Caffeine consumption questionnaire: a standardized measure for caffeine consumption in undergraduate students.

Undergraduate students (N=691) were given the 1992 Caffeine Consumption Questionnaire of Landrum and provided information on age, sex, and year in school. A subset (n = 168) of those completing the questionnaire were also given the Morningness-Eveningness Questionnaire of Horne and Ostberg. Analysis indicated that the average intake of caffeine was roughly 1,600 mg, i.e., a range from 13 mg to 21,840 mg per week. Older students consumed more caffeine than younger ones, and students with an Evening personality preference consumed more caffeine in the evening and nighttime hours than those with a Morning personality preference. These results are discussed in the context of other caffeine studies. Caffeine consumption is an important issue, and a consistent measurement system should be used by various researchers testing different populations.