Impulsivity, Variation in the Cannabinoid Receptor (CNR1) and Fatty Acid Amide Hydrolase (FAAH) Genes, and Marijuana-Related Problems

Abstract

Impulsivity is associated with increased marijuana use and subsequent marijuana-related problems among marijuana users. In addition, single nucleotide polymorphisms (SNPs) in the cannabinoid receptor 1 (CNR1) and fatty acid amide hydrolase (FAAH) genes have been associated with cannabis-related phenotypes. This exploratory study tested whether the association between different aspects of impulsivity and the number of marijuana-related problems among users is explicated by variation in these putative cannabinoid-related genes. A total of 151 young adult regular marijuana users (used on M= 41.4% of the prior 60 days, SD = 24.3%) provided DNA and completed measures of trait (Barratt Impulsiveness Scale) and behavioral impulsivity (Stop Signal Task and Delay Discounting Questionnaire), as well as a self-report of marijuana-related problems. Three CNR1 and five FAAH SNPs were genotyped, tested for haplotype blocks, and subsequently examined for association with phenotypes described above. CNR1 variation significantly moderated the association between trait-level, but not behavioral, impulsivity and marijuana-related problems, such that the combination of higher trait impulsivity and CNR1 variation was associated with a greater number of marijuana-related problems. In contrast, there were no significant FAAH by impulsivity interactions; however, there was a main effect of FAAH on marijuana-related problems. These findings support an association with CNR1 and FAAH genes and marijuana-related problems among regular marijuana users. CNR1 variation emerged as a moderator of the relationship between trait impulsivity and marijuana problems, thus suggesting that marijuana users with CNR1 risk variants and a higher trait impulsivity are at greater risk for developing marijuana-related problems and supporting a role for CNR1 in a broader impulsivity phenotype.