Circulating levels of oxytocin may be elevated in complicated grief: a pilot study

Complicated grief (CG) is a debilitating syndrome characterized by persisting and intense distress and impairment after the death of a loved one. The biological mechanisms associated with this syndrome remain unclear but may involve neurobiological pathways implicated in the stress response and attachment systems. The neuropeptide oxytocin has been implicated in attachment and social behaviour, and loss of social bonds has been associated with disruptions in oxytocin signalling. Furthermore, prior research has reported associations between circulating oxytocin and other mental illnesses, including depression. The present pilot study aimed to examine plasma levels of oxytocin in bereaved adults with primary CG (n = 47) compared to age- and sex-matched bereaved individuals with primary Major Depressive Disorder (MDD) (n = 46), and bereaved individuals without any mental disorder (n = 46). In unadjusted analyses comparing groups according to primary diagnosis, oxytocin levels were significantly higher for primary CG compared to primary MDD (p = 0.013), but not compared to bereaved controls (p = 0.069). In adjusted regression models, having a primary or probable (Inventory of Complicated Grief ≥ 30) diagnosis of CG was associated with significantly higher oxytocin levels (p = 0.001). While additional research is needed, findings from our pilot study provide preliminary support for recent conceptualizations of CG implicating a role for oxytocin and the attachment system. Importantly, these findings contribute to the limited current knowledge about possible biological correlates of CG.