Reinforcing Effects of Caffeine in Coffee and Capsules

Abstract

In a residential research ward the reinforcing and subjective effects of caffeine were studied under double-blind conditions in volunteer subjects with histories of heavy coffee drinking. In Experiment 1, 6 subjects had 13 opportunities each day to self-administer either a caffeine (100 mg) or a placebo capsule for periods of 14 to 61 days. All subjects developed a clear preference for caffeine, with intake of caffeine becoming relatively stable after preference had been attained. Preference for caffeine was demonstrated whether or not preference testing was preceded by a period of 10 to 37 days of caffeine abstinence, suggesting that a recent history of heavy caffeine intake (tolerance/dependence) was not a necessary condition for caffeine to function as a reinforcer. In Experiment 2, 6 subjects had 10 opportunities each day to self-administer a cup of coffee or (on different days) a capsule, dependent upon completing a work requirement that progressively increased and then decreased over days. Each day, one of four conditions was studied: caffeinated coffee (100 mg/cup), decaffeinated coffee, caffeine capsules (100 mg/capsule), or placebo capsules. Caffeinated coffee maintained the most self-administration, significantly higher than decaffeinated coffee and placebo capsules but not different from caffeine capsules. Both decaffeinated coffee and caffeine capsules were significantly higher than placebo capsules but not different from each other. In both experiments, subject ratings of "liking" of coffee or capsules covaried with the self-administration measures. These experiments provide the clearest demonstrations to date of the reinforcing effects of caffeine in capsules and in coffee.

Acute d-amphetamine pretreatment does not alter stimulant self-administration in humans

“…The current findings support those of previous studies that have used the modified progressiveratio procedure and demonstrated that it is sensitive to the reinforcing effects of a number of drugs including heroin, caffeine, marijuana, pentobarbital, d-amphetamine, and methylphenidate Griffiths et al, 1989;Haney et al, 1997;McLeod and Griffiths, 1983;Rush et al, 2001;Stoops et al, 2004). Results from those studies have also demonstrated that the progressive-ratio procedure is sensitive to manipulation of both pharmacological (e.g., dose or pretreatment agent) (e.g., Comer et al, 1997; and environmental variables (e.g., alternative reinforcers or behavioral requirements following drug administration) (e.g., Stoops et al, 2005a;2005b).…”

Effects of price, ‘openness’ of the economy and magnitude of the alternative reinforcer on responding for caffeinated coffee

“…This pattern, observed for the group, was also apparent for most individual subjects. Using a somewhat different protocol in which price changes occurred over sessions, similar effects of price on caffeinated coffee self-administration have been reported by Griffiths et al (1989). Further, experiments examining reinforcers other than coffee have noted similar effects of price increases on responding and the amount of a commodity obtained (e.g.…”

The effects of caffeine on ambulatory blood pressure, heart rate, and mood in coffee drinkers

“…The nonsignificant effect of caffeine on Positive Affectivity and tiredness was surprising, as the literature is generally consistent in reporting decreases in fatigue (Silverman and Griffiths, 1992;Griffiths et al, 1989). It is unclear why caffeine did not alter self-reported Positive Affectivity or tiredness.…”