Scientists Developed a Heritable Alcohol Consumption Measure That Also Correlated With Cannabis Use | Research

The takeaway

A single-factor alcohol consumption score combining four measures was 50% heritable and correlated with both nicotine and cannabis use, making it useful for gene-mapping studies.

Read this if you're interested in the genetics of addiction and how scientists measure substance use for genetic research.

50% heritable alcohol consumption factor correlated with cannabis and nicotine use

What the researchers found

Researchers developed a quantitative alcohol consumption factor score using four measures: maximum typical consumption, maximum drinks in 24 hours, frequency of 5+ drinks per day, and frequency of intoxication.

The composite score showed good psychometric properties: factor loadings of 0.60-0.90, measurement invariance across two samples and genders, and 50% heritability. Individual component measures were 34-47% heritable.

Importantly for substance use research, the alcohol factor correlated with nicotine and cannabis use measures similarly across samples and genders, supporting construct validity and suggesting shared genetic influences across substances.

The genetic variance in the composite factor accounted for a majority of the genetic variance in each individual measure, meaning the factor captured the common genetic influence underlying different aspects of alcohol consumption.

Why it matters

Better measurement tools for substance use improve the ability to identify genetic variants. The correlation with cannabis use supported the idea of shared genetic vulnerability across substances.

The numbers in context

3,787 female twins + 489 college sample. Factor loadings: 0.60-0.90. Heritability of composite score: 50%. Individual measures: 34-47% heritable. Correlated with nicotine and cannabis use.

How the study worked

Twin study using 3,787 young adult twin women and 489 men and women from a college drinking study. Factor analysis, measurement invariance testing, construct validation against tobacco/cannabis use, and genetic psychometric modeling were performed.

What this study cannot tell us

The primary sample was all female. Cross-validation with the college sample was helpful but limited in size. Cannabis use was examined as a correlate, not as the primary focus.

How to read the evidence

This is a well-designed twin study with rigorous psychometric validation, providing moderate evidence for the measure's utility and the shared genetics of substance use.

When this study was published

Published in 2009. This type of phenotype development has been essential for the GWAS era and subsequent identification of specific genetic variants.

The bigger picture

Developing reliable, heritable phenotypes is essential for gene-mapping studies. This measure has been used in subsequent GWAS and has helped identify genetic variants for alcohol consumption.

Questions still open

Can similar factor scores be developed for cannabis consumption specifically? Would the genetic overlap between alcohol and cannabis consumption measures help identify shared vulnerability genes?

Common questions

Why does an alcohol measure matter for cannabis research?

The finding that the alcohol consumption measure correlated with cannabis use suggests shared genetic vulnerability. Identifying genes through alcohol consumption measures may also reveal genes relevant to cannabis use and general addiction.

What does 50% heritable mean?

It means that about half of the variation in alcohol consumption patterns in the population can be attributed to genetic differences. The other half is due to environmental factors like peer influence, availability, and life experiences.

Read the original research

Developing a quantitative measure of alcohol consumption for genomic studies on prospective cohorts.

Journal of studies on alcohol and drugs, 70(2), 157-68

View on PubMed ↗

Citation

Agrawal, Arpana; Grant, Julia D; Littlefield, Andrew; Waldron, Mary; Pergadia, Michele L; Lynskey, Michael T; Madden, Pamela A F; Todorov, Alexandre; Trull, Timothy; Bucholz, Kathleen K; Todd, Richard D; Sher, Kenneth; Heath, Andrew C. (2009). Developing a quantitative measure of alcohol consumption for genomic studies on prospective cohorts.. Journal of studies on alcohol and drugs, 70(2), 157-68.