Caffeine has a reputation as an alertness drug that perks you up and helps you stay awake, but a 2010 British study shows that this might not be the case. You are not alone if you feel really tired after drinking caffeine instead of getting an energy boost or increased mental focus. Caffeine may have no effect on you, other than stopping withdrawal symptoms if you drink it regularly and have gone without it overnight.
Effects
Caffeine is supposed to stimulate your central nervous system, wake you up and make you energetic in moderate doses. Higher amounts make you nervous and irritable and trigger an upset stomach, headache and fast heartbeat, according to the KidsHealth.org website. Caffeine also has a reputation for causing insomnia, which means you have a hard time falling asleep after using it, but it is not uncommon for some people to be really tired after drinking caffeine despite its reputed effects.
Research
A 2010 study at Bristol University in the United Kingdom found that caffeine had no effect on research subjects who did not habitually consume it and only staved off withdrawal symptoms in people who use it regularly. The 379 subjects abstained from caffeine for 16 hours before the study. Some were then given a placebo, while others received caffeine. Later, they either got another placebo or a higher dose of the drug. Habitual caffeine users who got the placebo exhibited withdrawal symptoms, but none of the study participants had any energizing effect.
Considerations
Subjects in the Bristol University study who did not normally use caffeine or who only consumed moderate amounts developed mild anxiety when they received it in the study. This feeling might be mistaken by some people for caffeine-induced energy, according to researcher Peter Rogers. You may still feel really tired after consuming caffeine because the stimulation that comes with anxiety is not true wakefulness.
Contradictions
Other studies contradict the 2010 research that shows caffeine does not stimulate people. For example, a 2001 study at Cardiff University in the United Kingdom found that caffeine reduced fatigue and increased task performance in study participants. This effect was most prominent when the subjects' alertness was already impaired, so you are more likely to feel tired after drinking caffeine if you were not already fatigued beforehand. For example, it might not stimulate you during the day, but it might make you less tired working an overnight shift when you would normally be sleeping.
References
- Guardian.co.uk; Drinking Coffee Doesn't Make You More Alert, Caffeine Study Reveals; Jacob Aron ; June 2010
- Reuters; Caffeine Addicts Get No Real Perk from Morning Cup; Kate Kelland; June 2010
- KidsHealth.org; Caffeine Confusion; September 2010
- Human Psychopharmacology; The Effects of Caffeine on Simulated Driving, Subjective Alertness and Sustained Attention; C. Brice & A. Smith; October 2001
- Neuropsychopharmacology; Association of the Anxiogenic and Alerting Effects of Caffeine with ADORA2A and ADORA1 Polymorphisms and Habitual Level of Caffeine Consumption; Peter Rogers et. al.; June 2010
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