ABSTRACT

Coffee is one of the most frequently consumed beverages worldwide and contains the bioactive constituent caffeine, which is the most commonly consumed psychostimulant. There have been mixed reports of coffee/caffeine's effects on mood disorders including anxiety and depression. The aim of this study was to evaluate correlations between coffee/caffeine consumption and salivary and plasma biomarkers associated with anxiety and depression in a healthy population. A cross-sectional study design was employed with participants completing a coffee and caffeine consumption questionnaire and providing either morning (n = 55) and/or afternoon (n = 54) saliva samples and/or a plasma sample (n = 39). Biological samples were examined for numerous biomarkers including amylase, prolactin, cortisol (all saliva), caffeine, TBX B2, PGE2, tryptophan and the kynurenine pathway catabolites (all plasma). Weak to moderate inverse or positive correlations between caffeinated coffee consumption and cortisol (R2 = -0.3220; P < 0.05; n = 55), kynurenine (R2 = 0.3878; P < 0.05; n = 39), and kynurenine-to-tryptophan ratio x 100 (R2 = 0.4092; P < 0.05; n = 39), respectively, were identified. Furthermore, positive correlations were identified between caffeine consumption and kynurenine (R2 = 0.3148; P < 0.05; n = 39), kynurenine-to-tryptophan ratio x 100 (R2 = 0.4023; P < 0.05; n = 39), and cortisol (R2 = - 0.2972; P < 0.05; n = 55); and plasma caffeine and kynurenine-to-tryptophan ratio x100 (R2 = 0.4297; P < 0.050; n = 39). The current study provides insights into changes associated with biomarkers induced by the consumption of caffeinated coffee and/or caffeine. Weak to moderate correlations were observed between caffeinated coffee consumption and cortisol, kynurenine, and kynurenine-to-tryptophan ratio. Additionally, weak to moderate correlations we also seen between caffeine and the plasma biomarkers, kynurenine and kynurenine-to-tryptophan ratio.

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