Having worked at a treatment center, where there was a high proportion of substance abusing/depressed docs and other "wealthy" people, I'd say a lot of it centers around:
1) the *real* reasons some people choose to go into medicine
(clue: if you really think referring to your patients and your role as a care provider as "fat middle aged vaginas" is EVER appropriate and/or if your biggest concern is how much "partying" you'll get to do without ever thinking about why that's such a big deal thing to you and/or if you don't like studying science/medicine... then becoming a doc might not be the most realistic/honest choice, some go into medicine almost entirely to "prove something" to their family or themselves)
2) the *unreal* expectations these same people have about life as a doc
(example: rolling in cash with hotties lining up (btw, women like that are generally known as hookers to the people who have actual relationships that they don't need to purchase) and believing that everyone will see them as SO SMART or SUCH A GREAT PERSON or SO PRESTIGIOUS- in reality, even when you're a doc- surgeon or not- most people will just see you as a person and, if you act like an a**, they'll view you as such regardless of your degree or position- maybe even more so because it seems completely backwards for a doctor to be greedy/immature/shallow when it's a helping/service profession where most expect you to actually care about your patients)
3) Therefore, these unhappy med students aren't: rolling in cash, don't have hotties lining up, have to study a lot, aren't getting the respect they believe they deserve from everyone, and in general- it's just not working out how they thought it would in the fantasy land of pre-med. Some will get honest with themselves and change professions, others will not and they'll most likely become unhappy docs when they realize their $$$ doesn't buy all the things they thought it would. Maybe they end up in treatment and get a reality check then or maybe they just live out their lives trying to feel good about themselves by trying to believe they're better than everyone else for all they "sacrificed" and how smart and impressive they are- even if it's mostly fantasy world stuff bearing no resemblance to what a normal, healthy person would want from life, anyway.
Also, those who view the entire process as something miserable that they have to "get through" and then their "real life" will begin, are probably going to be bitter people when they someday realize that every minute of every day of **8 years** WAS "real life"... that they didn't enjoy because they just wanted to get it over with and move on to something better. Those who take each day as it comes and had the foresight to think about WHY they're really going into medicine, genuinely have a passion for the field- both its material and practice, and try to relate to their patients (every one of them) and focus on the positives of the entire journey along the way (because this IS their 20's and their life happening) will probably be happier at every point, *especially* later as docs b/c they won't view themselves as martyrs who are "owed" something for what they "endured".
Lastly, it's possible that some people either didn't choose or didn't get into a med school that was a good fit. I think that can likely make or break your experience of the entire process. If you go somewhere with intense competition and you hate that- but you decided to go there, anyway (for the "name"), then you're going to be miserable. If you tend to get totally stressed out wanting to make the highest grade possible and you go to a school with grades (including those "HP/P/etc" systems that are really grades by another name) instead of one with P/F only, then you're probably going to be miserable... etc.
If the issue was solely having to study so hard or lack of sleep, they would have faced those same issues at some point before medical school and it certainly wouldn't lead to the level of intensity/drama that you see represented by the posts you were referring to.
For a thread that was started for the sole purpose of being inspiring, this has to be the most depressing thread I've ever read through on this site...
I'm wondering if there are a disproportionate number of dissatisfied med students on SDN because the ones who love med school pretty much don't need or want to read a site like this. Otherwise it sounds like 75-80% of med students are miserable (which might be true... I will soon find out I guess)