Are psychotic-like experiences related to a discontinuation of cannabis consumption in young adults?

Impulsivity behaviors and white matter mediate the relationship between genetic risk for cannabis use disorder and early cannabis use in adolescents

BACKGROUND AND AIM

Cannabis use disorder (CUD) is strongly influenced by genetic factors; however the mechanisms underpinning this association are not well understood. This study investigated whether a polygenic risk score (PRS) based on a genome-wide association study for CUD in adults predicts cannabis use in adolescents and whether the association can be explained by inter-individual variation in structural properties of brain white matter or risk-taking behaviors.

DESIGN AND SETTING

Longitudinal and cross-sectional analyses using data from the IMAGEN cohort, a European longitudinal study integrating genetic, neuroimaging and behavioral measures. We measured associations between PRS for CUD, novelty and sensation seeking traits and fractional anisotropy (FA) of white matter tracts. Mediation modeling explored whether novelty seeking and FA mediated the association between the PRS and cannabis use.

PARTICIPANTS

Participants were assessed at 14 (n = 1762), 19 (n = 1175) and 23 (n = 1139) years old.

MEASUREMENTS

European School Survey Project on Alcohol and Other Drugs, substance use risk profile scale, Fagerstrom Test for Nicotine Dependence, temperament and character inventory, Kirby Monetary Questionnaire, diffusor tensor imaging and CUD-PRS.

FINDINGS

CUD-PRS was associated with adolescent total cannabis exposure [P < 0.001, beta = 0.098 (95% confidence interval = 0.059, 0.137)] as well as with other substance use measures [alcohol P = 0.002, beta = 0.058 (0.020, 0.096); cigarettes smoked P < 0.001, beta = 0.086 (0.044, 0.128); fargestrom score P < 0.001, beta = 0.062 (0.028, 0.096); drug score P < 0.001, beta = 0.106 (0.065, 0.147)]. CUD-PRS was also associated with impulsivity, risk-taking behaviors [impulsivity P < 0.001, beta = 0.106 (0.060, 0.142); sensation seeking P < 0.001, beta = 0.094 (0.0523, 0.1357); novelty seeking P < 0.001, beta = 0.105 (0.064, 0.146); discounting task P < 0.001, beta = 0.051 (0.013, 0.089)] and average FA [P < 0.001, beta = -0.010 (-0.015, -0.005)]. Longitudinal mediation models showed that these behaviors and brain measures could mediate the association of PRS with cannabis use [overall indirect effect for novelty seeking P < 0.001, beta = 0.048 (0.028, 0.068); impulsivity P = 0.016, beta = 0.019 (0.004, 0.035); sensation seeking P < 0.001, beta = 0.034 (0.017, 0.05)].

CONCLUSIONS

The genetic risk of adult cannabis use disorder appears to be associated with substance use behavior and white matter structure as early as age 14. The observed mediation effect is consistent with the notion that genetic risk increases novelty seeking in a way that leads to more cannabis use in adolescents.

Evidence for sex differences in the impact of cytochrome P450 genotypes on early subjective effects of cannabis

Early positive subjective effects of cannabis predict the development of cannabis use disorder (CUD). Genetic factors, such as the presence of cytochrome P450 genetic variants that are associated with reduced Δ9-tetrahydrocannabinol (THC) metabolism, may contribute to individual differences in subjective effects of cannabis. Young adults (N = 54) with CUD or a non-CUD substance use disorder (control) provided a blood sample for DNA analysis and self-reported their early (i.e., effects upon initial uses) and past-year positive and negative subjective cannabis effects. Participants were classified as slow metabolizers if they had at least one CYP2C9 or CYP3A4 allele associated with reduced activity. Though the CUD group and control group did not differ in terms of metabolizer status, slow metabolizer status was more prevalent among females in the CUD group than females in the control group. Slow metabolizers reported greater past year negative THC effects compared to normal metabolizers; however, slow metabolizer status did not predict early subjective cannabis effects (positive or negative) or past year positive effects. Post-hoc analyses suggested males who were slow metabolizers reported more negative early subjective effects of cannabis than female slow metabolizers. Other sex-by-genotype interactions were not significant. These initial findings suggest that genetic variation in CYP2C9 and CYP3A4 may have sex-specific associations with cannabis-related outcomes. Slow metabolizer genes may serve as a risk factor for CUD for females independent of subjective effects. Male slow metabolizers may instead be particularly susceptible to the negative subjective effects of cannabis.