- The base video I have talked about is from TedED. It's here [0].
- This study was done on rats in 1985 but verifies that caffeine tolerance is real [1].
- Another controlled study on humans about caffeine tolerance [2] involved one group taking caffeine and the others taking a placebo. Caffeine drinkers taking the placebo reported withdrawal symptoms, and non-drinkers taking caffeine reported overstimulation.
- A meta-study [3] details the symptoms and durations of caffeine withdrawal's effects. The paper cites that effects persist between 2 to 9 days, and the peak of the syndrome is around 20 to 51 hours. It also notes that caffeine introduction during this phase alleviates symptoms (This study basically confirms that what I have gone through after I stopped drinking coffee as I noted in a previous comment).
- This interesting study [4] explores the body's caffeine response via blood pressure change. Subjects are administered high doses of caffeine, and blood pressure is monitored. After day three, the blood pressure normalizes, and spikes disappear. The abstinence required to reset the pressure response is less than three weeks, pointing that the body resets caffeine tolerance in less than three weeks.
If you need the papers, or want more resources, please let me know.
Have a nice day.
[0]: https://www.youtube.com/watch?v=qOjvYRgjCyU
[1]: https://www.sciencedirect.com/science/article/pii/0024320585...
[2]: https://link.springer.com/article/10.1007/BF02245285
[3]: https://link.springer.com/article/10.1007/s00213-004-2000-x