Software developer here.

I'm not sure how much my "head-incidents" have impacted the ability to do my job, but I will say that for me personally, it was better to take a light and steady workload rather than quitting my job or going on disability.

I have a phenomenal developer position that allows me to work my own hours and at my own pace (within reason). So, if I feel terrible during the day (which is every day!), I work at night. If I can pad 4-5 extra days into an estimate, I do it.
Basically, I game the system as much as I can to fit the job around my condition and not the other way around. I'm sure these actions stagnate my career growth, but I'm hesitant to advance until I start feeling better again...if I ever start feeling better again.

BTW, PCS or not, I never want to change code. Then again, breaking something is self-preservation as you need someone to fix the mistake. So, it's not all a bad thing. Then again, my company is dysfunctional; so who knows.