This does sound like depression, and not something we should be trying to treat on the Internet. If it is, it can be genetic – if your not so predisposed yourself – you can almost be part of the problem, because it’s hard to be sensitive to feelings you know nothing of.
He needs a doctor, but you need to get a handle on if this might not be something coming from his Mom or Dad. You and your wife need to spend time talking to his doctor together. These people kill themselves when it’s bad, so I’d not waste any time. Ultimately for them it is sink or swim – he’s got to be put on his own, but how that program is laid on him can be life threatening and I’d leave it up to a doc. The big problem they have in working with depressives is that they’ve got to get them to understand that it’s just the way it is, and unless they want to stay doped on downers all the time, they’ll just have to learn to deal with it – That is pretty depressing.

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"The object of life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane."
Marcus Aurelius