I think it has quite a lot with personalities, because for me and all my NT friends smoking weed is like a different world, because it activates the sensing and feeling bit we don't have that much, but for SFs it should have way less effect as you probably live in this Sensing and Feeling world. I am a beginner in MBTI, but that is my theory. All ISFP when smoked weed with me when I used to smoke weed said that they have no effect, but just feel strange.
Well.. I do have a mild effect with weed.. Sharpened senses and mild hallucinations... But never actually reached the heights that I heard being described by my own friends.. And yes.. I inhale like hell... (Probably bcoz I smoke a lot..) Maybe Nothing to do with personality types though.. May be the weed sensor chip is missing.. just kidding..