Objectives: Dysfunctions in stress biology are hypothesized to contribute to anxiety disorders, and to be ameliorated during successful treatment, but limited clinical data exist to support this hypothesis. We evaluated whether increases in morning cortisol and the diurnal cortisol slope, markers of stress biology, are associated with clinical response to chamomile therapy among subjects with generalized anxiety disorder (GAD).
Methods: Among 45 subjects with DSM-IV diagnosed GAD in an open-label clinical trial of chamomile, salivary cortisol was assessed for three days each pre- and post-treatment, at 8am, 12pm, 4pm, and 8pm. Mixed model analyses assessed whether GAD symptom change predicted the degree to which cortisol levels changed during treatment.
Results: Symptom improvement during treatment was significantly associated with pre-to-post treatment changes in cortisol. Subjects who experienced more symptomatic improvement experienced significant increases in their morning salivary cortisol (β = 0.48, p < 0.001), and a greater decrease in cortisol from morning to the rest of the day (β = 0.55, p < 0.001). In addition, at baseline a lower cortisol level (β = −0.24, p = 0.023) and a lesser decrease in cortisol after morning (β = 0.30, p = 0.003) were associated with greater symptomatic improvement.
Conclusion: Increases in morning salivary cortisol and the diurnal cortisol slope are associated with symptom improvement in chamomile treatment of GAD. Response to treatment for GAD could partially stem from normalization of stress biology dysfunction, but further work involving establishing abnormalities within-sample, ruling out of confounds (e.g., sleep), and a placebo control is necessary to conclude an amelioration effect.