Background
: Although caffeine is commonly consumed substance and not seriously harmful as compared to alcohol and nicotine, Korea is planning to mark on the products which contain caffeine above a definite level with "containing large amounts caffeine". At this point in time, the study concerning caffeine related symptoms is in need.

Methods : After surveying university students by using self-administered questionnaires based on DSM-IV substance related disorder, healthy 810 subjects were assessed for socio-demographic characteristics and features of caffeine intake and its dependence, withdrawal, and intoxication.

Results : The mean amount of caffeine consumption in 810 subjects was 120.49 mg (median=93.0) per day. The major features of caffeine dependence were as follows: tolerance (61.1%), withdrawal (46.3%), using more or longer than intended (46.0%), and unsuccessful attempt to cut down or control use (12.6%). The prevalence was increased by daily caffeine consumption. Among 711 subjects who had experienced no caffeine consumption over 24 hours {amount of daily caffeine consumption was 116.0 mg (median=86.5)}, 6.19% showed significant distress in usual activity, and 22.1% used caffeine contents to avoid withdrawal symptoms. The prevalence of caffeine withdrawal based on DSM-IV research criteria was 2.67% and the frequency for symptoms were as follows: fatigue (37.7%), drowsiness (17.6%), headache (14.5%), an anxiety (8.3%). In addition, the prevalence of caffeine intoxication was 2.1% and the frequency for symptoms were as follows: insomnia (41.9%), diuresis (35.8%), tachycardia (26.7%), and gastrointestinal disturbance (23.3%).

Conclusion : The unwanted symptoms related to caffeine withdrawal or intoxication were common in students using caffeine. Therefore, major features of caffeine-related symptoms should be considered in primary care practice.