Lifehacker says:

A 1995 study suggests that humans become tolerant to their daily dose of caffeine—whether a single soda or a serious espresso habit—somewhere between a week and 12 days.

They don't link the actual study or give any more detail on it. I suspect it might be pretty useless since the dose was apparently left to the user. But maybe the rest of world has missed this one important study...

In contrast, a recent review says:

Although complete tolerance does not occur at low doses, tolerance to some of the effects of caffeine can occur after chronic administration of very high doses of the drug (i.e., 750–1200 mg/day).

cited from

Juliano LM. Ferré S. Griffiths RR. Saitz R. The pharmacology of caffeine. In: Ries R.K., editor; Fiellin D.A., editor; Miller S.C., editor; Principles of Addiction Medicine. Fourth. Philadelphia, PA: Lippincott Williams & Wilkins; 2009. pp. 159–178.

I checked the latter book, which has something like 2 paragraphs on the topic, with about 8 citations, but none of the papers cited there is from 1995, nor does the book support the idea that any dose will cause tolerance (in fact it says almost exactly the same thing as the paragraph quoted above.)

So, my question is: can anyone locate the 1995 study Lifehacker mentions?

  • $\begingroup$ Are you really looking for just that single study, or would others suffice? I think it's going to be relatively impossible to find as even if one finds a caffeine study in 1995 who knows if it's the correct study, or if the blog author even got the year right in the first place (it really really irritates me that even better respected journalistic outlets fail to bother any type of citation for the science they refer to - at least an author+date!). $\endgroup$ – Bryan Krause Aug 1 '18 at 17:25
  • $\begingroup$ @BryanKrause: well if the year is wrong or something trivial like that, I don't care. What I care about is that the claim is substantially similar because all studies cited in book used a high (and specific) caffeine dose, not "drink a soda or whatever caffeinated drink you usually do". So the claim that the latter regime causes tolerance seems to go beyond the usual claims one can find. By the way, I also checked en.wikipedia.org/wiki/Caffeine_dependence and no luck there either. $\endgroup$ – Fizz Aug 1 '18 at 17:47
  • 1
    $\begingroup$ See also this existing question on whether caffeine improves productivity in habituated users $\endgroup$ – Jeromy Anglim Aug 2 '18 at 2:32

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