Enough people are on antidepressants that it is ending up in the water supply in measurable amounts.
If that was true, then there would be no need to buy anti-depressants. Just drink some water.

"Not a serious mental disorder" is very relative in 2019. You can expect people to refer to you as the planet Venus and "not have a serious mental disorder."
That is unfortunately quite true. Although it's always kind of been like that. It's just become more noticeable within recent times, because all of the nutjobs now have a voice thanks to the internet.
Although you probably shouldn't bad-mouth yourself.

The things he did is not what a sane person would do but still that's what they concluded. What are your thoughts about that?
Well if we considered everyone who committed a murder was insane. We'd be sending them all to a mental home instead of a prison. Which sounds suspiciously like Batman's arkham asylum to me.

But as for my thoughts on the matter. Maybe serious mental disorder, is just things like hearing a voice telling you to do it, or actually believing you're killing a monster. Simply murdering someone because you feel like it, doesn't count as a mental disorder, even if it's not normal.
I could go into a lot more depth of what I think, until I finally delve into philosophy and end up going way off topic. So I'm going to stop here, and just say, I'm not entirely sure.