Here's something I have been discussing with my students, which I would like to share.
The Buddy System.* You agree with another student to be their buddy and vice versa. It's a contract. You keep an eye on this person, and they do the same to you. Ideally they are someone you see online regularly, like a study partner. If you see your buddy starting to slump, with depression, stress or anxiety, you give them a nudge. "Hey mate, you're not yourself, you need to speak to the doc" "Hey mate, I know I'm nagging, but seriously..."
Your buddy does the same to you. If you are slumping, they get to prod you.
I don't think any depressed person likes to be nagged to see the doc, but these are special times. That's why you make the contract beforehand. "We agree to mutually nag if necessary. We'll try and ring the doc if we get nagged." Set the ground rules now.
I've suggested this because not all my students have good relationships with their families, and even if they did, they'd probably hide how bad they were from their families. Some are living alone and may be spending weeks without any face to face human interaction beyond trying to stand 2m away from a checkout person. I am genuinely more worried about a student losing their life from depression than covid at this time. It might not be a brilliant solution, but it's better than nothing and the students have reacted positively to this suggestion.
So if you think this might work for you, even if you are not a student, maybe consider getting a buddy of your own.
* In scuba diving, you never dive alone, as it can be very dangerous. Instead, you should have a diving "buddy" who you dive with each time. The buddy looks out for you, and you look out for them. Diving with a buddy saves lives.