Cannabis can be used as a medicine, and it can be used for the purpose of leaving our current state of consciousness—our present mindset, if you like. It can be used as a euphoriant, to make people feel happier. So it clearly can be used for people to relax in a social setting. These are some of the ways it's used, as you and I would say, probably not as a medicine.
But Dr. Shackelford is quite correct. People will often say they are using it recreationally, but clearly they're using it for pathological conditions like anxiety disorders.