Help with a friend?

Not really sure if this should go here.

A good friend IRL (who's name I won't mention) keeps asking me for help about a voice he keeps hearing. He tells me it's giving him suicidal thoughts, and is trying to hurt him. I've suggested a lot of things to him, I asked him has he tried to communicate with the voice, but he says it doesn't help much. This is a bit vague, but has anyone any other suggestions on what I could try to do.

He said to me that he's fairly sure it's a psychological problem, but when he went to get it checked no one could help him. Not really much else I can say.

if it's psychological, it's likely he's "sure" it's not..