Current diagnostic concepts in schizophrenia.

The diagnosis of psychiatric disorders currently relies primarily on clinical observation and evaluation of manifest psychopathology. Symptom-based diagnosis of schizophrenia defines a highly variable patient population and thus makes replication of research results difficult. However, this diagnostic approach is useful because it has established communicative value, encourages clinicians to rely on the diagnostic data most readily available (i.e., the patient's behavior), and relates directly to treatment plans. The author describes a 12-point symptom-based diagnostic system for schizophrenia that enhances the reliability and (presumably) validity of the diagnostic process. He then illustrates methods that can be used to select homogeneous schizophrenic populations for specialized research purposes.