Synopsis for
Thumbsucker (2005) More at IMDbPro »

Justin is a nerdish teenager (quite normal) still sucking his thumb (why not?) in love with a classmate (not uncommon) and feeling shy, uneasy and with an attention problem. After he has been prescribed some kind of drug from the school doctor, he becomes focused, clear and aware, thinks fast, reads all the time, becomes a sort of genius in the debate contests, wins the school debate state contest, ...and thinks he knows everything, advising his parents on their lives, etc....

A real good movie on awareness, power, and maturity, in the form of a fable... Vincent d'Onofrio and Tilda Swinton, playing the parents, are real good, and Lou Taylor Pucci (playing Justin) does a great job.