The effects of psychoactive drugs and neuroleptics on language in normal subjects and schizophrenic patients: a review

A review of eighteen studies on psychoactive drugs and neuroleptics (NL) shows that in healthy subjects, alcohol, amphetamine, and secobarbital increase language production, d-amphetamine makes speech more complex, L-dopa focuses it, psilocybin makes it unfocused, and ketamine clearly impairs it. No studies examine neuroleptic effects on language in healthy people. In schizophrenic patients, conventional neuroleptics at therapeutic doses reduce language disorders clinically, linguistically, and psycholinguistically. When combined with other molecules, moderate chronic NL plus amphetamine improves verbal flow and reduces pauses and positive thought disorder, while NL plus fenfluramine impairs language measurements.

Study at a glance

Abstract

The aim of this survey is to present an overview of research into psychopharmacology as regards the effects of different psychoactive drugs and neuroleptics (NL) on language in normal subjects and schizophrenic patients. Eighteen studies that have investigated the effects of different drugs (alcohol, amphetamines, secobarbital, L-dopa, psilocybin, ketamine, fenfluramine) and neuroleptics (conventional and atypical) on language are reviewed. There are no studies concerning the effects of neuroleptics on language in healthy subjects. The results of the effects of other molecules indicate that language production can be increased (alcohol, amphetamine, secobarbital), rendered more complex (d-amphetamine), more focused (L-dopa) or more unfocused (psilocybin) and clearly impaired (ketamine). For schizophrenic patients, most studies show that conventional neuroleptic treatments, at a therapeutic dosage and in acute or chronic mode, reduce language disorders at all levels (clinic, linguistic, psycholinguistic). In conjunction with other molecules, the classical NL, when administered at a moderate dosage and in chronic mode, modify language in schizophrenia, either by improving the verbal flow and reducing pauses and positive thought disorder (NL + amphetamine) or by inducing an impairment in the language measurements (NL + fenfluramine). Clinical, methodological and theoretical considerations of results are debated in the framework of schizophrenic language disorders.