What do you think about the story of this movie? Do you think he was an actual inmate and they were just going along with his role playing game, or did they actually drug him and made him think that he was an actual inmate in the asylum

I had arguments with my family about the plot to this movie, and I personally am convinced that Dicaprio was an actual inmate taking part in an enormous role-playing game to attempt to get him to acknowledge who he really was.
there was lots of proof of this throughout the movie, but most of it is only noticeable if you watch it a second time. an example of such is when he's questioning the nurses, and they all laugh at him when he asks "have you seen anything unusual recently", which to them is ironic because it is being asked by an inmate acting as a detective.
also, there is a lot of symbolism in the film. fire is symbolic of illusion, and fire is present in all of the scenes with hallucinations (like his wife & daughter randomly appearing in front of an exploding car). water is symbolic of reality, like in the flashback of his wife murdering his children, there was a pond. he also says at the very beginning of the movie that he hates water, which is a clue to the fact that he is avoiding reality.
my parents have the opposite opinion to me, and think it was all a set-up to make him think he was insane, which goes to show that not many people are clear on the actual plot of the film