Molecular genetics will certainly not provide a simple, gene-based classification of psychiatric illness. However, it can be expected that establishing the relationship between genotypes and psychiatric phenotypes will inform understanding of psychiatric nosology and move psychiatry towards a diagnostic classification that is much closer to the underlying pathophysiology than are the current descriptive classifications. This may well be a relatively early and, clinically important, “pay off” from the major research investment in molecular genetic research in psychiatry.
