Caffeine withdrawal and mood
Caffeine withdrawal has been widely studied because it is meant to provide crucial evidence on whether caf- feine is addictive or leads to some kind of dependence. The most frequent outcome measure has been reporting of headache, but mood has been examined in other studies. Ratcliff-Crain et al. (1989) reported that caffeine deprivation led to increased reporting of stress by heavy coffee drinkers. This has recently been confirmed by Schuh and Griffiths (1997), who found that caffeine withdrawal was associated with feelings of fatigue and decreased feelings of alertness. Indeed, Silverman et al. (1992) found that about 10% of volunteers with a moder- ate daily intake (235 mg per day) reported increased depression and anxiety when caffeine was withdrawn.
Other researchers (e.g. James, 1994) have argued that caffeine has no beneficial behavioral effects but merely removes negative effects associated with caffeine with- drawal. Smith (1995) has argued against this general view of caffeine effects on a number of grounds. First, it cannot account for the behavioral effects seen in animals or non- consumers, where withdrawal cannot occur. Secondly, caffeine withdrawal cannot account for behavioral changes following caffeine consumption after a short
period of abstinence or the greater effects of caffeine when arousal is low. Finally, claims about the negative effects of caffeine withdrawal require closer examination since they can often be interpreted in ways other than caf- feine dependence (e.g. expectancy—Smith, 1996a; Rubin and Smith, 1999). Indeed, in most of the studies that have demonstrated increases in negative effect following caffeine withdrawal, the subjects have not been blind but have been told or even instructed to abstain from caffeine. This is clearly very different from the double-blind methodology typically used to study effects of caffeine challenge.