Efficacy of Caffeine Versus Expectancy in Altering Caffeine-Related Symptoms

Abstract

The study investigated the independent and interactive effects of caffeine and expectancy on caffeine-related symptoms. High- and low-caffeine consumers were randomly assigned to either an expectancy or nonexpectancy instructional set and one of four caffeine doses. Subjects were administered the State-Trait Anxiety Inventory, (Spielberger & Gorsuch, 1970) and a Symptom Questionnaire (Christensen, White, Krietsch, & Steele, 1990) prior to and 45 min following consumption of one of the four caffeine doses. An analysis of covariance identified a significant main effect for the State-Trait Anxiety Inventory scores and significant main and interaction effects for four Symptom Questionnaire items. However, when the alpha levels were corrected for the increased probability of Type I error, using the Bonferroni procedure, these effects failed to achieve significance. These results suggest that previous reports of subjective caffeine effects are also suspect because of their failure to control for the increased probability of Type I error.

The Effects of Caffeine and Caffeine Withdrawal/Deprivation on Hostage Negotiator Performance

“…Although caffeine reduces calmness (Cole, Pope, LaBrie & Ionescu-Pioggia, 1978), its effect on subjective anxiety is unclear (Lee, Cameron & Greden, 1985;Uhde, Boulenger, Kimerson & Post, 1984). Also, the data on caffeine's effect on mood and aggression is unclear (Cherek, Steinberg & Brauch, 1983;Christensen, Miller & Johnson, 1991;File, Bond & Lister, 1982;Lieberman, Wurtman, Emde, Roberts & Coviella, 1987Svensson, Persson & Sjobert, 1980;Veleber & Templer, 1984). Some research has suggested caffeine usage makes people more aggressive, anxious, temperamental and emotional.…”