18 b/c then the human brain has grown enough so the person doesnt suffer immaturity...pot is known to stunt mental and matturity growth...and the mind genually stops growing at 18, 21 for sure....lol <3

of corse i first tried it at 15....and didnt officially start smoing untill i was 19....lol but did it every now and then inbetween.. :rasta: