Yeah, he should definitely seek help. The MDC is a great resource, so are the chaplains. I found that when life sucked at USNA it was best to go for a run and chat with my friends.
Pills will wreak havoc on his routine at USNA. I was on wellbutrin as part of a tobacco cessation class youngster year. Didn't sleep for 2 days at one point. I realized how much they were messing with my system and cut them out.
Chances are that even if it is something disqualifying (read medical condition not just depression) they will still graduate him with a degree just not a commission.