Negative symptoms as a risk factor for tardive dyskinesia in schizophrenia.

Investigation of the relationships between negative schizophrenic symptoms, abnormal involuntary movements and age in 179 chronic schizophrenic patients confirmed that both orofacial and trunk and limb dyskinesia are associated with negative symptoms, but only orofacial dyskinesia showed a significant increase in prevalence with increasing age. Estimation of the mean age of onset of orofacial dyskinesia from the observed variation in prevalence of orofacial dyskinesia with age indicated that patients having negative symptoms tend to develop orofacial dyskinesia at an earlier age. The estimated mean age of onset was 43.6 years in patients with substantial negative symptoms, and 54.6 years in patients without substantial negative symptoms. These findings support the proposal that the pathological process underlying negative symptoms can contribute to the occurrence of both orofacial and trunk and limb dyskinesia, but, in the case of orofacial dyskinesia, there is a synergistic interaction between the pathological process underlying negative symptoms and age-related neuronal changes.