The insights from GWAS specific to psychiatric disorders are similar, but they include some additional interesting observations, suggesting new ways to look at GWAS data. One is the possible involvement of rare copy number variations in schizophrenia and autism, a possibility that has received substantial support (26–37). Another is the possible involvement of thousands of genes with very small effects in schizophrenia, genes that overlap significantly with those involved in other psychiatric disorders like bipolar disorder (38). As shown in the paper from the International Schizophrenia Consortium (38), a risk score can be generated from multiple variants with weak associations with schizophrenia (certainly including many false positives), and such a score will differ when comparing controls to schizophrenic or bipolar patients, but not to patients with non-psychiatric disorders. Although, once again, the explained variance from such a score was small the approach provides a glimpse of the power that genetics will have when such groups of variants become free of false positives and of how dissecting such groups of variants/genes will help us understand how different disorders both overlap and differ.
