Abstract

Non-acute effects of cannabis on neurocognition in adolescents remain unclear with most studies being cross-sectional. Therefore, the aim of this longitudinal, multi-center study was to examine the effects of cannabis use on cognitive abilities in participants emerging into adulthood.
Data on substance use as well as neurocognitive measures were assessed in 804 adolescents (441 females, 363 males) at age 14 and 19. First, cross-sectional analyses of baseline and follow- up data were conducted using analyses of covariance (ANCOVA). Second, repeated measures ANCOVAs were conducted to quantify longitudinal change.
Cross-sectionally, we detected no significant neurocognitive differences before initiation of drug use. However, after controlling for confounders, light cannabis use as well as late-onset thereof was associated with increased decision-making skills both cross-sectionally at follow-up as well as longitudinally compared to non-using controls.
In summary, our data suggests that decision-making is not impaired when cannabis is used in moderation and onset of use occurs after the age of 15. In addition, we find no evidence to support the presumption that cannabis consumption leads to a decline in neurocognitive ability.