The largest mental health research organization in the world announced it will depart from the Diagnostic and Statistical Manual of Mental Disorders (DSM), the "Bible" of modern psychiatry, in favor of researching new diagnoses based on biomarkers, such as imaging and genetics.

As part of the federally-operated NIH, the National Institute of Mental Health (NIMH) supports mental health research throughout the U.S. through training grants, grants to research institutions, and its own internal research, with an operating budget of $1.5 billion dollars. The NIMH effectively dictates the future of how mental illness is conceptualized and treated in the U.S.

When describing the symptom-based diagnoses of the manual, now known in its fourth edition as the DSM-IV, Director of the National Institute of Mental Health, Dr. Thomas Insel wrote, "Patients with mental disorders deserve better."

Dr. Insel wrote in a statement that the NIMH will favor research that embeds mental health diagnoses in cognitive science, genetics, imaging, and other types of information. In 2011, the NIMH launched the Research Domain Criteria (RDoc), a framework for future research, which will hopefully produce a new set of diagnoses and diagnostic criteria.

Published by the American Psychiatric Association, the DSM is a guidebook for mental health professionals that lists mental disorders and outlines their standard diagnostic criteria. For example, under major depressive order, one would find the symptoms anhedonia, depressed mood, and reduced energy.

The strength of the DSM is in assuring that what a psychiatrist in New York describes as major depressive disorder is the same as a psychiatric nurse practitioner in Montana. However, its major weakness is that the creation of DSM diagnoses is unscientific, according to Dr. Insel. "[T]he DSM diagnoses are based on a consensus about clusters of clinical symptoms, not any objective laboratory measure."

Understanding psychiatric disorders in terms of physiology and laboratory values will make mental health research more similar to other fields in medicine. Just as heart disease can be measured in terms of a decrease in cardiac output, mental disorders like depression could be understood in terms of a yet-to-be-discovered biomarker in the blood or brain.

But even searching for physiologic evidence of existing disorders would rely too heavily on the existing DSM categories. These categories, much like each of their diagnostic symptoms, were created from expert consensus, rather than laboratory science.

Instead, the NIMH says it will favor research that examines symptoms across broad populations, such as all patients who go to a clinic, rather than rigidly-defined groups that correspond to the DSM criteria.

The fifth edition, known as the DSM-V, is scheduled for publication on May 22, 2013 and the proposed changes have been met with widely-publicized controversy.

The DSM-V will continue to be widely used, as the NIMH RDoC project is estimated to take about a decade of research.