I know you can't be addicted to weed but . . .?

i used to be best friends with this guy last year, and we really drifted after he started smoking weed. i'm generally not against weed, but he smokes it in a lot of qualities and he told me himself he can't not smoke it. i know it's proven you can't be chemically addicted to marijuana, but is there some kind of mental addicted a person can develop? and is there anyway to help him, he used to be such a great guy, and he really changed. it saddens me to see him like this because i really do love him.