What distinguishes DSM-5 from the previous editions of the Diagnostic and Statistical Manual?

Darrel Regier: As the Task Force began to meet in preparation for working on DSM-5, the main question we considered was whether the old psychiatric diagnostic category system embodied in DSM-IV was actually starting to hinder research by failing to reflect the latest science about psychiatric disorders. Further, in our discussions, it became clear that the emphasis on maintaining rigid boundaries between diagnoses was simply not reflecting the most up-to-date findings in genetics and family history research. For example, the research was showing that people who grew up in families with a high incidence of schizophrenia were likely to have kids with bipolar disorder, major depression, and neuro­developmental disorders. Findings like that underscore the fact that the old idea of a strict separation of disorders and of a separate genetic vulnerability hypothesis for each separate disorder was no longer tenable, given our current knowledge.

We now know that there are hundreds or thousands of genes that predispose someone to a condition like schizophrenia, and these genes interact with environmental exposures that will either turn on or turn off the gene in order to express a particular syndrome. This understanding requires us to take a different approach to the task of categorizing mental disorders. The idea that…