The goal of this pilot observational study is to assess the ability of continuous 'home' EEG to accurately diagnose Narcolepsy in children and young people with hypersomnia. The main question[s]it aims to answer are:

• can ambulatory home monitoring using a Dreem headband with a 'life as usual' unrestricted protocol allow accurate diagnosis of Narcolepsy, compared to gold standard in-patient PSG and MSLT
• which EEG derived sleep parameters and study duration yield most diagnostic accuracy

Participants undergoing investigation for hypersomnia will additionally be asked to wear a Dream Headband at night for weeknights, then continuously for 48 hours over the weekend. The data from the headband will then be analysed to see if it can predict the results of the polysomnography and MSLT that form routine clinical care.

Inclusion Criteria:

• Participants already under investigation within GSTT children and adult sleep service for hypersomnolence
• Age 12 to 25 years of age at recruitment
• Participants able to understand patient information (information including DH instructions written only in English for this initial observational study) and who can provide written informed consent or assent.

Exclusion Criteria:

• Any physician diagnosed sleep disorder (e.g. sleep apnea)
• Any physician diagnosed medical or psychiatric disorder that could explain their excessive daytime sleepiness
• Regular use of either prescribed or recreational medication that affects sleep
• Participation in another concurrent research study

The study population will comprise children and young adults seen in the hypersomnia clinics of the LifeSpan sleep service at Guys and St Thomas' Hospital and The Evelina London Children's Hospital.