Totally agree that we can't take Trump at his word, but the man has been on camera for decades and there is no footage of him drunk. I don't believe that Trump has the self-control to hide a drinking habit.

Also I believe Trump's #1 motivator is narcissism. He may not have cared that his brother died, but he did see himself in his brother. He saw the devastating results of lifelong alcohol abuse and committed himself to avoiding it.