It seems the higher doses of psilocybin are associated with the longest-lasting benefits.

I've always believed that people who smoked weed moderately seemed to be 'quicker' witted in older age(65-75). The positive effects can be negated by being fat/unhealthy/sedentary.

LSD, extacy types are more subjective. If you abuse them they fry your brain but in moderation they also seem to open new 'pathways' of thought.

Meth, crack, coke, no. They just cook your brain.