Nociceptive Reflex in Patients With Schizophrenia: A Case-Control Study

Background: Diminished pain sensitivity has been reported in patients in the acute phase of psychosis, as well as in stable patients. The cause of hypoalgesia in those patients is unknown. The aim of this study was to investigate the sensory thresholds, pain modalities, or other factors contributing to the perception or expression of physical pain in patients with schizophrenia (SCZ). Methods: This case-control study was conducted on 24 patients with SCZ and 12 healthy controls. Patients with SCZ were assessed by the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Positive and Negative Symptom Scale and Schizophrenia Cognition Rating Scale. All participants were subjected to full medical and neurological examination and nociceptive reflex. Results: There was no significant difference between cases and controls in nociceptive threshold, while it showed a significant difference at the subjective pain threshold as the case group needed a higher intensity of current to perceive as painful. There was a significant positive correlation between age, duration of SCZ and number of episodes and the nociceptive reflex. Also, there was a significant positive correlation between the negative symptoms of SCZ and cognitive impairment on one arm and the subjective pain threshold on the other arm. Conclusion: The pain insensitivity in patients with SCZ is not related to physiological changes in the nociceptive pathway, but rather may be related to change in the experience and expression of pain. Older age, longer duration of disease, more frequent episodes, negative symptoms, and cognitive impairment, but not antipsychotic medications, all are positively correlated with the increase in subjective pain threshold. J Neurol Res. 2021;11(1-2):20-26 doi: https://doi.org/10.14740/jnr656