Cognitive performance and subjective effects the morning after last use of smoked cannabis by adults who use cannabis frequently: An observational study.

OBJECTIVES

To examine next-day cognitive performance and subjective drug effects after smoking cannabis and to assess associations between performance and cannabinoid concentrations in blood and oral fluid.

METHODS

In this observational study, healthy adults who regularly used cannabis (mean age 30 years; n = 65) smoked a legally purchased pre-rolled "joint" at night and were tested the next day, 12-15 h later. Healthy adults with no past-month cannabis use served as a matched control group (mean age 30; n = 65). Participants completed cognitive tasks (verbal free recall [VFR], Trail Making Test [TMT]), subjective effects questionnaires (including visual analogue scales [VAS]), and provided blood and oral fluid samples for quantification of delta-9-tetrahydrocannabinol (THC), cannabidiol (CBD), and metabolites. Linear regression models compared groups across cognitive/subjective outcomes, while Pearson correlations assessed associations between cannabinoid concentrations and performance.

RESULTS

There were no significant group differences on any cognitive measure. The cannabis group had significantly elevated VAS ratings (e.g., feeling a drug effect, Δmean=12.54, p < 0.01) compared to controls. Within the cannabis group, smoking infused (higher-THC-content) "joints" and higher %THC cannabis were associated with poorer verbal recall performance (e.g., %THC correlated with delayed verbal recall, r = -0.36, p < 0.01). Higher blood THC and THC-COOH concentrations correlated with poorer VFR and slower TMT performance, whereas blood 11-OH-THC and oral fluid THC correlated with TMT performance only (all p ≤ 0.03).

CONCLUSIONS

There was no measurable next-day cognitive differences between groups, despite some subjective intoxication in the cannabis group. Nonetheless, higher THC potency and elevated cannabinoid concentrations were associated with poorer verbal memory and processing speed, suggesting potential next-day impairment with high-THC products.