Recent quotes:

Why Are There No Biological Tests in Psychiatry? - Scientific American Blog Network

we must also not minimize the grave practical problems and limitations associated with not having biological tests to identify psychiatric disorders. Most troubling is the fact that the overwhelming majority of prescriptions for psychotropic medicines are written by primary care physicians who often have little training in psychiatry; little time to perform an adequate diagnostic evaluation; a tendency to depend on tests rather than talking to patients; and too great a susceptibility to quick trigger diagnosis and poorly chosen pill solutions (fostered by aggressive and misleading drug company marketing). The lack of precise and easily available biological tests in psychiatry permits much loose diagnosing and cowboy prescribing.

DSM versus neuroscience

Compared with the psychiatric diagnoses listed in the Diagnostic and Statistical Manual of Mental Disorders (D.S.M.), which can be vague and flawed, brain-based research holds out the promise of a precise and truly scientific understanding of mental illness.