While in most healthy persons dexamethasone administration suppresses cortisol synthesis from the adrenal cortex, such suppression is not usually observed in patients with depression. We set out to investigate whether the dexamethasone suppression test (DST) reveals any neurobiological relationship between fibromyalgia (FM) and depression related to the hypothalamic-pituitary-adrenal (HPA) axis.
To discover a relationship between depression and FM we performed the DST in 20 FM patients with depression, 26 FM patients without depression and 20 healthy subjects serving as a control group.
Compared with the control group the cortisol level was found to be significantly higher in response to the DST in FM patients with depression (p = 0.03; z: -2.165), but not in those without depression (p = 0.153; z: -1.429). The cortisol level was not found to be statistically significant when patients with FM without depression were compared with the control group (p = 0.249; z: -1.152). In 7 FM patients with depression the DST failed to suppress cortisol; this was statistically significant compared with FM patients without depression (p = 0.014) and the control group(p = 0.008). Among FM patients without depression cortisol was not suppressed in one case. Cortisol was suppressed in all the controls. There was no statistically significant difference in cortisol suppression between FM patients without depression and the control group (p = 1.00).
Our findings show that the DST reveals no neurobiological relationship between FM and depression related to the HPA axis.