Caffeine expectancy questionnaire (CaffEQ) construction, psychometric properties and predictive validity

Beliefs about the effects of drugs, or drug outcome expectancies, are believed to play an important role in drug taking behavior. Caffeine is the most widely consumed behaviorally active drug in the world, yet little is known about the expectancies consumers have about its effects. The purpose of this investigation was to assess self-reported expectancies for caffeine among caffeine consumers and non-consumers in an attempt to develop a valid and reliable caffeine expectancy questionnaire (CaffEQ). The CaffEQ was administered to 1046 participants and a principal components analysis yielded a 7-factor solution accounting for 70% of the variance. Daily caffeine exposure was associated with greater positive expectancies and lower negative expectancies for caffeine, with the largest effect observed in the withdrawal avoidance scale. The scales of the CaffEQ also correlated with validated measures of sleep and anxiety. The CaffEQ is likely to be useful for both clinical and research purposes.