Evidence from numerous family and twin studies indicates a shared genetic etiology between schizophrenia and bipolar disorder.[1][2] Geoffroy, Etain, and Houenou note that the largest family study available found a combined heritability for bipolar disorder and schizophrenia of approximately 60%, with environmental factors accounting for the remainder.[2] Genetic contributions to schizoaffective disorder appear to be entirely shared with those contributing to schizophrenia and mania.[1]