Secular Trends in the Familial Transmission of Alcoholism

Abstract

This is a study of the familial transmission of alcoholism in the families of 60 female and 240 male alcoholics ascertained in four psychiatric hospital units and in a local parole office. Eight hundred and thirty-one interviewed first-degree relatives and 125 spouses are included. The lifetime population prevalences of alcoholism in white males and females based on the Epidemiological Catchment Area Study in St. Louis were compared with the family rates. A semistructured comprehensive interview schedule (Home Environment and Lifetime Psychiatric Evaluation Record) was used and diagnoses made according to Feighner criteria for alcoholism. The methods of Survival Analysis established the presence of strong secular trends in the age-of-onset and lifetime prevalence of alcoholism in these families and in the general population. Accordingly, new methods for the analysis of family data that incorporate secular variation were developed. The Multifactorial Model of Disease Transmission was used to estimate familial correlations and these were parameterized by the “Tau” model of Familial Transmission. The model does not assume that all familial resemblance is due to genetic factors, but also includes the possibility of nongenetic transmission. Our analyses confirmed that more recently born cohorts of individuals had increased expected lifetime prevalences of alcoholism and decreased ages of onset, when compared with older cohorts. Separate age-of-onset distributions were required for males and females and the secular trends in age-of-onset were greatest in females. The differences between males and females were least in more recently born cohorts suggesting that sex-specific differences in the family and population distribution of alcoholism are decreasing. Sex and cohort specific transmissibilities for alcoholism were found and the age-specific transmissibilities in females (t²= 0.27–0.59) were significantly less than that for males (t²= 0.65–0.98). The transmissibilities were greatest in the youngest cohorts. The correlation between nonfamilial environmental factors common to siblings was 0.22 and a large degree of assortative mating was present (R_m=0.64). The influence of parental transmissible factors was greater than that expected for polygenic transmission, strongly suggesting the presence of intrafamilial nongenetic familial transmission between generations.