A complex relationship exists between mood and pain, which is supported by different pain tolerance in clinically depressed patients compared to healthy people. In the present study we aimed to investigate pressure pain threshold (PPT) in unipolar and bipolar depressed patients and assess any differences between these two diagnoses.
This study included 40 patients diagnosed with unipolar depression and 89 patients diagnosed with bipolar depression according to DSM-IV criteria, also 40 healthy, age and gender-matched subjects without any known disease that could affect pain threshold were included in the study as a control group. PPT for mechanical pressure was examined by a handheld algometer at three body points. Student's t-test and analysis of variance was used to assess statistical differences between groups. The predictive level was investigated by univariate and multivariable linear regressions.
Depressed patients had significantly higher PPT than that in controls, and bipolar depressed patients had significantly higher PPT than that in unipolar depressed patients. PPT was also significantly associated with gender and use of anticonvulsant drugs.
Bipolar patient group was observed to have higher pain thresholds than unipolar depression and control group in this study. Therefore, better understanding of the pain risk and burden of this group is an important step in improving the clinical outcomes of these patients.