I think the problem with child stars is that they start their careers at a very young age, gain a lot of popularity among the younger generations, and then they hit their late teenage years. At that age, around 18-19, two things come into play --- 1) they're not young enough to carry the roles they once played as child stars and 2) they are now wanting something bigger and better. In both situations, fame has got to their head. They want to move to the real Hollywood industry and take up adult, and they think that they will be get the same praise and recognition they got as children. Problem is, there are not enough roles available for actors of that age group. Aside from a few movies, very few have significant roles for youngsters in that age group. Even if they do, they are mostly side roles and not as significant to the plot. Also, these child stars are usually used to acting in comic roles, and not all movies in Hollywood are comedies. At this time, I'm guessing, they feel lost and unwanted. All the popularity and fame they once head is gone, or even if it isn't, its going downhill. In low times, they start heading down the wrong path --- I'm sure there's also a lot of pressure on them, from family, friends, fans, and themselves. Of course it isn't right that they resort to such things and become drug addicts, but its apparent that this is a common path for many of them. For those who stick it out at this age, make it out big later as successful Hollywood actors/actresses. For those that don't, they occasionally end up on the news for being in one rehab center or another. Specifically speaking for Miley Cyrus, I think she's already transitioning her way into the adult world of Hollywood with her last movie - The Last Song. Whether or not things will work out for her, we'll have to wait to find out.
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