Cardiovascular responses to an acute psychological stressor are associated with the cortisol awakening response in individuals with chronic neck pain.
Shahidi B, Sannes T, Laudenslager M, Maluf KS. Cardiovascular responses to an acute psychological stressor are associated with the cortisol awakening response in individuals with chronic neck pain. Physiol Behav. 2015 Oct 15; 150:93-8.