Hi Denmother,
I'd definitely keep a watchful eye. If you can get him to see someone, I'd say that would be best. Perhaps if he goes, even if he does not talk, he will eventually see that there is help for him available so when he is ready he will know. It's a hard situation. I've been in a similar situation where I had to be hypervigilent and stay in tune with son so I could call 911 in time but not too early. I hope your situation does not get to that situation. Maybe just let him know you're there if he ever needs to talk. And be his safe person.

Zoloft made my son more suicidal (and resulted in an attempt) and is not recommended for teens. There are a lot of different antidepressants if you can get him to take another one. It's so hard when they refuse help.

Best of luck to you. Please keep us posted.