Urine THC Levels Dropped About 50% in People Who Self-Reported Reducing Cannabis Use

Participants self-reporting cannabis use reduction had significantly lower urinary cannabinoids compared to non-reducers (difference of 391 ng/ml, 95% CI 231-551, p < 0.001). Average urinary cannabinoids decreased by up to 50% from baseline in the reduction group. However, no reliable individual-level cut-point could be established for creatinine-normalized THC.

Aggregated analysis of 7 CUD treatment trials (n=471 non-abstinent participants). Reduction defined as 50% decrease in frequency and/or 75% decrease in amount. Longitudinal models compared urinary cannabinoids between self-reported reducers (n=220) and non-reducers (n=251), controlling for parent study, study week, baseline levels, and covariates.

Cannabis harm reduction research has lacked a biochemical verification method for use reduction (unlike abstinence, which can be verified). This study takes the first step toward establishing that self-reported reduction correlates with measurable decreases in urinary THC.

The inability to biochemically verify cannabis reduction at the individual level is a major gap in harm reduction research. While this study shows group-level verification works, individual verification will require further development, possibly with more frequent or standardized sampling.

Aggregated data from different trials with varying designs and populations. Cannabis reduction was self-reported with potential bias. Creatinine normalization may not adequately account for hydration variation. 51% of original participants met criteria for analysis.