Loss of efferent vagal activity in acute schizophrenia

An increased heart rate has been reported in schizophrenia. It is unclear whether this is due to disease-related autonomic nervous system changes or a side effect of antipsychotic medication. Altered cardiac autonomic function might to some extent account for the elevated cardiovascular mortality rate of schizophrenic patients. We assessed heart rate variability (HRV) in 30 acute unmedicated schizophrenic patients and matched controls. Patients were re-investigated 2--4 days after initiation of treatment to assess effects of medication. Our study demonstrates that non-medicated schizophrenic patients were significantly different in heart rate (increase) and parasympathetic parameters (loss of efferent vagal activity) at rest and during deep respiration. No significant effect was found after initiation of neuroleptic therapy. We found a correlation between duration of disease and parasympathetic parameters as well as very low frequency power (VLF) and delusion (SAPS subscale). These data suggest that schizophrenia is accompanied by a loss of vagal efferent activity, probably due to disturbed cortical-subcortical circuits modulating the autonomic nervous system in acute psychosis. The definite mechanisms by which vagal activity might be suppressed in schizophrenia are unknown. Parasympathetic hypoactivity might increase the risk for sudden cardiac death and arrhythmias in this disease. Future studies are warranted to investigate the interaction between cardiac autonomic function and schizophrenia and to identify patients on risk.