Caffeine is the most widespread psychoactive drug in the world and is contained in large quantities in coffee and, in lower concentration, in other beverages that are regularly consumed to temporally ward of drowsiness or increase mental performance.
The main mechanism at work with caffeine to achieve the alleviation of drowsiness is by blocking adenosine receptors in the brain, due to a similar chemical structure as adenosine, that are a part of the sleep regulation mechanism.
While caffeine both does induce a number of scientifically validated positive and negative effects on humans for a short time after consumption, withdrawal symptoms are possible in the case of caffeine dependence and are recognized by the ICD-11 and DSM-5.
There are large genetically based differences in caffeine clearance time in the body, which might account for anecdotal accounts of varying sensitivity and prolonged effects of caffeine after ingestion.
|Percolated coffee||207 mL (7.0 US fl oz)||80–135||386–652|
|Drip coffee||207 mL (7.0 US fl oz)||115–175||555–845|
|Coffee, decaffeinated||207 mL (7.0 US fl oz)||5–15||24–72|
|Green tea||236 mL (8.0 US fl oz)||25||106|
|Black tea||236 mL (8.0 US fl oz)||42||178|
|Coca-Cola||355 mL (12.0 US fl oz)||34||96|
|Mountain Dew||355 mL (12.0 US fl oz)||54||154|
|Pepsi Zero Sugar||355 mL (12.0 US fl oz)||69||194|
|Red Bull||250 mL (8.5 US fl oz)||80||320|
Note: Caffeine content in tea can vary significantly based on leaf type and steeping time.
For the purpose of adapting to Polyphasic sleep, the community discourages the intake of caffeinated beverages due to the ability of caffeine to disrupt sleep, decrease the amount of SWS sleep in a sleep block and mask sleep deprivation symptoms during the adaptation period. The long half life of caffeine (particularly as contained in coffee), significantly outlasts both the perceptible cognitive boost and the inevitable following caffeine crash, proceeding to effect the next sleep block in a subtle but negative way.
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- Bjorness TE, Greene RW (September 2009). "Adenosine and Sleep". Current Neuropharmacology. 7 (3): 238–245. doi:10.2174/157015909789152182. PMC 2769007. PMID 20190965.
- "The structure of caffeine is very similar to adenosine, which allows it to bind to (all) the A1, A2a, A2b, and A3 ARs." in "Progress in Neuro-Psychopharmacology and Biological Psychiatry" by JuliusSchuster, Ellen S.Mitchell
- "CYP1A2 gene polymorphism has been shown to alter the expression or activity of the CYP1A2 enzyme (Rasmussen et al., 2002), which subsequently results in a large individual variability of caffeine clearance." in "Progress in Neuro-Psychopharmacology and Biological Psychiatry" by JuliusSchuster, Ellen S.Mitchell
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