[note: downvote this post if you disagree with this being an unpopular opinion and vice versa if you upvote, you are saying it is a popular one] Every time somebody posts a negative comment about drug use on lemmy, they immediately get downvoted, and a lot of (mostly crackpot) arguments are offered why drugs are actually fantastic, and only corrupt or suppressive governments prohibit it. Medical arguments are swiped aside, and anecdotal “evidence” is provided to point out why drugs are great. The reality is: no recreational drug (alcohol, cannabis, design drugs, mushrooms,…) exists, that is safe for everyone, or that has no detrimental side effects. In addition, people that refrain completely from taking ANY drug usually lead healthier, more balanced and happier lives.
I suppose you should really be clear on what you mean by drug. Tylenol is the one I first thought of when I read the title. It causes liver failure if you take more than the prescribed dose, and would never be approved for sale if it was proposed under current regulations.
Cannabis and mushrooms are a bit stickier. Yes, smoking cannabis can cause significant mental health problems, but not fer everyone, and not all the time (except smoking it can cause lung cancer). Mushrooms are even trickier, as we currently don’t even know what the mechanisms are for it’s effects and what’s more, there was a study being done on ecstasy and psilocybin, but it was run by pseudo-scientific quacks that were all religious about it. So (IIRC) ten years of research turned out to be pretty much useless; however, there are some things we can try to suss out from that steaming shit-pile: drugs like mushrooms and ecstasy effect different people differently. All human brains are wired differently, and it seems that this fact make itself known when studying certain drugs.
Long story short: you can’t generalize a lot of things because the effects vary so much from person to person. Some things you can: like tylenol will destroy your liver and kill you if you take too much, but cannabis might cause you to become overly paranoid and may lead to schizophrenia but, not for everyone. We can’t really say anything about mushrooms and ecstasy right now because that knowledge has been inadvertently locked away by religious freaks.