Caffeine Enhances the Physiological Response to Occupational Stress in Medical Students

Caffeine (3.3 mg/kg) was tested against a placebo in 20 male medical students during periods of low (no exams) versus high (final exams) work stress. On each of 8 test days, heart rate and blood pressure were measured at baseline and over a 40-min postdrug interval; immediately afterward, blood was drawn to test plasma cortisol and serum lipid concentrations. Exams increased heart rate (p < .005) and systolic blood pressure (p < .02). Caffeine decreased heart rate (p < .0001) and increased systolic blood pressure (p < .005), diastolic blood pressure (p < .0001), plasma cortisol levels (p < .01), and serum cholesterol levels (p < .02). Caffeine effects were additive with those of exams, and together they increased the number of men showing systolic blood pressures in the borderline hypertensive range. Thus, caffeine use during periods of increased occupational stress may enhance the cumulative stress response.