Funnily enough, I just came across a study of ecstasy use in Mormon kids who didn’t take alcohol or other drugs... not sure if they were staying up all night raving but my prior is not. Apparently they didn’t suffer the same cognitive deficits found in other ecstasy users.
I wondered about this myself.
I think it is hard to pinpoint exactly since festival-goers often also consume a mix of different substances (the infamous "candy flipping") including alcohol instead of just straight mushrooms or LSD.