Page "Delayed sleep phase disorder" Paragraph 29

DSPD is diagnosed by a clinical interview, actigraphic monitoring and / or a sleep diary kept by the patient for at least three weeks.

When polysomnography is also used, it is primarily for the purpose of ruling out other disorders such as narcolepsy or sleep apnea.

If a person can, on her / his own with just the help of alarm clocks and will-power, adjust to a daytime schedule, the diagnosis is not given.