Rejection sensitivity and pain in bipolar versus unipolar depression

Objectives: Recent neuroimaging studies support the contention that depression, pain distress, and rejection distress share the same neurobiological circuits. In two recently published studies we confirmed the hypothesis that the perception of increased pain during both treatment-refractory depression (predominantly unipolar) and difficult-to-treat bipolar depression was related to increased state rejection sensitivity (i.e., rejection sensitivity when depressed). In the present study, we aimed to compare the correlates of pain and rejection sensitivity in individuals with bipolar versus unipolar depression and test the hypothesis that bipolar disorder may be distinguished from unipolar depression both by an increased perception of pain and heightened rejection sensitivity during depression. Methods: We analyzed data from 113 bipolar and 146 unipolar depressed patients presenting to the Black Dog Institute, Sydney, Australia. The patients all met DSM-IV criteria for bipolar disorder or unipolar depression (major depressive disorder). Results: Bipolar disorder predicted a major increase in state rejection sensitivity when depressed (p = 0.001), whereas trait rejection sensitivity (i.e., a long-standing pattern of rejection sensitivity) was not predicted by polarity. A major increase in the experience of headaches (p = 0.007), chest pain (p < 0.001), and body aches and pains (p = 0.02) during depression was predicted by a major increase in state rejection sensitivity for both bipolar and unipolar depression. Conclusions: State, but not trait, rejection sensitivity is significantly predicted by bipolar depression, suggesting that this might be considered as a state marker for bipolar depression and taken into account in the clinical differentiation of bipolar and unipolar depression.