I've quit two jobs due to boredom combined with poor management. The first time was only a few years out of college and I quit due to sheer boredom, no stress.
The second time the job was taking a serious toll on my health, but it was such a slow buildup I didn't realize how bad it had gotten. Everything had been outsourced (except me) and nothing was happening. I couldn't get any work done even if I wanted to. Exec meetings were hell - "why isn't this done???" Ummm, because I can't get anyone to do anything and everyone I knew who could do it has been let go.
I knew I was completely screwed when I started staying up until 3 or 4 in the morning. The only reason I was staying up was because I knew the moment I woke up, the hell would resume. The longer I stayed up, the further away the next day was. And I started work at 6am. Normally a pretty healthy guy and I was at the doctor at least 5 times for various ailments that year.
I quit, they begged me to stay after dangling a carrot, and I almost cracked up during that 8 month window. Got the carrot, quit again, told them forcefully to not dangle another carrot because I am bleeping done.
It messed me up pretty good. It's been seven months and I'm still working on some of the personal issues, but I'm a helluva lot better than I was before.