My theory is that there is NO direct correlation between drugs like cannabis or LSD and creativity.
I know some talented people, experiences when I was young was watching friends "stoned"/"high" but talking utter crap! The next day after the trip (without fail) these already smart people "think" they have said or done something profound, but they never did!
Days later, their own creative genius is pushed on a search to find out what they said or did that was so profound/creative. Sometimes they do something amazing, but most of the time they don't!
When I was 20 at university (I'm in my 30s now) a friend of mine took cannabis and LSD for the first time. It was not something I did, not because of any moral high ground, but because it also kinda scared me. During the nightout he started to act really strange, bad trip everyone assumed. That weekend (the day after) his mum called asking us all what he had taken, he had been sectioned under the mental health act. It turned out his family had a history of mental health problems. He was sectioned for almost 2 years and never finished Uni.