This is a fairly common form of sleeping disorder among medical professionals, police officers, and fireman. This is attributed mostly to people who change their work schedules and sleeping times around frequently. You'll find this often in college students when they're changing semesters and quarters when they get new schedules and can sometimes throw sleep patterns off.

Meaning if you were used to getting up early one semester and then you get to sleep late on another it can throw your sleeping patterns off, which can make you feel disoriented and confused which is the main cause for why people get up and retire late, and are late for their jobs and classes because they're not giving themselves enough time to adjust between schedule changes.

This is why when a job or school schedules changes it's ideal to give yourself adequate time to make the adjustment so that it doesn't throw you off physically, so you're able to wake up and retire at a reasonable time so you can make it to work and school on time.

This is why it's not always wise to constantly change your schedule whenever possible because if you do it too much you're going to confuse yourself on whether you're coming or going. There are some people who's jobs switch their schedules around so much that it can throw someone completely out of synch because the hours start to get rather conflicted when they're coming and going and not making time for other things like having a life or maintaining their priorities outside of their job and school.

This also can happen if you're running between more than one job and school because if you're going to a job during the day and then running to another job at night it can throw you off as well. People are advised to give themselves so much time between things in order to make the full transition into the new schedule or time frame so they're not feeling overwhelmed and stressed out since stress can play a huge thing in work related insomnia. The stress comes from having to make so many drastic changes too fast and at one time.

This is why people get burned out quickly and dealing with the physical things like indigestion and other things because they're pushing themselves too hard and sometimes forcing themselves to do things that isn't even normal and is considered unhealthy.

College students who are like this tending to gain or lose weight because of the stress they're under to switch from one thing to another and not giving themselves a chance to really adjust fully to a schedule or lifestyle change. Even people who work as nurses and doctors occasionally go through this. Because hours are rather strange, and that can throw off the pattern your body has become custom to when to rise and retire and if you interfere with that, it can make you feel weird which can also affect appetite and mental focus and concentration which most people deal with the disorientation of switching things around too fast.