Neuroticism, major depression and gender: a population-based twin study.
BACKGROUND
A portion of the genetic risk factors for the personality trait neuroticism (N) may also increase risk for major depression (MD). Females have both higher levels of N and higher rates of MD than males, suggesting that these traits may be more genetically correlated in females.


METHODS
Structured interviews, including a lifetime assessment for MD by DSM-III-R criteria, were administered to 863 male-male MZ (monozygotic), 649 male-male DZ (dizygotic), 506 female-female MZ, 345 female-female DZ, and 1,408 opposite-sex twin pairs. N was assessed using the short-form of the Eysenck Personality Questionnaire. A sex-limited Cholesky model was fitted which allowed us to decompose into additive genetic, common environmental, and individual-specific environmental components two main classes of correlations: within-sex between-variable and between-sex within-variable.


RESULTS
Our best-fitting model contained only additive genetic and individual-specific environmental factors for both N and MD. The within-sex genetic correlations between N and MD were estimated at +0.68 in men and +0.49 in women. This model fitted only slightly better than one in which the N-MD within-sex genetic correlation was constrained to be equal across the sexes, and estimated at +0.55. There may be sex-specific genes influencing both N and MD.


CONCLUSIONS
Our best-fitting model failed to establish a significant sex difference in the genetic correlation between N and MD. These results, as well as evidence for sex-specific genetic factors for both traits, have implications for the diagnosis, classification, and treatment of the affective disorders, and molecular genetic approaches to the study of these traits.
Fanous
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A
Department of Psychiatry, Medical College of Virginia, Virginia Commonwealth University and Virginia Institute for Psychiatric and Behavioral Genetics, Richmond, USA.
Gardner
C O
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Prescott
C A
CA
Cancro
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Kendler
K S
KS
D000328:Adult; D000368:Aged; D015897:Comorbidity; D003430:Cross-Sectional Studies; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology; D004200:Diseases in Twins / Q000453:epidemiology / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D008957:Models, Genetic; D009497:Neurotic Disorders / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology; D010555:Personality Inventory / Q000706:statistics & numerical data; D011594:Psychometrics; D012307:Risk Factors; D012737:Sex Factors; D014429:Twins, Dizygotic / Q000235:genetics / Q000523:psychology / Q000706:statistics & numerical data; D014430:Twins, Monozygotic / Q000235:genetics / Q000523:psychology / Q000706:statistics & numerical data; D014768:Virginia / Q000453:epidemiology