The effects of risperidone on the five dimensions of schizophrenia derived by factor analysis: combined results of the North American trials.
BACKGROUND
In two double-blind trials conducted in North America, 513 patients with chronic schizophrenia received risperidone, haloperidol, or placebo. In the present study, combined data from the two trials were analyzed.


METHODS
Patients were randomly assigned to receive placebo, fixed doses of risperidone (2, 6, 10, and 16 mg/day) or 20 mg/day of haloperidol for 8 weeks. Factor analysis of scores on the Positive and Negative Syndrome Scale (PANSS) produced five dimensions (negative symptoms, positive symptoms, disorganized thought, uncontrolled hostility/excitement, and anxiety/depression), similar to the five dimensions of previous factor-analytic studies of PANSS data.


RESULTS
Mean changes (symptom reductions) in PANSS factor scores from baseline to treatment Weeks 6 and 8 were significantly greater in patients receiving 6-16 mg/day of risperidone than in patients receiving placebo or haloperidol. The advantages of risperidone were greatest for negative symptoms, uncontrolled hostility/excitement, and anxiety/depression. Even at the lowest dose, 2 mg/day, risperidone was significantly (p < or = .05) superior to haloperidol in reducing negative symptoms. The differences in outcomes between risperidone and haloperidol on PANSS scores were not related to extrapyramidal symptoms.


CONCLUSIONS
Risperidone produced significantly (p < or = .05) greater improvements than haloperidol on all five dimensions. The large between-group differences on negative symptoms, hostility/excitement, and anxiety/depression suggest that risperidone and other serotonin/dopamine antagonists have qualitatively different effects from those of conventional antipsychotic agents.
Marder
S R
SR
Psychiatry Service, West Los Angeles VA Medical Center, Brentwood Division, CA 90037, USA.
Davis
J M
JM
Chouinard
G
G
D000293:Adolescent; D000328:Adult; D000368:Aged; D001480:Basal Ganglia Diseases / Q000139:chemically induced / Q000175:diagnosis; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005163:Factor Analysis, Statistical; D005260:Female; D006220:Haloperidol / Q000009:adverse effects / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D010919:Placebos; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data; D018967:Risperidone / Q000009:adverse effects / Q000627:therapeutic use*; D012559:Schizophrenia / Q000175:diagnosis / Q000188:drug therapy*; D012563:Schizophrenia, Paranoid / Q000175:diagnosis / Q000188:drug therapy / Q000523:psychology; D012565:Schizophrenic Psychology; D012720:Severity of Illness Index; D016896:Treatment Outcome
D010919:Placebos; D006220:Haloperidol; D018967:Risperidone