Carers of patients with psychiatric disorders show high levels of anxiety and depression, possibly mediated through disruption of the hypothalamo–pituitary–adrenal (HPA) axis. Among carers of patients with treatment-resistant depression (TRD), we set out to determine the psychological and physiological (HPA axis) consequences of caring, and the association of these consequences with long-term outcome in patients.
Thirty-five informal carers of patients with severe TRD requiring in-patient treatment were recruited and compared with 23 controls. HPA-axis activity was assessed by measuring post-awaking salivary cortisol. The Involvement Evaluation Questionnaire (IEQ) and the General Health Questionnaire-12 (GHQ-12) were administered to measure carer burden and psychiatric caseness respectively. Independent t tests were used to compare differences between carers and controls and a linear regression model was used to determine the association of post-awakening cortisol with carer status while controlling for confounding variables. Data on long-term patient outcome (12 to 83 months), measured using the Hamilton Depression Rating Scale (HAMD), were also obtained and linear regression was used to determine the association between cortisol output in carers and remission status in patients.
Carers experienced high carer burden and high psychiatric caseness. Carers showed reduced cortisol output after awakening, calculated as the area under the curve with respect to ground (AUCg), which remained significant after controlling for potential confounders. In a linear regression model, non-remission in patients was associated with reduced cortisol output in carers.
Caring for patients with TRD is associated with adverse psychological and physiological changes suggesting hypocortisolism post-awakening. These changes are associated with poor patient outcome.