The neuroleptic hypothesis: study of the covariation of extrapyramidal and therapeutic drug effects.

A therapeutic trial with chlorpromazine was conducted with a homogeneous (for age and sex) group of recently admitted schizophrenic patients. Extrapyramidal effects were measured through quantitative analysis of digital tremor, after four days of fixed-dose treatment. Assessment of treatment efficacy was based on Brief Psychiatric Rating Scale ratings, done at the end of four weeks' treatment. Those patients whose tremor was least affected by drug were most likely to benefit from the treatment. Implications of this negative correlation for our understanding of the neuroleptic hypothesis and the closely associated dopamine hypothesis of schizophrenia are discussed.