How do I know he's not depressed? Well first of all, I know him pretty well. And I have previously worked as an assessing clinician in a crisis team, so I do know the general signs to look out for.... So there could be a small chance that I'm wrong and that he's pretending that he's not depressed and that he's fine, to save face. However there is a much greater chance that I'm right and he's not depressed based off my observations along with the questions that he was asking me when he was applying for his benefits.
Obviously that's not the case for everyone and the majority of those who are claiming are genuinely unwell/unable to work. However there are chancers, and growing up in a community like I did, where generations of families would struggle to find one employed family member between them, you'd know that.
But i guess that you're inferring that you're right and that the man that you don't know from Adam, is genuinely depressed and he did genuinely have a bad back for all those years preventing him from working and I'm wrong? OK.