Is this an obsessive relationship?

My son has been seeing a girl who has a lot of issues. We have noticed that since seeing her (about a year) that he gets depressed, never talks like he's in love, and when he's not on an outing with her, he is on the cell phone (she gave it to him) for 7 or 8 hours or more. He never wants to go anywhere with his siblings anymore and we have to fuss at him for little things because he can't seem to think for himself. It's almost like he has become her puppet. He is not on drugs or any other substance, but they can't seem to be away from each other at all.