Pain perception in patients with bipolar disorder and schizophrenia

Objective: Pain perception is reported to be altered in patients with depression and schizophrenia. However, few studies have investigated the pain perception in patients with bipolar disorders. We therefore aimed to compare pain sensitivity between patients with bipolar disorder, schizophrenia and controls. Methods: Study groups consisted of 30 patients with bipolar disorder, and control groups consisted of 27 patients with schizophrenia and 59 healthy subjects. Pain perception was assessed with cold pressor test (CPT) by exposure to ice-water. Results: Patients with schizophrenia had significantly higher pain thresholds (PTh) than patients with bipolar disorder. There were no differences between the PTh of patients with schizophrenia and healthy control subjects. However, patients with bipolar disorder had significantly lower pain tolerance (PT) in the CPT than patients with schizophrenia and corresponding healthy control subjects. Conclusions: The higher PTh in the schizophrenia group compared with the bipolar group found in this study supports further investigation of a potential difference in the pain perception between patients with schizophrenia and bipolar disorder. Theoretical implications of these findings and possible relevant behavioural and neurochemical mechanisms are discussed.