Genetic Influences on Use and Abuse of Alcohol: A Study of 5638 Adult Finnish Twin Brothers

TLDR

The study’s alcohol consumption measures—frequency, quantity, and density—are highly intercorrelated, stable, and align with national sales data. The authors aimed to assess genetic contributions to alcohol use and abuse by comparing questionnaire‑based drinking metrics among 879 monozygotic and 1940 dizygotic twin brothers aged 24–49. They modeled each twin’s drinking as a function of the other twin’s consumption, age, zygosity, cohabitation status, and social contact using hierarchical linear regressions on a double‑entry data matrix. The study found no genetic influence on alcohol‑induced passouts, but significant heritability (36–40%) for frequency, quantity, and density of drinking, with greater similarity among twins in frequent social contact that persisted after controlling for age and contact.

Abstract

To evaluate genetic influences on the use and abuse of alcohol, we compared questionnaire measures of the frequency, quantity, and density of social drinking, and the frequency of alcohol-induced passouts self-reported by 879 monozygotic (MZ) and 1940 dizygotic (DZ) pairs of twin brothers, aged 24-49 yr. The measures of frequency, quantity, and density (heavy drinking once or more a month) significantly intercorrelate, and the self-reported alcohol consumption by this sample is satisfactorily stable and consistent with nationwide sales figures. None of the drinking measures was associated with twin type (zygosity), and only density correlated with age. Similarity of drinking habits among twin brothers was evaluated as a function of their genetic resemblance and age, the frequency of their social contact with one another, and the interactions of these terms. The effects were estimated from hierarchical linear regressions of a double-entry data matrix from which each twin's drinking was predicted from that of his twin brother, and that pair's age, zygosity, cohabitation status, and frequency of social contact. Significant genetic variance was found for each of the drinking measures with heritability estimates ranging from 0.36 to 0.40. Co-twins in more frequent social contact with one another reported greater similarity in their use of alcohol, but heritable variance remained after the effects of age and social contact were removed from both mean levels and co-twin resemblance. Reported frequency of passouts yielded significant, but equivalent, correlations in both MZ and DZ twins and no evidence of genetic influence.