One Month of Cannabis Abstinence in Adolescents and Young Adults Is Associated With Improved Memory

Abstract

<div class="section"> <a class="named-anchor" id="S1"> <!-- named anchor --> </a> <h5 class="section-title" id="d2219480e212">Objective:</h5> <p id="P2">Associations between adolescent cannabis use and poor neurocognitive functioning have been reported from cross-sectional studies that cannot determine causality. Prospective designs can assess whether extended cannabis abstinence has a beneficial effect on cognition. </p> </div><div class="section"> <a class="named-anchor" id="S2"> <!-- named anchor --> </a> <h5 class="section-title" id="d2219480e217">Methods:</h5> <p id="P3">Eighty-eight older adolescents who used cannabis regularly were enrolled in the hospital laboratory and a local high school between July 2015 and December 2016. Participants were randomly assigned to four weeks of cannabis abstinence, verified by decreasing 11-nor-9-carboxy-Δ9-tetrahydrocannabinol urine concentration (MJ-Abst; n=62), or a monitoring control condition with no abstinence requirement (MJ-Mon; n=26). Attention and memory were assessed at baseline and weekly for four weeks with the Cambridge Neuropsychological Test Automated Battery. </p> </div><div class="section"> <a class="named-anchor" id="S3"> <!-- named anchor --> </a> <h5 class="section-title" id="d2219480e222">Results:</h5> <p id="P4">Among MJ-Abst, 55 (88.7%) met <i>a priori</i> criteria for biochemically-confirmed 30-day continuous abstinence. There was an effect of abstinence on verbal memory, p=0.002, that was consistent across four weeks of abstinence, with no time by abstinence interaction, driven by improved verbal learning in the first week of abstinence. MJ-Abst had better memory on average and at weeks 1, 2, 3 than MJ-Mon, and only MJ-Abst improved in memory from baseline to week 1. There was no effect of abstinence on attention: both groups improved similarly, consistent with a practice effect. </p> </div><div class="section"> <a class="named-anchor" id="S4"> <!-- named anchor --> </a> <h5 class="section-title" id="d2219480e230">Conclusions:</h5> <p id="P5">This study suggests that cannabis abstinence is associated with improvements in verbal learning that appear to occur largely in the first week following last use. Future studies are needed to determine whether the improvement in cognition with abstinence is associated with improvement in academic and other functional outcomes. </p> </div>