A specific gene variant in the cannabinoid receptor gene was linked to more frequent cannabis use around age 18

Latent growth curve modeling of 10 longitudinal waves spanning ages 18.4 to 23.8 years in 334 non-Hispanic White participants. Eight independent SNPs in or near the CNR1 gene were tested for association with both level and growth of cannabis use. Peer drug use was included as a time-varying predictor and potential moderator. Corrections for multiple comparisons were applied.

This study pinpoints a developmental window (around age 18) when a specific genetic variant influences cannabis use frequency. The fact that the genetic effect was limited to initial level, not trajectory, suggests that genetic vulnerability to cannabis may operate primarily during the transition out of high school, after which environmental factors like peer influence become more important.

Genetics and environment do not simply add up; they operate in developmental windows. This finding that a cannabinoid receptor gene variant matters most around age 18 suggests that genetic vulnerability to cannabis may be particularly relevant during specific life transitions, which could help target prevention efforts.

Small sample size (334 participants) limits statistical power. Restricted to non-Hispanic White individuals, so findings may not generalize to other populations. Only one of eight tested SNPs was significant, and the effect was modest. Self-reported cannabis use may be inaccurate.