Caffeine consumption and anxiety and depressive symptomatology among medical students

Caffeine is one of the most widely consumed psychoactive substances in the world and is ingested in a variety of favorites, such as coffee, tea, cola and so on. Although it has been suggested that high dose caffeine users have more anxiety and depressive symptoms than low users, this relationship is not clear in Japan, where caffeine consumption is considered to be less than in Western countries. A questionnaire survey was conducted among medical students and 291 out of 423 initial subjects completed it. Among males, caffeine consumption was significantly and positively correlated with anxiety symptoms, when alcohol use and smoking habit were adjusted. However, there was no relationship between caffeine consumption and depressive symptoms. Among females, although there was no association between caffeine consumption and anxiety symptoms, high dose caffeine users showed less depressive symptoms than moderate and low users, when alcohol use was adjusted. It is suggested that caffeine use is one of the important factors, in researching psychological health among the general population. We need further epidemiological studies to determine whether there is a causal relationship between caffeine and psychological ill health or not.