Background: Mood disorders exhibit familial transmission due to both environmental and genetic risk factors. Mood disorders are more common in women, yet the role of gender in the familial transmission of mood disorders is unclear. This study examines rates of mood disorder transmission to offspring based on the sex of affected parent, sex of offspring and role of clinical factors, such as childhood abuse history, comorbid psychiatric disorders, and traits of aggression and impulsivity.
Methods: Risk of transmission of mood disorder to offspring from females and males was compared in a sample of 272 probands with a major mood disorder using generalized estimating equations (GEE). Demographic and clinical characteristics of all male and female probands were compared. Characteristics that differed in probands were entered into the model to obtain an unbiased test of gender differences in transmission rate. Multivariate GEE models, one for male probands and one for female probands, were used to test for risk factors in transmission of mood disorder.
Results: Familial transmission rate of mood disorders from female probands was almost double that of males. There was no difference in transmission to male or female offspring. For male probands, offspring mood disorder was independently associated with earlier age of proband mood disorder onset, greater number of proband years ill, and proband history of childhood abuse. For female probands, offspring mood disorder was associated with higher aggression scores in probands.
Limitations: We did not directly interview offspring and also had limited data on psychopathology in co-parents. This is a cross-sectional study and cannot account for emergence of illness in offspring in the future.
Conclusions: The two-fold higher rate of maternal transmission of mood disorder may reflect differences in regulation of maternal and paternal transmission of mood disorder. Future studies need to determine the relative contribution of genetic and non-genetic factors and identify the factors responsible for higher rates of transmission of mood disorders by females with a mood disorder.