Batman has always been known as a beacon for hope in Gotham City, no matter the medium. With each new supervillain that threatens the city's residents, Batman and his allies have been there to stop them. However, in certain mediums, specifically films, villains like the Joker and Riddler have noted that Batman is just as insane as the people he fights. While it seems like a way to get into his head, one theory believes there's some validity to the claim.
According to a Reddit theory by slugboi, it's believed that Bruce Wayne, unable to cope with the loss of his parents, developed the Batman persona in his mind and is a patient of Arkham Asylum. Therefore, the villains he faces are actually doctors and caretakers sent to treat him. While this theory has been explored from the lens of the comics, the films actually provide some curious evidence that makes the theory even more enjoyable.
The Tim Burton films paint a unique picture, representing Bruce fully settled into his false reality. Gotham City is gloomy and dark, similar to his views on the city that took his parents. He also broods in the darkness, possibly representing his time in solitary due to a violent streak exemplified in these films. Villains like the Joker could have been a doctor treating him due to his knowledge of chemicals and the Waynes' murders, making him the "cause" of their death. However, the Penguin and Catwoman could be more patients who see him as an equal.
After more treatments, Bruce's outlook is less dark, as shown by the neon Gotham from the Joel Schumacher films. The theory also believes that Dr. Edward Nigma is another therapist sent to treat Bruce who twists his words into riddles, creating the Riddler in his mind. This could also extend to characters like Mr. Freeze and Poison Ivy, who are also doctors that could represent different treatment methods, one warm and the other cold. But when Bruce gets out of line, a burly orderly similar to Bane would be the only one capable of handling him.
The theory leads into the Nolan films with Dr. Jonathan Crane, who used many methods to help Bruce. But to Bruce, these methods, which likely make him face his fears, only created the Scarecrow. But with therapy and mental health education advancing, the methods have since become more grounded, changing the world to the one seen in Nolan's films. If true, Bruce's sacrifice in The Dark Knight Rises may allude to an escape attempt from Arkham.
Ultimately, there are no facts tied to the theory. But unlike comics, games and animation, the movie universe lends itself best to the idea. The changing iterations represent the changing psyche of a victim like Bruce and the villains show how hard the system has tried to rehabilitate him. So while there are no grounds to say the theory is true, it's a unique way to connect decades of Batman films.