I read a blog post of yours from 2017 about trigger warnings. I am writing a YA mystery/thriller and want to add a note to readers that the book does not glorify abuse/suicide/etc. with the hotline provided. Should I add this to my manuscript? I have gotten different answers from professors and thought it may help to ask an agent their opinion.
Your intent is pure and to be respected.
But let's think about how this looks in the real world.
You're trying to assauge your readers' hesitation on those two hot button topics---but you don't know what drives that hesitation. Is it the mere mention of abuse or suicide? There are readers who don't want to read any book that has those things in it.
Is it the idea that characters dealing with these problem is "glorifying them"?
That's a pretty skewed viewpoint; abuse and suicide happen in real life. Talking about it isn't the same thing as glorifying it. At all.
The one thing you can do is write as honestly as you can about topics that are difficult to talk about. You're not responsible for anything but your own words.
How someone reads them is their responsibility.
As to including any kind of helpful information, the only problem with that is books are in print (we hope) for decades, and information like this can be outdated.
The better place for this is on your website, or in your social media, where you can update it.
Your job is not to manage your readers' expectations.
Your job is to tell the truth as you see it, as honestly as you can.