October 2020 | Reviewed by: Seema Khosla, MD and Andrea Matsumura, MD
What is delayed sleep-wake phase disorder?
Delayed sleep-wake phase disorder (DSP) is a circadian rhythm disorder. It consists of a typical sleep pattern that is “delayed” by two or more hours from societal norms. This delay occurs when your internal sleep clock (circadian rhythm) is shifted later at night and later in the morning. Once sleep occurs, the sleep is generally normal. But the delay leads to a pattern of sleep that is later than what is desired or considered socially acceptable. This pattern can be a problem when it interferes with work or social demands.
If you have DSP, you are likely to prefer late bedtimes and late wake-up times. When left to your own schedule, you are likely to have a normal amount and quality of sleep. It simply occurs at a later time.
One sign of DSP is difficulty falling asleep until late at night. Another sign is having a hard time getting out of bed in the morning for work or school. These signs can make DSP look like insomnia. Also, like insomnia, DSP can impair your alertness and performance during the day. It can lead to excessive sleepiness and fatigue.