My HPPD was caused by cannabis. I had used psychedelics previously (about 5 times) and always had a pleasant trip. I smoked cannabis one night and it was like a switch flipped in my brain. I experienced (and still experience) visual snow, afterimages, closed eye visuals, halos around light and perhaps more. I don't get trails or colored patterns on walls.
My visuals are less intense than most on here. I would say that my visuals/HPPD are a 2 or 3 on a scale of 1-10. (10 being the highest) I have still experienced anxiety, DP/DR, and depression. I'm pretty sure that marijuana caused the visual phenomenon I see everyday.