What is it really like to be a Mormon missionary? ?

Anyone out there who used to be a Mormon missionary, and isn't afraid to tell the honest truth about what its like? My little brother is a missionary, and I am scared for him. He never had a problem with mental health, but his missionary president made him see a psychiatrist because his companion said he said "inappropriate remarks". He won't go into further detail. After he went, the psychiatrist gave him Aderrall for ADD, which is a schedule 2 med meaning it is as addictive as legal meds get, and is "nearly identical to cocaine". He would have never taken something like that before! I have heard some really bad things about how they treat the missionaries, I am also scared that they are subtly brainwashing him, though cutting off family ties, and making him constantly feel guilty about himself and that the only way to be better is to follow what they say exactly. I just want some more, HONEST opinions, please.