It isn't just startups themselves that cause these issues, there's a predisposition. My cofounders way back when could handle the pressure just fine.
I'd recommend anyone who is experiencing mental health issues to talk to a therapist. CBT is good for panic, and psychotherapy is good for anxiety and depression (imo.)
Employment is mostly about taking on the burden of someone else's stress and handling it. When your stress becomes too much the employer hires peers and perhaps gives you some minions to make things better.
If you were never taught how to manage stress and your family hasn't ingrained stoic values into you (because they themselves were never taught them) then the body is going to become overwhelmed, give up and switch into protective mode, also known as burnout, anxiety, depression, breakdowns etc.
Thanks for the insight btw :)