (vs 25th) percentile of perceived harm had 70 % higher odds (OR = 1.7, 95 % CI = 1.6-1.8) of no in-home cannabis smoking. In all countries of residence, higher perception of harm was associated with reporting no in-home cannabis smoking, although not all were statistically significant. The strongest association was seen in Sweden (OR = 3.9, 95 % CI = 1.5-11.9) and New Zealand (OR = 2.3, 95 % CI = 2.0-2.7).

Conclusions: Respondents who perceived SHCS as harmful were less likely to report in-home cannabis smoking. If this association subsequently proves causal, increasing awareness of the harms associated with SHCS exposure could substantially reduce residential cannabis secondhand smoke exposure.