Personal and family history of suicidal behaviour is associated with lower peripheral cortisol in depressed outpatients.

BACKGROUND: Suicidal behaviour aggregates in families and HPA-axis dysregulation may help explain part of this familial aggregation. Nevertheless, exogenous manipulation of the HPA-axis has yielded mixed results. Naturalistic and non-pharmacological inductions of the HPA-axis do not suggest hyper-responsiveness, yet suggest greater cognitive consequences of stress in individuals at risk for suicide. In this study, we aimed to characterize the relationship between plasma cortisol and an increased risk for suicide, as defined by family history.
METHOD: Patients (N=148) with depressive disorders underwent psychopathological assessment, including structured investigation of past suicidal behaviour and underwent laboratory blood testing of cortisol. They also completed a family history interview investigating family psychopathology and suicidal behaviour, representing data on 848 first degree relatives. The relationship between plasma cortisol, past suicidal behaviour and suicidal behaviour among first degree relatives was examined.
RESULTS: Lower levels of plasma cortisol were associated with a personal and family history of suicidal behaviour, as well as a family history of depression among first degree relatives. Multivariate analyses controlling for significant psychopathology replicated the association between lower levels of plasma cortisol, a family history of suicidal behaviour and personal history of suicide attempts, but not a family history of depression. Controlling for personal history of suicide attempts revealed an independent association between plasma cortisol and family history of suicidal behaviour, with an additional contribution by family history of depression in predicting the latter.
CONCLUSIONS: Lower plasma cortisol is associated with a family history of suicide among depressed outpatients, independent of psychopathology and previous suicide attempts.