_NIMH [developed] a new framework for defining mental illness. The result, unveiled in 2013, was the Research Domain Criteria (RDoC), a system created to flip the way researchers think about mental disorders. Unlike the DSM, RDoC isn’t organized by disorder; instead, it’s organized around specific symptoms, like fear, anhedonia (the inability to feel pleasure), and willingness or unwillingness to work. The system also lists the genes, neural circuits, physical response, and self-reported behavior associated with each symptom.
The theory behind this RDoC system is that treating a specific symptom will produce better results than treating a broad category of illness. Many depression patients exhibit anhedonia, for example, but many others don’t. But if researchers took a group of patients who all displayed anhedonia, regardless of their diagnosis (it’s also a common symptom of schizophrenia) and tested treatments for that very specific symptom, they would get better results for treating anhedonia_