Yes, my first thought is Robin Williams. With that argument, none of us would think he had "any reason" to be depressed.
However, with regard to CTE, depression, suicide, it's probably very hard to say for sure, thought it may become much clearer with more data. Of course there are many factors that can contribute to depression that are unrelated to specific traumas that someone might also have, but we pretty much know that these type of injuries have caused some shocking behavior in people later in life, that had not previously manifested.
Plenty of wives of retired players, and the players themselves, talking about the post-career difficulties--chronic pain, unpredictable mood swings, even violence from those that had never been violent outside of the game.
