(Before anything: sorry if that nessage comes accross as insensitive, this is not the purpose. More on this at the end)

Your situation sounds like the textbook description of depression as caused by "mental distortions" from proponents of CBT. Did your wife consult a CBT practitioner, and did this help?

I am in no way trying to say I know the solution to your (past) problems, but CBT is sometimes described in a bit too enthusiastic terms by its proponents, and your story sounds like an opportunity to get anecdotal evidence on how much it might actually work in practice. In particular TEAM-CBT proponents claim to be able to cure depression in a session (and then continue to accompany the person through the innevitable relapses). I love their very data-oriented approach, but find it too good to be 100% true.