• A study of 253 patients with primary and secondary affective disorders disclosed that psychotic features were more frequent among bipolar patients. Except for more frequent psychiatric hospitalization among unipolar patients with psychotic features, no demographic, family history, or parental home variable was found to distinguish between those with and without psychotic features. Chance variation probably accounted for the few symptoms whose frequencies were different depending on the presence or absence of psychotic features. The results failed to support the validity of a classification of affective disorders based on the presence or absence of psychotic features.
Guze SB, Woodruff RA, Clayton PJ. The Significance of Psychotic Affective Disorders. Arch Gen Psychiatry. 1975;32(9):1147–1150. doi:10.1001/archpsyc.1975.01760270079009