The relationship of tardive dyskinesia to positive schizophrenia

Investigations aimed at identifying the clinical characteristics that discriminate Tardive dyskinesia (TD) from non-TD patients have yielded disparate findings. A number of studies have suggested that TD may be a feature of negative schizophrenia. In particular, the association of TD with high prevalence of "soft" neurological signs, cognitive deficits, and abnormal brain morphology on CT scan in some patients, have led several investigators to propose that negative schizophrenia may be a risk factor for TD. The neurochemical profile of TD, however, is not consistent with this hypothesis. In the following communication, we present our studies which suggest that TD is specific to and an intergral part of positive schizophrenia. The data suggest that schizophrenic patients with predominant positive symptoms may be at increased risk for the development of TD. In addition, we present evidence linking TD with left cerebral hemispheric dysfunction. By comparison, we provide evidence that negative schizophrenia is related to diencephalic damage, and discuss its relevance to negative schizophrenia and to Parkinsonism. We also provide evidence that negative schizophrenia may be a risk factor for acute drug-induced dystonia. Thus, these findings are consistent with our model that negative schizophrenia is a risk factor for Parkinsonism, whereas positive schizophrenia is related to TD. In analogy with the positive/negative dichotomy of schizophrenia, we propose that TD could be considered a "positive," where Parkinsonism a "negative" movement disorder.