Since he will read, I would get him
books on the topic and once he educates himself on this, he may see the need to get a professional opinion and help. He shouldn't assume that this is what he has. People with severe depression experience no pleasure out of life, and I feel there is a fine line between the two. Don't fight him on this, get him the books, and I truly feel the more he learns the more open he will be to help.