In traditional medical use, a categorical diagnosis conveys essential (although stereotypic) information about the signs and symptoms of a disease, its treatment, and its prognosis. Its utility derives from its generalizability. However, many of the shortcomings of categorical classification also reflect these same qualities. Diagnoses too often fail to capture important qualities of a disorder or do not sufficiently characterize a patient's particular symptoms. Recent editions of the Diagnostic and Statistical Manual of Mental Disorders (DSM), which have emphasized highly specific entry criteria to establish psychiatric conditions in a more homogeneous fashion, have sometimes resulted in enhanced reliability at the cost of diminished validity. The variability of psychiatric disorders often defies attempts to create strictly defined clusters amenable to syndrome classifications.