Heritability for schizophrenia was 64%, somewhat lower than a meta-analysis of twin studies that found a heritability of 81%28. Further, the heritability for bipolar disorder was estimated at 59%, again lower than previous estimates based on twins of around 80%16. A disadvantage of twin studies is that they have relatively low power to estimate heritability for rare diseases. At the same time, they are less sensitive to age and nonadditive genetic effects than family studies. Regardless, both types of studies clearly show that both schizophrenia and bipolar disease are substantially heritable with heritabilities explaining somewhere between 60–80% of the liabilities.
