Psychopathology and treatment of 30,344 twins in Sweden. II. Heritability estimates of psychiatric diagnosis and treatment in 12,884 twin pairs.

We estimated the heritability for inpatient psychiatric treatment, treatment with psychoactive medication, and for psychiatric diagnoses in a randomized sample of 12,884 Swedish twin pairs drawn from the general population for a health survey. We found a genetic contribution to treatment and diagnosis, independent of sex and shared environment. The heritability estimate for inpatient treatment was 0.47, for reported treatment with psychoactive medication 0.49, and for an inpatient diagnosis of neurotic or personality disorder 0.60. No statistically significant heritability was found for the diagnoses of alcohol abuse nor for the heterogeneous group of diagnoses of psychoses. This was probably because of the heterogeneity of cases necessary to form large enough groups for analysis, or ascertainment requiring treatment in a psychiatric unit.