Genetic and environmental etiology of drinking motives in college students

Drinking motives and alcohol sensitivity mediate multi-dimensional genetic influences on alcohol use behaviors

Background

Genetic influences account for a substantial proportion of individual differences in alcohol use behaviors (AUBs). However, multiple distinct sets of genes are linked to different AUBs, which may explain their dramatic variability in risk factors and manifestations. In this study, we explore whether intermediate neurobiological traits and alcohol-related cognitions mediate the relationship between polygenic scores (PGS) and multiple AUBs, with the aim to better understand processes captured by different genetic profiles.

Methods

Using results from prior genome-wide association studies, we derived PGS for 6 AUBs in participants from Spit for Science, a longitudinal study of college students in the U.S. (n=4,549). Self-report measures included personality traits, alcohol expectancies, drinking motivations, and alcohol sensitivity measures as well as drinking frequency, drinking quantity, alcohol use disorder (AUD) symptoms, and maximum drinks in 24 hours. Using linear regression and multiple mediation models, we investigated the direct and indirect effects of PGS on AUBs.

Results

In univariable regression results, PGSs indexing broad AUB dimensions such as drinks per week (DPW) and AUD predicted higher levels of sensation-seeking and multiple drinking motives, while BeerPref PGSs (indexing a variable pattern of alcohol problems associated with a preference for beer) predicted higher negative urgency and lower alcohol sensitivity. Mediational models indicated strong direct and indirect effects of DPW PGSs on multiple AUBs via social/enhancement drinking motives and alcohol sensitivity, indirect effects of AUD PGSs on AUD symptoms via coping motives, and indirect effects of BeerPref PGS on all AUBs via the joint effect of mediators including alcohol sensitivity.

Conclusions

These findings provide initial evidence that the genetic influences on different AUBs are associated with and partially mediated by intermediate neurobiological and cognitive factors, which may be more amenable to intervention. Greater focus on drinking motives and alcohol sensitivity is warranted in genetic research, as well as attention to the heterogeneous pathways linking genes to alcohol use outcomes.

Randomized Placebo-Controlled Clinical Trial of Dutasteride for Reducing Heavy Drinking in Men

BACKGROUND

Prior studies indicate that neuroactive steroids mediate some of alcohol's effects. Dutasteride, widely used to treat benign prostatic hypertrophy, is an inhibitor of 5-alpha reductase enzymes, which play a central role in the production of 5α-reduced neuroactive steroids. The purpose of this study was to test dutasteride's tolerability and efficacy for reducing drinking.

METHODS

Men (n = 142) with heavy drinking (>24 drinks per week) and a goal to either stop or reduce drinking to nonhazardous levels were randomized to placebo or 1 mg dutasteride daily for 12 weeks. We hypothesized that dutasteride-treated patients would be more successful in reducing drinking.

RESULTS

Generalized linear mixed models that included baseline drinking, treatment, time and their 2-way interaction identified significant interactions of treatment-time, such that dutasteride treatment reduced drinking more than placebo. During the last month of treatment, 25% of dutasteride-treated participants had no hazardous drinking (no heavy drinking days and not more than 14 drinks per week) compared with 6% of placebo-treated participants (P = 0.006; NNT = 6). Sensitivity analysis identified baseline drinking to cope as a factor associated with larger reductions in drinking for dutasteride compared with placebo-treated participants. Dutasteride was well tolerated. Adverse events more common in the dutasteride group were stomach discomfort and reduced libido.

CONCLUSION

Dutasteride 1 mg daily was efficacious in reducing the number of heavy drinking days and drinks per week in treatment-seeking men. The benefit of dutasteride compared with placebo was greatest for participants with elevated baseline drinking to cope motives.

Genetic and environmental etiology of drinking motives in college students

BACKGROUND

Drinking motives are robust proximal predictors of alcohol use behaviors and may mediate distinct etiological pathways in the development of alcohol misuse. However, little is known about the genetic and environmental etiology of drinking motives themselves and their potential utility as endophenotypes.

METHODS

Here, we leverage a longitudinal study of college students from diverse racial/ethnic backgrounds (phenotypic N = 9889, genotypic N = 4855) to investigate the temporal stability and demographic and environmental predictors of four types of drinking motives (enhancement, social, coping, and conformity). Using genome-wide association study (GWAS) and in silico tools, we characterize their associated genes and genetic variants (single nucleotide polymorphisms or SNPs).

RESULTS

Drinking motives were stable across four years of college (ICC >0.74). Some robust environmental predictors of alcohol misuse (parental autonomy granting and peer deviance) were broadly associated with multiple types of drinking motives, while others (e.g., trauma exposure) were type specific. Genome-wide analyses indicated modest SNP-based heritability (14-22%, n.s.) and several suggestive genomic loci that corroborate findings from previous molecular genetic studies (e.g., PECR and SIRT4 genes), indicating possible differences in the genetic etiology of positive versus negative reinforcement drinking motives that align with an internalizing/externalizing typology of alcohol misuse. Coping motives were significantly genetically correlated with alcohol use disorder diagnoses (r_g  = 0.71, p = 0.001). However, results from the genetic analyses were largely underpowered to detect significant associations.

CONCLUSIONS

Drinking motives show promise as endophenotypes but require further investigation in larger samples to further our understanding of the etiology of alcohol misuse.