Two points, one cultural, one statistical.

The cultural one is that for some reason here in mainstream America, we have become *entitled* to happiness, rather than understanding that we have the freedom to pursue it, which is not the same thing.

Then we (here) also have the idea that shooting a person or people is an acceptable response to infringements upon that happiness, rather than understanding that guns for sport or defense should not be used for offense against people who make you less happy than you think you have the right to be.
Guns for sport, if it's trying to get some of the abundant animals to eat and use the parts of, nothing wrong with that - no waste and no endangering species.
For defense means of your *community* - more people should actually read the second amendment - against an foreign enemy or our own government (really, everybody should reread the second amendment), should we decide that we need to be protected from them.
Even defensive guns are not to defend your personal happiness against anybody at all.

That's why IF someone in the US goes off the deep end, they tend to land in a pool of ammmo with the ability to propel more and more of bigger and bigger caliber at higher and higher velocities with greater and greater accuracy as competition amongst the various shooters escalates.
Also, affluence breeds greater entitlement so it's the white middle-class males doing most of these massacres - so far there has been one Asian and one African alone of all the school shooters (or the movie theater one).

But.
The statistical point is more important, to me.

Much as I like the poster of that long list, that is a long list of crazy people who went crazier, and who were also taking drugs to prevent that. Crazies are already crazy, but still:
How long is the list of crazy people who go crazier WITHOUT the drugs?
How long is the list of crazy people who get LESS crazy WITH the drugs?
I bet both of those are a LOT, LOT longer. What you have then is a relatively few failures for many successes, which is what we'd expect. Nothing works 100% of the time, and if you're already loony, and then the drugs don't work for you, what else can you do but go crazier? And if you're an American, over-entitled and over-armed, would any OTHER way of being crazy even occur to you?

Also:
How long is the list of people we don't know are crazy yet because they aren't in treatment, who go crazier without the drugs?
How long is the list of those last who go crazier even with drugs they get on the black market?
How long is the list of those (now second-to-)last who get *better* with the drugs they get on the black market?

So, before going after the drugs for all their failures, let's remember that they are failing some of a population of high-risk individuals, and figure out how big that proportion actually IS.

After all, almost 100% of hardened criminals smoked pot at some point.    However, since probably closer to 100% of hardened criminals drank breast milk or formula as babies, that datum alone is hardly indicative of anything. You need the other cells in your matrix.