And I don't think this is a positive trend. Teens experimenting with weed, alcohol, and so on should not be encouraged but is, or was, just a part of life. Teens being on antidepressants, prescribed stimulants, and so on is rather quite sad.
Pre-antidepressants my life was fantastic on paper: stable job, close friends, good family, strong relationship, perfect health. But none of it mattered, there was no happiness, no sadness, no fulfillment, no contentment, it's hard to convey the total absence of literally any feeling at all toward anything. And I had no other frame of reference so I thought that's just how life was. I even went to years of therapy and that didn't help either. Eight months of antidepressants and I was a different person. I can't tell you how much regret I feel that I could have been happy for all those big important life moments— my first kiss, my first dance, my prom, winning states, graduating college.
I think the term we generally really mean when we say happiness is contentedness. Because that is more a state of being than some temporary sensation.
And far from just a semantic difference, I think this opens up an entirely different life perspective because it's much more about controlling your response to things, particularly those outside your control than it is about pursuing some carrot of happiness that will always slip away as quickly as it comes.
The Stoics referred to this state of mind as apatheia [1]. It's not apathy, which has the connotation of indifference, but rather the freedom from one's emotions so you can guide your life without being pulled in a million different, and oft irrational, ways by emotion.