As a seasoned Psychiatrist, he ought to know the signs but few can doctor themselves. Listen to the tone of this post: And Death Shall Have Its Dominion
Maybe he should not have retired, but that's what Brits do. It's their culture, to be pensioners. His post-retirement career, as commenter and thinker, has been a fine contribution to the world.
I know what he needs, and it's not pills. He needs to get to the gym and to begin working out hard. Rage, rage....One hour of intense physical effort daily is good for attitude and mental health, and fends off the feeling of aging along with some of its physical effects.
Pic is the gym at our hotel last month in Puerto de la Cruz after we disembarked: the comfortable Hotel Botanico. After we hiked all over town for four hours, I spent a "relaxing" hour and a half in there before dinner. Nice gym. No gym music.