Author: James Anderson

Recent advances in genetic studies of alcohol use disorders PMC

AUD isn’t directly caused by genetics, but genetics may predispose you to developing AUD later in life. This risk is considered hereditary and may be passed down to you if you have a family history of AUD. Just as risk factors increase your chance of experiencing a condition, protective factors lower your risk. Other factors, such as friend groups and level of financial security, may be subject to change. Your genetics don’t only increase your risk of AUD — they may have protective elements as well. According to the DSM-5-TR, the more relatives you have living with AUD and the closer they are to you in relation, the higher your individual genetic risk becomes.

1. The Diagnostic and Statistical Manual of Mental Disorders, 5th edition, text revision (DSM-5-TR), a clinical diagnostic guidebook, indicates that AUD often runs in families at a rate of 3–4 times higher compared with the general population.
2. An additional challenge in the search for genetic variants that affectthe risk for AUDs is that there is extensive clinical heterogeneity among thosemeeting criteria.
3. While genetics can play a significant role in your overall AUD risk assessment, it isn’t the only factor that can elevate your chances of developing AUD.
4. Your genetics don’t only increase your risk of AUD — they may have protective elements as well.

NIAAA is committed to learning more about how genes affect AUD so that treatment—and prevention efforts—can continue to be developed and improved. It is now appreciated that a whole spectrum of allele frequencies andeffect sizes may play roles, from common variations with small effects throughrare variants of large effect. As whole exome and whole genome sequencingtechnologies come down in cost, they are being applied to identifying rarevariants. For studies of rare variants, families are quite valuable for sortingout true positives from the background of individual variations that we allharbor. Family, twin, and adoption studies have shown that alcoholism definitely has a genetic component.

The alcohol researchcommunity has begun to form larger consortia for meta-analyses and it is anticipatedthat with the resulting increase in sample size the number of robust associationswill increase. A second approach that will likely benefit the alcohol researchcommunity will be greater examination of pathways or gene sets. These approacheshave been quite fruitful for some studies and need to be employed in analyses ofalcohol-related traits and phenotypes. Over the next few years, we anticipate theidentification of additional common and rare variants contributing to the risk ofalcohol dependence.

Candidate gene studies of AUD and related traits

There are several other genes that have been shown to contribute to the riskof alcohol dependence as well as key endophenotypes. In most cases, studiesrecruited families having multiple members with alcohol dependence; such familiesare likely to segregate variants that affect the risk of alcohol dependence. Themost common initial approach was linkage analysis, in which markers throughout thegenome were measured to identify chromosomal regions that appeared to segregate withdisease across many families.

As larger samples areassembled and more variants analyzed, a much fuller picture of the many genesand pathways that impact risk will be discovered. Given such findings, molecular genetics studies have attempted to identify specific variation within the genome related to increased risk for AUD. Early work in the field focused on genome-wide linkage and candidate gene association studies. The former relies on family-based samples to identify regions of the genome that co-segregate with the disorder of interest. Family studies have consistently demonstrated that there is a substantialgenetic contribution to alcohol dependence. Extensive study of the alcoholmetabolizing genes has demonstrated their important role in disease risk.

In 1990, Blum et al. proposed an association between the A1 allele of the DRD2 gene and alcoholism. The DRD2 gene was the first candidate gene that showed promise of an association with alcoholism. As we have learned more about the role genes play in our health, researchers have discovered that different factors can alter the expression of our genes.

EARLY MOLECULAR GENETICS STUDIES

Additionalgenes have been identified that have expanded our understanding of the genes andpathways involved; however, the number of findings to date is modest. First and perhaps foremost, most studies ofalcohol-related phenotypes have been small – hundreds or a few thousandsamples. Most robust associations that have been reported in common disease haveemployed tens of thousands of samples and are now beginning to combine severalstudies of these magnitude into even larger meta analyses.

The sensitive mice tend to lose their inhibitions and pass out rather quickly, earning them the nickname “long sleepers.” “Short sleepers” are mice that are genetically less sensitive to alcohol. If you live in a situation of poverty, for example, or in an area with limited resources, you may be less likely to have access to quality foods, community services, or adequate healthcare. While genetics can play a significant role in your overall AUD risk assessment, it isn’t the only factor that can elevate your chances of developing AUD.

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Majority of genomic data for large alcohol consumption and AUD meta-analysis was either from UKBiobank or from Million Veterans Project. Several other cohorts from dbGAP also contributed to large sample size of alcohol consumption GWAS by Liu et al, 2019. Genome-wide data on 14,904 DSM-IV diagnosed AD individuals and 37,944 controls from 28 case/control and family-based studies were meta-analyzed for PGC’s AD GWAS.

New NIH study reveals shared genetic markers underlying substance use disorders

There are 35 different ways one could pick 3 criteria from 7 (DSM-IValcohol dependence) and 330 ways to pick 4 from 11 (DSM-5 severe AUD). Thedifficulties of genetic studies are compounded by environmental heterogeneity inaccess to alcohol and social norms related to drinking. Recent estimates indicate that 5.6% of individuals meet criteria for a past year AUD [2], resulting in significant social, economic and public health costs [3,4]. They may increase the overall risk by increasing drinking, orreduce risk by reducing drinking. Some alleles that reduce heavy drinking can,nevertheless, increase risk for disease in the subset of individuals who drinkheavily despite having them.

This article does not contain any studies with human or animal subjects performed by any of the authors. Published today in Nature Mental Health, the study was led by researchers at the Washington University in St. Louis, along with more than 150 coauthors from around the world. It was supported by the National Institute on Drug Abuse (NIDA), the National Institute on Alcohol Abuse and Alcoholism (NIAAA), the National Institute of Mental Health (NIMH), the Eunice Kennedy Shriver National Institute of Child Health and Human Development, and the National Institute on Aging. Having a close family relative, such as a parent, can account for up to 60% of your risk of developing AUD.