BACKGROUND: Panic disorder (PD) has been associated with the altered circadian rhythm of the hypothalamic-pituitary-adrenocortical (HPA) axis. The findings regarding the stress-specific functioning of the HPA-system are inconsistent. It is also unclear whether the HPA-system response after the Corticotropin-Releasing-Hormone (CRH) challenge becomes altered.

METHODS: For this study, the dexamethasone-corticotropin-releasing-hormone (DEX-CRH) test was implemented to assess the HPA-axis reactivity indicated by the plasma adreno-corticotropin-hormone (ACTH) and the cortisol release. The sample included 32 patients diagnosed with PD in a Structured Clinical Interview (SCID). Fourteen male and eighteen female patients, [mean age = 33.50 years, SD = 12.76] were matched with 32 healthy controls by age and gender. Moreover, a sample of patients with unipolar depression (n = 21, ten females) was examined as a clinical control group.

RESULTS: In healthy controls as well as in patients with PD and patients with unipolar depression, the ACTH and the cortisol response increased significantly due to the CRH injection after dexamethasone pre-treatment. There were differences between the healthy controls and the patients with PD in the plasma cortisol response pattern, however, not in the ACTH. The patients with PD showed a decreased CRH-induced plasma cortisol response. A median-split gave evidence that patients suffering from PD longer than two years showed a remarkably higher HPA-axis reactivity under CRH-injection than patients suffering from PD two years or less.

CONCLUSION: These findings provide strong evidence that patients with PD show some dissociation between ACTH and cortisol response under the DEX-CRH test with strong indicators that the length of the duration of the psychopathology is a risk factor for an increased reactivity of the HPA-axis in patients with PD.