BACKGROUND: Major depressive disorder (MDD) is often complicated by anxiety symptoms, and anxiety disorders occur in approximately 30% of mood cases. This study examined the influence of anxiety comorbidity on the hypothalamic-pituitary-adrenal (HPA) axis response to stress in patients with MDD.
METHODS: Untreated subjects with pure MDD (n = 15), MDD with comorbid anxiety disorders (n = 18), and pure anxiety disorders (n = 15) were recruited by advertising. Age- and gender-matched control subjects were recruited for each subject with a psychiatric diagnosis (n = 48). All subjects underwent a social stressor, the Trier Social Stress Test (TSST), and blood was collected for adrenocorticotropic hormone (ACTH) and cortisol assay.
RESULTS: When all depressed patients (n = 33) were compared with their matched control subjects (n = 33), they showed a significantly greater ACTH response to the stressor; however, this exaggerated ACTH response was exclusively due to the depressed group with comorbid anxiety disorders. A similar but nonsignificant effect was observed in the cortisol response. Subjects with pure mood or pure anxiety disorders showed normal ACTH and cortisol responses to the TSST. All patient groups showed similar levels of TSST-induced anxiety.
CONCLUSIONS: Comorbid anxiety disorders might play a role in the increased activation of the HPA axis observed in patients with major depression.
