Pooled Human THC Experiments Found Stronger Tolerance Evidence for Subjective Effects Than Memory
A pooled analysis of four human THC experiments found that cannabis-use frequency moderated several subjective effects, while evidence for moderation of memory impairment was weak. Trait schizotypy did not moderate the measured acute psychosis-like response.
Individual data from controlled studies were combined
The mega-analysis included 128 cannabis users from double-blind, randomized, placebo-controlled crossover experiments. Models examined whether use frequency and schizotypal traits modified the THC-versus-placebo effect. Frequency was an existing participant characteristic, rather than a randomly assigned history of cannabis consumption.
Tolerance was domain-specific
More frequent use was associated with less change in alertness, feeling stoned and psychosis-like effects. The authors found only partial tolerance to feeling stoned and weaker evidence for memory tolerance. Reduced subjective intensity therefore did not establish equivalent protection across cognitive functions.
The trait finding was specifically null
Trait schizotypy did not moderate THC-related psychosis-like effects in this analysis. That does not show that every vulnerability measure is irrelevant or that no participant experienced adverse effects. A moderator analysis asks whether effect size varies with the measured trait under the studied conditions.
The findings help distinguish perceived intoxication from memory performance and measured psychosis-like symptoms. They do not establish that frequent users are unimpaired, or supply a personal threshold for safe activity. The pooled design improves the comparison without turning use frequency into a complete causal explanation.
Related: interpreting cannabis tolerance claims.
Research cited
Freeman AM; Mokrysz C; Hindocha C; Lawn W; Morgan CJ; Freeman TP; Saunders R; Curran HV. Does variation in trait schizotypy and frequency of cannabis use influence the acute subjective, cognitive and psychotomimetic effects of delta-9-tetrahydrocannabinol? A mega-analysis. Journal of psychopharmacology (Oxford, England) (2021). doi:10.1177/0269881120959601. Findings discussed from the study abstract.
