Chess on drugs discourse

There was actually a 2017 study examining the effects of Caffeine, Ritalin, and Provigil on club-level players. All three of the substances had the same pro and the same con. The pro is that all three increased the amount of time that players spent thinking about moves, and so theoretically made the players think deeper. The con was that, because of this, the experimental group tended to lose more games- they would just run out of time. With no clock involved, the Ritalin and Provigil (not the Caffeine interestingly) resulted in significant improvement, but with the clock involved, all three hurt more than they helped.

Source: "Methylphenidate, modafinil, and caffeine for cognitive enhancement in chess: A double-blind, randomised controlled trial"