Effect of anticholinergics on positive and negative symptoms in schizophrenia.

Anticholinergic drugs have been assumed to have no effects on schizophrenic symptomatology. Some studies suggest, however, that anticholinergic agents may antagonize the beneficial effect of neuroleptics on positive symptoms and partially ameliorate negative symptoms. Virtually all studies have been conducted in patients receiving concomitant neuroleptic treatment, raising the possibility that neuroleptics may obscure or modify any "true" anticholinergic effect on schizophrenic symptoms. To evaluate the hypothesis that anticholinergics may increase positive and decrease negative schizophrenic symptoms, we assessed the effect of biperiden on symptoms in the medication-free state. We studied the effect of biperiden 8 mg/day for 2 days on positive and negative symptoms in 40 otherwise drug-free schizophrenic inpatients. Biperiden produced a significant increase in positive symptoms (t = 6.7, p < .001) and reduction in negative symptoms (t = -3.4, p < .01). These data indicate that cholinergic modulation significantly affects positive and negative schizophrenic symptoms and suggest the need for systematic trials of cholinergic and anticholinergic agents in the treatment of positive and negative symptoms of schizophrenia, respectively.