Transmission of alcohol use disorder across three generations: a Swedish National Study

Background: While risk for alcohol use disorder (AUD) is correlated in twins, siblings and parent-offspring pairs, we know little of how this syndrome is transmitted across three generations. Method: We examined 685 172 individuals born in Sweden from 1980 to 1990 with four grandparents, and both parents alive in 1980. AUD was assessed in all these individuals from nationwide medical, criminal and pharmacy registries. Results: AUD was stably transmitted across three generations. Parent-child and grandparent-grandchild tetrachoric correlations equaled +0.25 and +0.12, respectively. Grandchild AUD risk did not vary as a function of the sex of the parent or grandparent. However, from grandparents and parents, transmission to grandchildren was stronger in same-sex than opposite-sex pairs. Compared with a grandchild with unaffected parents and grandparents, risk for AUD with a grandparent but no parent affected, a parent but no grandparent affected or both affected increased approximately 70% and 3 and 4-fold, respectively. Grandchildren with ⩾2 grandparents affected had a 40% greater AUD risk than those with only one affected. Tetrachoric correlations for AUD between offspring and great-aunts/uncles, and aunts/uncles equaled +0.06 and +0.13, respectively. Conclusions: The transmission of AUD in Sweden across three generations is relatively stable. An orderly pattern of resemblance is seen with correlations declining by approximately 50% between first and second, and second and third-degree relatives. While the transmission of risk from affected male and female relatives does not differ, we find consistent evidence for greater resemblance in same-sex v. opposite-sex across generational pairs of relatives.