Drug-induced parkinsonism: relationship to age at onset of schizophrenia.

On the basis of the association of negative schizophrenia with parkinsonism and early age of onset, we predicted that the latter two would covary, as reflecting a similar pathological process. To test this prediction, we studied in 40 neuroleptic-treated female schizophrenic patients with drug-induced movement disorders the association of age at onset with drug-induced parkinsonism and, for comparison, also with persistent tardive dyskinesia (TD) and acute drug-induced dystonia. We found that onset of schizophrenia during adolescence, significantly predicted the presence of parkinsonism but, by contrast, was unrelated to TD and acute drug-induced dystonia. Our findings suggest a specific association between early age at onset of schizophrenia and parkinsonism, implying that the former may be a risk factor for parkinsonism. The significance of these findings to the pathophysiology of negative schizophrenia and parkinsonism are discussed.