On my last ship while I was in the Navy I ran, regularly, 20 hour days. This was primarily due to a lack of qualified personnel onboard (we'd lost a few for various admin reason), and we were placed on a program where we were given supplements to assist our schedule. When I left the boat, I was diagnosed with acute clinical depression, anxiety disorder and had panic attacks on a regular basis. Even now, several years later I still have them, something I never had prior to being put on sleep deprivation. The depression is gone, thanks mainly to some serious counseling, but many of the other side effects are still here.