Am J Psychiatry 1997; 154:371-377
Copyright © 1997 by American Psychiatric Association
Revisiting the factor structure for positive and negative symptoms: evidence from a large heterogeneous group of psychiatric patients
R Toomey, WS Kremen, JC Simpson, JA Samson, LJ Seidman, MJ Lyons, SV Faraone and MT Tsuang
Harvard Medical School Department of Psychiatry, Massachusetts Mental Health Center, Boston 02115, USA.
OBJECTIVE: The factor structures of individual positive and negative
symptoms as well as global ratings were examined in a diagnostically
heterogeneous group of subjects. METHOD: Subjects were identified through a
clinical and family study of patients with major psychoses at a VA medical
center and evaluated with the Scale for the Assessment of Negative Symptoms
and the Scale for the Assessment of Positive Symptoms. For the examination
of global-level factor structures (N = 630), both principal-component
analysis and factor analysis with orthogonal rotation were used. Factor
analysis was used for the examination of item-level factor structures as
well (N = 549). RESULTS: The principal-component analysis of global ratings
revealed three factors: negative symptoms, positive symptoms, and
disorganization. The factor analysis of global ratings revealed a negative
symptom factor and a positive symptom factor. The item-level factor
analysis revealed two negative symptom factors (diminished expression and
disordered relating), two positive symptom factors (bizarre delusions and
auditory hallucinations), and a disorganization factor. CONCLUSIONS: The
generation of additional meaningful factors at the item level suggests that
important information about symptoms is lost when only global ratings are
viewed. Future work should explore clinical and pathological correlates of
the more differentiated item-level symptom dimensions.
