Hi op
Gaming addictions are like a re wiring of the brain for teens, they forget what normal family or human interaction is. They have to go back to basics, he needs to be so bored that he finds a solution to his boredom. He has been over stimulated for such a long time, he needs to power down, hence the sleeping etc.
My son had an addiction to call of duty, it took me 3 months to get him back or rather him coming back to us. It was cold turkey all the way, suddenly his natural personality started to shine through,to the point even he knew he had had a problem. He is much more regulated now, also much older and mature.
Stick with the basics don't pander or promise expensive treats, personally I wouldn't bribe him out of it either, it will give him something to manipulate you with. He may have to go through this stage so his equilibrium starts to right himself.
He's been living in a fantasy on line gaming world, where everything is quicker faster and offers instant gratification, you cannot and should not compete with this.
I'm not sure of the depression diagnosis at the moment, his head is buzzing and he's coming down from an addiction, until he's mostly through this stage, you can't really see what may or may not need treating .
I Imagine that his sleep pattern or lack of it has been all over the place, I'm not surprised he's sleeping so much, it's actually a good sign, it may mean his melatonin levels are probably sorting themselves out.
Keep a close eye on him, keep all boundaries in place and don't engage in any re negotiation with him.
Little things like Joining you all for dinner around a table will help with normality and routine, also good things like board games help too.
He will ignore you at first but if your playing a game and enjoying yourself, over the top laughing and joking etc, his curiosity will get peaked at some point, he may very well join in because he's so bored.
Boredom is a natural state for everyone at some point, he has too experience it.
On a side note if your that worried about self harm etc, quietly make sure there's no ligament points as far as possible in his room, it might be extreme to say this, but i always err on the side of caution.
Keep offering him to join in with the family routine, at some point he will start to come back to you 