Some advice for grad students who want to preserve their mental health:
1) Have an entirely separate life outside of academia. Do not mix the two, maintain a strict separation, and keep all academic relationships strictly professional.
2) Don't think of your advisor as anything other than an employer. They're not a father figure or a mentor or anything like that. You're just cheap labor, and don't forget it.
3) Don't think of you university as a 'place of learning and research' - they've all been corporatized to the hilt, and are basically run on the same lines as any business entity, including the worst aspects of corporate HR.
4) If you do have mental health issues, absolutely never go to anyone like a university-affiliated therapist, etc. If you ever have a dispute with the university, they'll use any such interaction in an effort to discredit you.
5) Fraudulent manipulation of data is more common than not as is dishonest behavior by PIs, and if your data from your own research doesn't agree with their past work, they'll try to prevent it from getting published and otherwise sabotage your progress, so expect that.
6) Academic politics is among the nastiest that exists, and enemies of your PI will also happily sabotage your progress just to make your PI look bad. Even other grad students might try something like this, so trust noone (and see #1).
7) If you have any really brilliant ideas with commercial potential, don't say a word about it to anyone, don't write it down, because the university will claim that it owns all your IP and will demand a percentage of anything you do with it, so keep quiet until you've left the system.
You can learn a lot if you get into the right situation, however. Careful vetting of any prospective research group is important in that respect.