How do delayed sleep-wake phase disorder and advanced sleep-wake phase disorder differ?

Delayed sleep-wake phase disorder and advanced sleep-wake phase disorder are fundamentally different in the timing of sleep onset. In delayed sleep-wake phase disorder, individuals typically have trouble falling asleep until late at night and may wake up later in the morning, resulting in a sleep schedule that is shifted later than the societal norm. This can cause significant challenges for those whose schedules require them to wake up early.

In contrast, advanced sleep-wake phase disorder is characterized by individuals who fall asleep early in the evening and wake up very early in the morning. People with this disorder often find themselves becoming tired much earlier in the day, leading to a sleep schedule that is much earlier than what is typical or desired.

Understanding these differences in sleep timing is crucial for diagnosis and treatment, as it helps in developing appropriate interventions tailored to the individual's specific sleep challenges. Other aspects such as duration of sleep, age of the individual, and physical symptoms may have their relevance, but the primary distinction lies in when these individuals actually go to sleep and wake up, which directly relates to their circadian rhythms and behaviors.