Debilitating anxiety affects 6.8 million Americans. Cortisol is an established measure of the stress response which reflects the hypothalamic-pituitary-adrenal (HPA) axis activity. However, salivary alpha-amylase (sAA) is a relatively new measure of the stress response, and it reflects the sympathetic-adrenal-medullary pathway (SAM pathway) activity. Our aim was to compare these two aspects of the stress response in a Generalized Anxiety Disorder (GAD) and a non-clinical population under a stressful stimulus (Knee replacement surgery video). To our knowledge this is the first time anyone has looked at both sAA and cortisol together with respect to GAD. We hypothesized that both cortisol and sAA levels would raise from pre-stimulus to post-stimulus, but not in concert. Forty-six college students were assessed for GADs and randomly assigned to watch a stressful or neutral video. Saliva samples were taken at the beginning of the study, immediately after the video, and 30 minutes after the video. Participants were also given the Taylor Manifest Anxiety Scale TMAS and Beck Anxiety Inventory BAI as measures of state and trait anxiety. There was a significant difference between GAD and non-clinical groups for the TMAS and a significant group by condition interaction for baseline cortisol. Our GAD, stress sub-group had a significantly raised baseline cortisol level. Although the GAD and Non-clinical groups did not differ significantly with regard to baseline cortisol levels, it was in the hypothesized direction. Moreover, baseline cortisol levels were inversely related to baseline sAA levels. The findings suggest that cortisol and sAA show contrary diurnal responses
