I do, but I have done everything so its hard to tell, I started doing drugs not so long ago, maybe when I was 18, now im 22, started with weed but now have done almost everything, lsd, mdma, oxycodone, benzos, etc etc... even though I have taken breaks as long as 6 months from drugs and nowadays mostly wait at least 1 month between drug usage (smoking weed, drinking alcohol) I do notice certain things, like for example, when I get drunk now, the next day I forget a LOT of things, while before when I started drinking, I could get blasted and I would never forget anything I did, I have noticed too that I forget things much more often now, and I notice sometimes that I cant recall the right words or speak as fluently, I still speak super fluently and with good vocabulary but the difference is notable to me, I also developed hellish anxiety and panic attacks after a couple of mdma usages and a bad trip with mdma which got better after general drug abstinence, in general I feel MDMA is what has caused the most damage even though ive eaten less than 15-20 pills max in my life, followed by alcohol and benzos, I have gotten drunk too many times and that definetly isnt good for you, its hard to tell really, I do feel they have had a negative effect, and its insidious and you dont notice really, but to be fair its hard to tell, minor things like these I think most drug users have even if they dont notice off the bat, but severe clear impairment is rare, even in hardcore users, of course further abuse will cause further deterioraton and thats why I have started cutting back on my use as much as possible, I try to leave 1 month now between usages of any drug, including coffee or weed or anything, and I exercise a lot and eat a healthy diet, try to avoid stress, I used to use supplements and nootropics for brain recovery buy I never saw a difference so I stopped wasting money on them.