The association between caffeine consumption and an increase in alertness and performance has been well documented1-12. The European Food Safety Authority (EFSA) has concluded that a cause and effect relationship has been established between a 75mg serving of caffeine – the amount found in approximately one regular cup of coffee – and both increased attention (concentration) and alertness, mainly in situations of low arousal1.
The effects of caffeine on mental performance extend to other situations requiring alertness and concentration, such as safety and performance during night shifts, night time driving and coping with jet lag2,13-25. Caffeine consumption has been associated with a reduced risk of failures during night time working15 as well as a reduced risk of an accident occurring during long distance or monotonous driving18-25. Caffeine consumption may also help to address the problem of sleep inertia (a feeling of tiredness after an abrupt awakening) and this may explain in part the frequent choice of caffeinated beverages on wakening17.
Caffeine has also been associated with effects on mood and reaction time2,26-29. The repeated intake of 75mg of caffeine (the equivalent of one cup of coffee) every four hours has been linked with a pattern of sustained improvement of mood over the day, particularly in fatigued individuals26. However, high intakes may be associated with an increase in tense arousal including anxiety, nervousness and jitteriness (i.e. feeling shaky or uneasy)26. Some research has also suggested that the consumption of caffeinated beverages may help to relieve depressive symptoms or protect against depression30-34.
The effect of caffeine on increasing alertness can also cause sleep problems in some individuals, dependant on the amount of caffeine ingested over the whole day and the genetic makeup of individuals35-40. However, caffeine abstinence may help to improve sleep, in the context of sleep quality, and reduce the time taken to fall asleep41,42.
Brain mapping technology suggests that the physiological effects of caffeine do not lead to a cycle of dependence2,43,44. Whilst some individuals may experience symptoms of caffeine withdrawal on abrupt cessation of a regular caffeine intake, these symptoms are short-lived and can be avoided altogether if caffeine intake is decreased progressively2,45.
The content in this Topic Overview was last edited in July 2017. Papers in the Latest Research section and further resources are added regularly.