People who work on the night shift are more likely to develop shift work disorder. The reason for this is that their shifts are irregular. People who are working shifts that are two hours apart tend to wake up feeling tired and drowsy. These people tend to experience insomnia while sleeping as well as drowsiness while awake. Their total sleep time must be reduced by one to four hours per night. To be diagnosed with shift work disorder, patients must experience these symptoms for three months or more. Their symptoms cannot be caused by any other medical condition or medication. The doctor may require the patient to keep a sleep diary for a few weeks to accurately determine their symptoms. Once they have been properly diagnosed, they can begin seeking treatment.

While the symptoms of shift work disorder are common among workers, the degree of impairment varies from person to person. Symptoms of the disorder vary, while evening shift workers may experience less severe symptoms than those working on the early shifts. The level of daytime performance impairment can also vary. Some people can gradually adjust to sleeping during the day and working during the night. In any case, environmental factors also contribute to the sleep loss. Shift workers should schedule days off between shifts and take regular breaks.

In addition to the physical symptoms, patients with shift work disorder should have significant sleep problems. Insomnia and excessive sleepiness are symptoms of shift work sleep disorder and must be associated with a work schedule. The symptoms must have lasted for three months or longer. The disorder can be confirmed through sleep recordings, actigraphy monitoring, or sleep logs. These symptoms can cause impairment of social functioning, and are difficult to explain by any other disorder.