In the last decade, it has become technically and economically feasible to interrogate the genome directly with increasing resolution and completeness. Instead of indirectly studying the heredity of psychiatric disorders (e.g., via studies of pedigrees, twins, or adoptees), we can now evaluate the genomes of cases and controls at several levels of precision quickly and inexpensively. Indeed, heritability itself can be assessed directly from genome-wide genetic data (7, 8).
