Stress, Anxiety, and Somatic Symptoms: A Comparison of Biomarkers in a Clinical Sample

Anxiety disorders are the most prevalent class of mental disorders, often characterized by a chronic course and comorbid psychopathology. The anxiety-stress literature utilizing cortisol as a biomarker of the hypothalamus pituitary adrenal (HPA) axis has been inconsistent. The establishment of salivary alpha-amylase (sAA) as a biomarker of sympathetic nervous system (SNS) activation allows researchers an opportunity to examine the stress response more fully. This study sought to explore relationships between trait anxiety and salivary stress biomarkers in an outpatient sample attending a specialized anxiety treatment center. Multiple regression and moderator analyses were conducted to examine associations between psychosocial and physiological variables. Forty-two adults participated. No zero-order association was detected between anxiety and stress in this sample, however, analyses suggest a moderating influence of chronicity on this relationship. Greater chronicity significantly strengthened the relationship between trait anxiety and sAA (ΔR2=0.166; P=0.038); while chronicity did not significantly moderate cortisol (ΔR2=0.082; P=0.187) a trend analysis suggests an attenuating effect of greater chronicity on the anxiety-cortisol relationship. A direct association was observed between the extent of psychiatric comorbidity and sAA (β = 0.433; P= 0.006), but not cortisol (β = 0.010; P= 0.955). This exploratory study supports the use of sAA in stress and anxiety research with diagnostically heterogeneous clinical samples. The results underscore the salience of anxiety chronicity and psychiatric comorbidity as factors which may influence the anxiety-stress relationship