Abnormal dexamethasone suppression test in daily chronic headache sufferers. 
The dexamethasone suppression test (DST) was administered in 48 daily chronic headache (DCH) sufferers, 37 of whom also suffered from mild to severe depression.  In 14 of 48 subjects (29.2%), cortisol values at 1600h were greater than 50 ng/ml, despite normal suppression at 0800h.  The escapers showed basal cortisol values and (Depression scale) scores on the Minnesota Multiphasic Personality Inventory higher than suppressors.  Thus, a group of DCH sufferers appeared to share a biochemical defect often seen in endogenous depression.  The escape from dexamethasone suppression could be a psychobiological indicator of vulnerability to develop depressive disorder and/or chronic pain complaints.