Introduction: While many studies suggest that regular cannabis use leads to deficits in cognitive functioning, particularly in memory, few have measured effort put forth during testing, and none have examined this as a potential mediator. Both age of onset of regular cannabis use and frequency of use have been linked to increased risk of memory deficits. The present study sought to determine whether effort mediated the relationship between frequency or age of onset of cannabis use and learning and memory performance.
Method: Sixty-two participants (74% male, mean age = 19.25 years) who met criteria for chronic cannabis use (four or more days per week for at least 12 months) completed a neuropsychological battery including the California Verbal Learning Test-II (CVLT-II) and the Rey Complex Figure (RCF) as measures of learning and memory, and the Word Memory Test (WMT) as a measure of effort put forth during neuropsychological assessment.
Results: Participants who more frequently used cannabis exhibited poorer effort (as measured by WMT performance; p < .01). Bootstrapping yielded 95% confidence intervals for indirect effects and revealed that effort significantly mediated the relationship between frequency of cannabis use and CVLT-II Learning (Sum of Trials 1-5), CVLT-II Delayed Recall, and RCF Delayed Recall, but not RCF Immediate Recall. Age of onset of cannabis use was not significantly related to effort.
Conclusions: Findings indicate that effort mediates the relationship between frequency of cannabis use and performance on learning and memory measures, suggesting that effort performance should be measured and controlled for in future studies assessing cognition in frequent cannabis users.
Keywords: Cannabis; Effort; Learning; Marijuana; Memory.