There is no proof but there will be signs.
Discussion
And why do you care? Its his life. He is an adult. He is harming nobody. I would think a person using bitcoin as a screen name would understand the concept of privacy
But I also understand the concept of health. And when you are on levels where you need to take drugs to sustain your health form, it has consequences. You agree on that right?
And it is also a part of 'proof of work'.
If done responsibly its not harmful. And why the assumption he is still on if he ever was? He's a large framed dude. He has the structure to do this naturally and retain it.