Faster but not smarter: effects of caffeine and caffeine withdrawal on alertness and performance
- 9.6k Downloads
Despite 100 years of psychopharmacological research, the extent to which caffeine consumption benefits human functioning remains unclear.
To measure the effects of overnight caffeine abstinence and caffeine administration as a function of level of habitual caffeine consumption.
Medium-high (n = 212) and non-low (n = 157) caffeine consumers completed self-report measures and computer-based tasks before (starting at 10:30 AM) and after double-blind treatment with either caffeine (100 mg, then 150 mg) or placebo. The first treatment was given at 11:15 AM and the second at 12:45 PM, with post-treatment measures repeated twice between 1:45 PM and 3:30 PM.
Caffeine withdrawal was associated with some detrimental effects at 10:30 AM, and more severe effects, including greater sleepiness, lower mental alertness, and poorer performance on simple reaction time, choice reaction time and recognition memory tasks, later in the afternoon. Caffeine improved these measures in medium-high consumers but, apart from decreasing sleepiness, had little effect on them in non-low consumers. The failure of caffeine to increase mental alertness and improve mental performance in non-low consumers was related to a substantial caffeine-induced increase in anxiety/jitteriness that offset the benefit of decreased sleepiness. Caffeine enhanced physical performance (faster tapping speed and faster simple and choice reaction times) in both medium-high and non-low consumers.
While caffeine benefits motor performance and tolerance develops to its tendency to increase anxiety/jitteriness, tolerance to its effects on sleepiness means that frequent consumption fails to enhance mental alertness and mental performance.
KeywordsCaffeine Tolerance Withdrawal Mental performance Physical performance Reaction time Cognition Alertness Sleep Anxiety
This research was funded by a grant (BBS/B/01855) from the UK Biotechnology and Biological Sciences Research Council. We thank the volunteers who participated in this study and our colleagues Professor Richard Evershed and Dr. Pete Maxfield for their expertise in the analysis of salivary caffeine and paraxanthine concentrations. PJR has received grants to support research on caffeine from GlaxoSmithKline.
- Benjamin LT (2010) Coca-Cola—brain tonic or poison? The Psychologist 23:942–943Google Scholar
- Cohen J (1988) Statistical power analysis for the behavioral sciences, 2nd edn. Erlbaum, New JerseyGoogle Scholar
- Ferguson GA, Takane Y (1989) Statistical analysis in psychology and education, 3rd edn. McGraw Hill, New YorkGoogle Scholar
- Heatherley SV, Mullings EL, Tidbury MA, Rogers PJ (2006) Caffeine consumption among a sample of UK adults. Appetite 47:266Google Scholar
- Rogers PJ (2000) Caf or decaf?—impact of regular caffeine consumption on alertness, and mental and physical performance. In: McNulty GJ (ed) Proceedings of the 3rd International Conference on Quality, Reliability, and Maintenance. Professional Engineering, Bury St. Edmonds, Sulfolk, pp 343–346Google Scholar
- Rogers PJ, O’Dell RJ, Richardson NJ (1995a) Coffee and tea drinking: early experience and perceived benefits. Appetite 24:197Google Scholar
- Rogers PJ, Hohoff C, Heatherley SV, Mullings EL, Maxfield PJ, Evershed RP, Deckert J, Nutt DJ (2010) Association of the anxiogenic and alerting effects of caffeine with ADORA2A and ADORA1 polymorphisms and habitual level of caffeine consumption. Neuropsychopharmacology 35:1973–1983PubMedCrossRefGoogle Scholar
- Sigmon SC, Herning RI, Better W, Cadet JL, Griffiths RJ (2009) Caffeine withdrawal, acute effects, tolerance, and absence of net beneficial effects of chronic administration: cerebral blood flow velocity, quantitative EEG, and subjective effects. Psychopharmacology 204:573–585PubMedCrossRefGoogle Scholar
- Smit HJ, Rogers PJ (2007) Effects of caffeine on mood. In: Smith BD, Gupta U, Gupta BS (eds) Caffeine and activation theory: effects on health and behavior. CRC, Boca Raton, pp 229–282Google Scholar
- Smith JE (2011) Caffeine, theanine and anxiety; fMRI and behavioural studies. Ph.D. thesis, University of Bristol, BristolGoogle Scholar
- Tabachnick BG, Fidell LS (2007) Using multivariate statistics, 5th edn. Pearson, BostonGoogle Scholar