A Systematic Review and Meta-Analysis of Delay Discounting and Cannabis Use

Delay discounting reflects the systematic reduction in the value of a consequence by delay to delivery.Theoretical and empirical work suggests that delay discounting is a key behavioral mechanism underlyingsubstance use disorder. Existing work on cannabis use, however, is mixed with many studiesreporting null results. The purpose of this review was to provide an in-depth assessment of the associationbetween delay discounting and cannabis use. We conducted metaregression analyses to determine theomnibus correlation between delay discounting and cannabis use, and to evaluate task-based andsample-based moderators. Studies included evaluated an association between delay discounting andcannabis quantity-frequency or severity measures in human participants (27 studies, 61 effect sizes,24,782 participants). A robust variance estimation method was used to account for dependence amongeffect sizes. A significant, but small, omnibus effect was observed (r =.082) in which greater cannabisuse frequency or severity was associated with greater discounting. Incentive structure and outcome typewere each significant moderators in a multiple moderator model such that incentivized tasks correlatedwith severity measures showed stronger associations (r =.234) than hypothetical tasks correlated withquantity-frequency measures (r =.029). Comparisons to historic effect size data supported the hypothesisthat, at present, the relationship between cannabis use and delay discounting appears empiricallysmaller than for other substances. Future work should explore theoretical rationales explaining thismodest relationship involving cannabis use and delay discounting, such as reflecting the smallermagnitude of perceived long-term clinical outcomes associated with cannabis compared to othersubstances.