on season 7 of my spn rewatch and deanβs drinking is first highlighted when he comes back from hell, but it becomes a real problem when cas dies the first time. i donβt think we see him drinking in the mornings until s7, even though he hints at being a functional alcoholic before that. this new escalation is compounded by a few things.
firstly, the fact that casβs betrayal hardens him and he takes it out on amy. he admits as much. he kills her despite the fact that sam trusts her and cares for her, because the person he cared for and trusted turned out to betray him. he says this outright to sam in 7.07 i think this is the first sam/love interest cas/dean parallel we get.
the guilt of this is so heavy on him while heβs lying to sam that he resigns himself to die rather than come to terms with it (which we see in 7.04 defending your life) he knows he did something wrong, he canβt really live with it. something that is markedly different from the general grief and guilt that dean carries from all the other people theyβve lost.
so at this point dean is drinking heavily. heβs using any chance he gets to sneak off to a bar. sam is worried about him, and dean canβt outright admit that itβs grief heβs feeling, but thatβs the root of it.
and then bobby dies and leaves dean his flask, and now dean is drinking 24/7. this lasts up until cas returns in 7.17 and suddenly tapers off, partially also because within 2 episodes they know that bobby is back as a ghost. so dean got both cas and bobby back, even though cas is broken and bobby is still dead, itβs enough to kind of drop the severe alcoholism plotline, for now. obviously we see it again in the future. season 12/13 also features dean drinking heavily after losing cas, but heβs also openly suicidal at this point. and then of course thereβs sam finding dean passed out in a pile of bottles after cas dies in season 15.
so anyway deanβs alcoholism (and general mental health) is always at its worst when he looses cas.
