I was the youngest person in my primary cohort, and one of the youngest people in my secondary cohort. My primary field is also not one that normally accepts people straight out of undergrad. I'm doing just fine

I had the same fears, but if they accepted you it's because they thought you had an appropriate background. Do the reading, take your time and build some confidence.
As for socializing…that was different. I did hang out with the next oldest person in my cohort, but she had a habit of reminding me how young I was (among other undesirable traits) so we don't hang out much anymore. The other people in my program didn't really have the same recreational interests as me when I was just 22 - so while I would definitely say we were friends and I am still friendly with them all, and we got together for studying and at each other's houses, I sought out a base of friends outside my cohort to party with. The master's students at my institution were closer in age and more diverse racially, so I was able to find some peers who still wanted to party the way I did my first couple years here. Most of my friends are still master's students who are outside of my cohort, but closer in age to me. (Not as much partying, though. Mostly we study together, and chill out.)
Jealousy wasn't really a problem, except from the one student who kept reminding me how much of a "baby" I am (really, she was only 3 years older than me, and everyone else in the program was older than her). All of the other students were friendly and welcoming and treated me like an equal.
I will say, Ekans is right about the grapevine distorting things. I was never very forthcoming with my age - I would only share if people asked me - but somehow me being 22 and coming straight from undergrad managed to mutate into me being a child prodigy who was a 19-year-old doctoral student. (Seriously. An MPH student I did not know very well asked my name, and when I told her, another MPH student who I knew as an acquaintance told her that I was only 19 and a child prodigy. I have no idea where she got that from. This was also my second or third year in the program, lol.)
Edited by juilletmercredi, 09 April 2012 - 03:15 AM.