Abstract

EFFECTS OF CAFFEINE AND CAFFEINE WITHDRAWAL ON SUSTAINED ATTENTION, ENCODING OF NEW INFORMATION AND SEMANTIC MEMORY

Andrew P. Smith*, PhD

Abstract

Background: The behavioural effects of caffeine are well established, but there has been a debate about the underlying mechanisms. It has been suggested that caffeine withdrawal may impair cognitive performance and that the beneficial effects of caffeine might represent the removal of the deleterious effects of caffeine deprivation rather than an actual net benefit due to caffeine use. This view was tested here using a washout methodology. Method: The study had three parts. The first examined the effects of two doses of caffeine (1.5 mg/Kg and 3mg/Kg) and placebo on sustained attention, encoding new information and retrieval from semantic memory. The participants were 144 university students. Following this, half of the participants were given caffeinated coffee and tea to drink for a week, whereas the others were given decaffeinated products. Performance was tested each day. At the end of the week, the acute caffeine challenge was repeated. Results: The results showed that in part one of the study, administration of caffeine improved performance. In contrast, there was no evidence of impairment when participants were deprived of caffeine. It has been argued that participants should be deprived of caffeine for about a week to remove the adverse effects of deprivation before studies of the acute effects of caffeine are carried out. This was done here, and the beneficial effects of caffeine were still observed after a week of caffeine deprivation. Conclusions: These results support the view that caffeine consumption benefits performance, whereas caffeine withdrawal produces no impairments. Indeed, the effects of acute caffeine ingestion did not reflect the reversal of the effects of caffeine withdrawal.

Keywords: Caffeine; Caffeine withdrawal; Sustained attention; Semantic memory; Encoding of new information.