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Original Article
March 2001

The Genetic Epidemiology of Irrational Fears and Phobias in Men

Author Affiliations

From the Virginia Institute for Psychiatric and Behavioral Genetics (Drs Kendler, Prescott, and Neale and Mr Myers) and the Departments of Psychiatry (Drs Kendler, Prescott, and Neale and Mr Myers) and Human Genetics (Drs Kendler and Neale), Medical College of Virginia of Virginia Commonwealth University, Richmond.

Arch Gen Psychiatry. 2001;58(3):257-265. doi:10.1001/archpsyc.58.3.257

Background  Much of our knowledge of the role of genetic factors in the etiology of phobias comes from one population-based sample of female twins. We examined the sources of individual differences in the risks for phobias and their associated irrational fears in male twins.

Methods  In personal interviews with both members of 1198 male-male twin pairs (707 monozygotic [MZ] and 491 dizygotic [DZ]) ascertained from a population-based registry, we assessed the lifetime history of agoraphobia and social, animal, situational, and blood/injury phobias as well as their associated irrational fears. Twin resemblance was assessed by means of probandwise concordance, odds ratios, tetrachoric correlations, and univariate and multivariate biometrical model fitting.

Results  The suggestive results obtained by analysis of phobias only were supported by analyzing both fears and phobias. All 5 phobia subtypes aggregate within twinpairs. This aggregation is due largely or solely to genetic factors with heritability of liabilities ranging from 25% to 37%. Multivariate analysis revealed a common genetic factor, genetic factors specific to each subtype, and a common familial-environmental factor.

Conclusions  In male subjects, genetic risk factors, which are partially common across all subtypes and partially subtype specific, play a moderate role in the etiology of phobias and their associated irrational fears. Family environment probably has an impact on risk for agoraphobia and social phobia. The genetic liability to blood/injury phobias is not distinct from those of the more typical phobias.