In this theory, Dean lives in an abusive household with Sam. Both his parents neglect him, they mostly focus their attention on Sam. One night, John had beaten Dean so badly that Dean had gone into a coma.
In Dean's coma, he was reliving his life, but he added the supernatural to be like the monsters that his parents are.
Dean was angry, in his dream, he had Mary killed by Yellow eyes, she would always burn him with a lighter if he did anything bad or if was just doing his homework or watching tv.
Dean made Sam go to Stanford because Dean knows his brother will be more successful than him, but Dean worries since John also beats Sam that John could eventually kill him.
Dean's coma dream, it's him fighting back the monsters, he is currently fighting.
The werewolves represent depression, they lurk in the night, the darkness hiding their true form.
Vampires represent PTSD, they are eternal beings, they have lived through horrific times. Dean suffers from PTSD, from John and Mary hurting him so badly that it has stayed in his memory.
Vengeful spirits represent anxiety The spirits are anxious when Dean and Sam figure out why they can't go to certain place, it's either where they have died or have killed someone linked to them. The woman of white, she was anxious because Sam had to get her home where she had killed her children and her children's spirits took her since they were waiting for her.
Dean, when he goes to school or Bobby's, he feels calm, relaxed, safe, but when he has to go home, he gets anxious, has a panic attack, he gets worked up to the point he can't even breathe.
Demons represent Panic disorder, they are cunning, evil, manipulative and could just appear and possess somebody. Dean is always paranoid, he loses sleep because he fears his parents will barge into his room anytime and hurt him. Due to this, Dean has insomnia because of his panic disorder.
After Dean has woken up from his 15 year coma, Sam was killed at age 22. Sam came home from Stanford to see if his brother would wake up. That night Sam and John had gotten into an argument which had led John to killing Sam by blunt force trauma by hitting him his barbed wire baseball bat. Bobby had passed away after having a heart attack, Cas was killed in a drunk driving accident.
Dean had went home to his parents, they were both shocked to see him alive and well, but they were in for a treat when Dean lifted up his gun and shot them both in the head. He had used the colt, he walked to his parents' dead bodies.
Dean: See you evil black eyed bastards in hell.