No offense, but that would be a terrible answer. IF you really, really want to be honest, say you had medical issues, but that it is all fine now. No interviewer will dig deeper here, as it would be plain illegal to do so. Still, I think there are better answers than that. I'm sure the OP did SOMETHING in the last three years. Maybe you traveled abroad a bit, read a few books, so just say you took some time to grow as a person, whatever. It's not really lying if there is some truth in it.
