The positive/negative symptom distinction in psychoses. A replication and extension of previous findings.

The independence and internal consistency of Andreasen's positive and negative symptom scales was found to be good for schizophrenics but not for a comparison group of manic patients, supporting the assumption that the symptom distinction is diagnosis specific. Discriminant function analysis revealed that ratings of positive and negative symptoms are capable of predicting diagnostic category for the two groups with a high degree of accuracy.