Daniel Radcliffe's life changed forever when he was cast as Harry Potter, and that road wasn't always fun or easy. Over the course of 10 years Radcliffe made eight movies as "the boy who lived" and became one of the biggest celebrities in the world. The actor admits that it was difficult to go out in public where he would be recognized, and sometimes he would deal with, what he viewed as constant attention, by applying alcohol. According to Radcliffe...
There is an awareness that I really struggled with, particularly in my late teens when I was going out to places for the first time where you would feel — again, it could have largely been in my head — where you would feel watched when you went into a bar, when you went into a pub. In my case, the quickest way to forget you were being watched was to get very drunk. Then as you get very drunk, you become aware, ‘Oh, people are watching more now because now I’m getting very drunk, so I should probably drink more to ignore that more.’ It can affect your psyche.
While lots of people are famous, and many of them became famous while very young, there's probably nobody in the world who has had a life experience comparable to Daniel Radcliffe. He took on a major film role as a kid and then spent the next decade doing essentially nothing else. The movies were all massive hits, which made Radcliffe a star.
This led to him having difficulty doing simple things, like going out for a drink. He admits that he doesn't even know if he was being watched by everybody else to quite the degree that he felt that he was, but either way, that pressure would get to him, and he relieved the pressure the same way a lot of us do, with drinks.
It doesn't sound like things ever got too out of hand, beyond occasionally getting seriously drunk, but as Radcliffe tells The Off Camera Show, it did effect him mentally. Eventually, he did realize that things needed to change, and with the support of the people around him, he was able to keep things from reaching the point where they truly spiraled out of control. He says the drinking never impacted the work, mostly because he still loved the work and never wanted to quit. He still loves the work and is glad that he played Harry Potter.
Radcliffe himself says that he expects a reboot of Harry Potter will happen someday. Hopefully whoever gets cast in that role doesn't go through quite the overwhelming experience that Daniel Radcliffe did.