A PATH-ANALYTICAL APPROACH TO DIFFERENTIATE BETWEEN DIRECT AND INDIRECT DRUG EFFECTS ON NEGATIVE SYMPTOMS IN SCHIZOPHRENIC-PATIENTS - A REEVALUATION OF THE NORTH-AMERICAN RISPERIDONE STUDY

The hypothesis that differences in drug effects of risperidone and hal operidol on negative symptoms in schizophrenia an secondary to effects on positive, extrapyramidal, and depressive symptoms was investigated by means of an analysis of the data from the USA-Canada risperidone d ouble-blind randomized clinical trial of 523 chronic schizophrenic pat ients. Regression analyses in the total sample and within treatment gr oups confirmed a strong relationship between changes in negative sympt oms and the other variables studied (R(2) = 0.50-0.51, p < 0.001). Onl y depressive symptoms did not contribute significantly to these result s (p > 0.10). Path analysis showed that the greater mean change (p < 0 .05) of negative symptoms with risperidone compared to haloperidol cou ld not be fully explained by correlations with favourable effects on p ositive and extrapyramidal symptoms. The relationship between shift in extrapyramidal symptoms and shift in negative symptoms failed to reac h statistical significance; however, there was a clear tendency in the expected direction in both treatment groups.