Caffeine effects on cardiovascular and neuroendocrine responses to acute psychosocial stress and their relationship to level of habitual caffeine consumption.
Level 2 - randomized trial
Placebo-controlled clinical trial testing acute physiological responses in healthy volunteers
PubMed 2195579 · doi:10.1097/00006842-199005000-00006
What was done
Researchers evaluated the physiological effects of acute caffeine administration (3.5 mg/kg) compared to placebo in 25 healthy male volunteers categorized as habitual or light caffeine consumers. Cardiovascular and neuroendocrine markers—specifically blood pressure, plasma norepinephrine, plasma epinephrine, and cortisol—were measured under resting conditions pre- and post-substance administration, during an acute laboratory psychosocial stress task, and during a post-stress recovery period.
What was found
Caffeine significantly increased resting blood pressure and resting plasma norepinephrine, which produced additive elevations when combined with the stress task. Furthermore, caffeine potentiated stress-induced surges in plasma epinephrine and cortisol, more than doubling the magnitude of these hormonal responses compared to the placebo condition. These effects occurred in both light and habitual caffeine users without significant differences in response magnitude based on habitual intake levels.
Why it matters
This study demonstrates that caffeine can amplify both cardiovascular and endocrine responses to acute mental stress without evident tolerance developing from regular caffeine consumption.
Limits
The sample size was small (n = 25) and restricted entirely to healthy males, limiting generalizability to females and broader populations. The abstract reports qualitative directions and proportional changes (e.g., more than doubling) but lacks exact numerical values, confidence intervals, and details on randomization methods or long-term clinical endpoints.
Cited by
- context In chronic caffeine users, caffeine consumption does not significantly increase cortisol levels.