I think the most negative outcome is psychological/emotional.And this really depends on the contestant. Some people have given up piano simply because of their experiences in competitions. Some people go on to have careers due to competitions. I live in Fort Worth and have seen a good number of the Van Cliburn competitions back to the beginning. (I don't care for it anymore.... been there, done that), and make no mistake, its VERY competitive (the Piano Olympics) and VERY much a celebrated and by the elite social set not unlike horse racing during the Kentucky Derby.No one counts except the winner and the winner no longer counts when the next Van Cliburn Competition rolls around. In my opinion, the only thing worse than losing is winning! The expectations and career demands placed on the winner are simply crushing. Olga Kern seems to be, IMHO, the only winner I can recall who has really been catapulted into international fame and met or exceeded the challenges. But this is extremely rare, IMO. A couple of winners have died early deaths, and I can't but help think "winning" had something to do with it. But most winners have sort of faded into obscurity, not at all what they set out to do i.e. have a big career. Actually, coming in 2nd or 3rd or whatever seems to be more desirable, as silly as that sounds.And I think another negative outcome is that the person entering competition after competition loses sight of why he/she wanted to be a pianist in the first place, since competitions are antithetical to piano playing from the get-go, IMHO. I would say the only way to find out is to enter one that's not a really big deal and see how you feel. I wouldn't over think it, just get your feet wet.