Take him for a long walk in the sun when you talk to him each day. Exercise will help.

There are adult book clubs that meet regularly at campuses, libraries, book stores, and coffee shops to discuss books and what local authors are working on. Ditto for theater groups. I went to one of former when I was younger than your son and loved it.

Local science museums have adult clubs in various things like Astronomy and other topics and also have volunteer programs.