People with shift work disorder can have trouble falling asleep, or staying asleep for as long as their bodies require. They often wake up after just a few hours, or at least before sleeping a full seven to nine hours in a 24-hour period.
In other words, shift work disorder can look like insomnia. The difference between the two is that shift work disorder is directly linked to a person’s work schedule. If a person with shift work disorder were to regain a consistent, regular daytime schedule, their symptoms of insomnia would disappear.
Insomnia, on the other hand, can have many causes (biology, health conditions, poor sleep habits, anxiety, life transitions, medication use…). If you have insomnia, you’re more likely to have trouble with your shift schedule, since preexisting sleep disorders (like insomnia or sleep apnea) can make people more likely to develop shift work disorder.
Think about how you slept during periods in life when you didn’t work shifts. Did you sleep well? If so, it’s a good indication that your shifts are the cause of your sleep problems. In that case, look at sleep advice for shift workers. If your symptoms don’t improve with these steps, it’s a good idea to talk to your doctor.
Source: National Sleep Foundation