One major confounder is that caffeine is also a painkiller, many people have mild chronic pain, and I think there's a very plausible mechanism by which painkillers improve productivity, i.e. just allowing someone to focus better.
Anecdotally, I've noticed that "resetting" caffeine tolerance is very quick compared to most drugs, taking something like 2-3 days without caffeine for several people I know, including myself.
The studies I could find on caffeine are highly contradictory, e.g. from Wikipedia, "Caffeine has been shown to have positive, negative, and no effects on long-term memory."
I'm under the impression that there's no general evidence for stimulants increasing productivity, although there are several specific cases, such as e.g. treating ADHD.
Yes. When it comes to tolerance of stimulant drugs, there is such thing as a free lunch.
While you will get some tolerance, and ceasing use will give you some withdrawal effects, tolerance will eventually plateau unless you are taking far more than you should be. After tolerance is accounted for, using caffeine will still give you a higher baseline of productivity than taking nothing at all.
This question seems to conflate the claim that caffeine works as a stimulant, and the claim that in a meaningful sense stimulants increase productivity. I suspect this is true for measured productivity, but not at all obviously true for net production.
(Related: Talents, Blitzed: Drugs in the Third Reich)
I don't think this is the right question to ask. Even if the net alertness gain of a cup of coffee is 0, it is still worth consuming during those moments that alertness is worth more, and abstaining during those moments where relaxation is worth more. Net alertness is not net EV.
There are different ways to consume caffeine. A lot of people consume caffeine as part of their morning routine. It's useful to know whether or not that increases productivity even when there are also other ways to consume caffeine.
The answer there might also depend on how we're defining productivity.
I was reading some links earlier about longevity and biological processes/genetic processes (if that makes any sense...) that were linking neurological over-activity (which seems to be neurons being electrically active even when not really doing anything) to shorter lives and more rapid aging.
If caffeine serves to dampen down unnecessary activity that might lead to slower aging (ability to be more productive at a given age) and living longer so more total productivity.
re SatvikBeri's wiki observations, does that sound like a training rats to go 3 doors down type setting?
Caffeine stops surpression of neural activity. That's likely leading to more activity. At the same time there's some evidence that points at caffeine being positive for lifespan like https://www.aarp.org/health/healthy-living/info-2018/coffee-longevity-health-benefits.html and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3922918/ .
misread and though you were saying the caffeine was suppressing -- not that it was preventing the suppression!
I drink coffee once in about two to three months. It increases my productivity for about three hours, once it kicks in, and ruins my next day and a half (especially the night). It's probably different for people who keep a pool of caffeine in them, I think.
I drink 1-2 big cups of coffee a day. (Always one in the morning, sometimes another in the early afternoon, often the one in the early afternoon is half-caff.)
I find it consistently helpful – boosted focus & "it's fun to do stuff" energy for 3-4 hours, minimal crash, no trouble sleeping.
I think it's very much YMMV though... my partner is way more sensitive to caffeine than I am, and drinking coffee substantially increases her baseline anxiety.
Have you stopped drinking it sometime for two weeks and noticed that you had less energy afterwards?
I accidentally started withdrawing from caffeine a few months ago. It was pretty unpleasant – very low-energy & drowsy throughout the day plus a mild headache.
I drank coffee the next morning because I wanted to stop withdrawing.
I take the consistent boost of energy & focus after drinking coffee as pretty strong energy that it's working for me. (If it's just a placebo effect, it's a great placebo effect.)
Randomizing here would be difficult because of the withdrawal effects.
Caffeine raises human alertness by binding to adenosine receptors in the human brain. It prevents those receptors from binding adenosine and suppressing activity in the central nervous system.
Regular caffeine productions seems to result in the body building more adenosine receptors, but it's unclear to me whether or not the body produces enough adenosine receptors to fully cancel out the effect. Did anybody look deeper into the issue and knows the answer?