What question did this study set out to answer?

To examine the next-day cognitive performance and subjective effects after cannabis use in frequent users.

March 23, 2026Drug and Alcohol Dependence Reports0 citationsOpen Access

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

JMJustin Matheson CZChristina ZakalaCentre for Addiction and Mental Health SZSampson ZhaoCentre for Addiction and Mental Health

Key Points

To examine the next-day cognitive performance and subjective effects after cannabis use in frequent users.
Participants smoked a pre-rolled joint at night and were tested 12-15 hours later.
Cognitive tasks included verbal free recall and the Trail Making Test.
Blood and oral fluid samples were collected for cannabinoid concentration analysis.
A matched control group with no recent cannabis use was included for comparison.
Linear regression and Pearson correlations were used to analyze the data.
No significant differences in cognitive measures between cannabis users and controls.
Elevated subjective effects were reported in the cannabis group compared to controls.
Higher THC levels were linked to poorer verbal recall performance and slower processing speed on cognitive tests.
Correlations indicated that higher concentrations of THC and its metabolites in blood were associated with poorer performance.

Abstract

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. 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 hours 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. 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). There was no measurable next-day cognitive impairment, despite some subjective intoxication. 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. • Frequent cannabis users were tested 12-15 hours after smoking cannabis at home • There was no evidence of cognitive impairment relative to a matched control group • Subjective drug effect measures were elevated relative to the control group • Higher THC levels were associated with worse cognitive performance

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