Background: Previous studies showed that significant proportion of medical students consumed caffeine to face sleepdeprived daily schedules.
Objective: To monitor the trend of caffeinated-beverage consumption among Siriraj medical students as well as to study possible factors associated with caffeine dependency.
Material and Method: The questionnaire was distributed to a class of medical students for 2 consecutive years. Statistical analysis was performed for descriptive purpose.
Results: 269 (89.7%) and 225 (74.5%) questionnaires were returned in year 1 and year 2, respectively 16.2% refused to take caffeine-beverages totally. 13% of those who consumed caffeinated-beverages developed caffeine dependence. From logistical analysis, positive history of smoking-family member and female sex were the only other two factors associated with caffeine dependency (OR 2.19, 95% CI 1.04-4.61 and 1.76, 95% CI 1.01-3.07, respectively). Other investigated factors included: exercise (p = 0.08); sleep hours (p = 0.24); reading beverage labels (p = 0.87); alcohol consumption (p = 0.59); class performance (p = 0.87); family member coffee-drinking habits (p = 0.66); family member alcohol-drinking habits (p = 0.18); and family income (p = 0.06).
Conclusion: Caffeinated-beverage consumption was common among Siriraj medical students. No significant change was detected in the pattern of caffeinated-beverage consumption within the study period. Positive history of smoking family members and female sex were found as the only other two factors correlated with caffeine dependency.

Keywords: Caffeine dependence, Caffeine consumption, Medical student, Self-report, Caffeine labeling