So, beyond pharmacological clock modulation, drugs that alter consciousness broadly often secondarily alter time perception by changing what the mind is attending to or capable of processing .

Looking at quantitative vs. qualitative effects: stimulants and simple sedatives primarily cause quantitative changes in timing (people err in one direction on interval tasks, but they generally still understand that time is flowing). Psychedelics, cannabis, and dissociatives often add a qualitative layer – users report that their entire... See more

This illustrates the earlier point about attention: if a stimulant greatly enhances focus on a particular activity to the exclusion of clock-watching, the person might underestimate time (time seems to fly) despite the physiological tendency of the drug to speed the clock

Intriguingly, this effect was not dose-dependent within the range tested: even a low psychoactive dose produced nearly the same time dilation as a higher dose