Effects of caffeine on mood and performance: a study of realistic consumption

  • Published: Psychopharmacology 164:188–192 DOI 10.1007/s00213-002-1175-2 (2002)
  • Authors: Brice, C.F. & Smith, A.P.
  • Date Added: 29 Dec 2013
  • Last Update: 29 Dec 2013
  • Format: pdf


The present study aimed to determine whether a realistic drinking regime (multiple small doses – 4[1]65 mg over a 5-hour period) produced the same effects as a single large dose (200 mg).


A double-blind, placebo controlled, within-subjects experiment was, therefore, carried out. The participants (n=24) attended for four sessions. Each session started with a baseline measurement of mood and performance at 0930 hours. On two of the sessions, coffee was then consumed at 1000, 1100, 1200 and 1300 hours. In one of these sessions 65 mg caffeine was added to the de-caffeinated coffee. In the other two sessions, the participants consumed coffee at 1300 hours and 200 mg caffeine was added in one of the sessions. The volunteers completed the battery of tests again at 1500 hours.

Key Findings:

  • The results showed that in both consumption regimes, caffeine led to increased alertness and anxiety and improved performance on simple and choice reactive tasks, a cognitive vigilance task, a task requiring sustained response and a dual task involving tracking and target detection.


Caffeine, mood, reaction time, sustained attention, dual tasks, performance


This research further reinforces the positive impact of caffeine consumption to assist in counteracting the effects of driver fatigue. Again, there must be some caution allocated to the use of caffeine as there are also some negative effects. Caffeine has been shown (Smith, 2002) to increase anxiety and impair sleep. There is also some evidence that fine motor control may be impaired as a function of the increase in anxiety.