Heritability of Schizophrenia and Schizophrenia Spectrum Based on the Nationwide Danish Twin Register.
Level 3 - non-randomized controlled study
Nationwide registry-based twin cohort study
PubMed 28987712 · doi:10.1016/j.biopsych.2017.08.017
What was done
Researchers linked the Danish Twin Register with the Danish Psychiatric Research Register to evaluate twins born between 1951 and 2000 (N = 31,524 twin pairs) followed through June 1, 2011. They applied liability threshold models adjusted for censoring using inverse probability weighting to estimate probandwise concordance rates and heritability for schizophrenia and schizophrenia spectrum disorders.
What was found
The probandwise concordance rate for schizophrenia was 33% in monozygotic twins compared to 7% in dizygotic twins. The estimated heritability of schizophrenia was 79%. When the outcome was expanded to schizophrenia spectrum disorders, the estimated heritability was 73%.
Why it matters
Using a nationwide cohort and statistical methods adjusting for censoring, this study confirms high genetic risk (~73% to 79%) for schizophrenia and spectrum disorders, while a 33% monozygotic concordance rate underscores the substantial role of non-genetic factors.
Limits
The analysis is restricted to the Danish population and relies on register-recorded psychiatric diagnoses without capturing undiagnosed community cases. Confidence intervals, specific environmental exposures, and exact twin zygosity breakdown are not reported in the abstract.
Cited by
- supports If one identical twin has schizophrenia, there is approximately a 50% chance that the other twin will also develop it, compared to a general population base rate of 1%.