The man had been ripped off by the press and its media pet, Edison....can't blame him for being depressed.
Don't blame him at all. His problems certainly got worse when his fortunes went south, but he had a many of these psychological issues and eccentricities his whole life.
A mind that can create an entire schematic of complicated machinery and mentally test it without building it and without even putting any of it to paper, can also probably create some pretty formidable and realistic demons for its self.