What's the best way to ask how someone is feeling if they have chronic severe anxiety and depression?

[rileynexttime]

I have a relative with whom I mainly have only telephone contact.

Of course I want to know how he is but I can imagine how tedious it must be being asked how are you/how are you doing/how's things.

And all he can do is tell me how bad he feels, and who would want to dwell on that.

We do chat generally so perhaps I should concentrate on that and avoid asking him how he's doing .
Any advice ? Particularly from people who are suffering.

Thanks @Convincemebob ,i did acknowledge to him that it might be hard asking how he is.
He's quite non specific and doesn't say a great deal.

My friend with mental health issues prefers me to ask a less specific, more upbeat eg 'How's things, what have you been up to?' As opposed to 'how are you?

@Ariela thank you ,I shall follow that advice.

"What have you been up to since we last talked?"
"How did x go?"

Open questions that let him decide whether or not he feels like talking about it.