CAFFEINE REINFORCEMENT - THE ROLE OF WITHDRAWAL

This study examined caffeine's acute and withdrawal effects in moderat e caffeine consumers (mean = 379 mg/day caffeine) to compare the relat ive contributions each might have to caffeine reinforcement, Subjects were caffeine restricted on the night before each of three sessions, w hich generally occurred al weekly intervals; these restrictions lasted until the session was completed approximately 19 h later, During the first two sessions, subjects received either placebo or caffeine (each subject's average daily intake). These two conditions occurred using a double-blind, quasirandom, crossover design. Al the end of each sess ion subjects completed the POMS, a caffeine withdrawal questionnaire, and a Multiple-Choice Form on which subjects made a series of discrete choices between receiving the drug again or receiving varying amounts of money. This form also included negative money amounts to assess ho w much subjects would forfeit to avoid placebo (e.g., withdrawal sympt oms after placebo). During the third session, one of the previous choi ces was randomly selected and the consequence of that choice was imple mented. Placebo increased self-reported feelings of ''worn out,'' ''he adache'' and ''flu-like feelings,'' and decreased ''alert,'' ''upset s tomach,'' ''helpful,'' and ''well-being'' relative to caffeine. On the Multiple-Choice Forms, subjects chose to receive caffeine rather than an average of $0.38 and to forfeit $2.51 to avoid receiving placebo a gain. ''Headache'' was significantly correlated with amount of money f orfeited to avoid placebo, These: results suggest that, under these co nditions, choice of caffeine is more potently controlled by avoiding w ithdrawal than it is by the positive effects of caffeine.