The mystery of sleep

No-one knows why we sleep or exactly when they fall asleep. Why we dream and why dreams can be so bizarre are also mysteries. However, we do know everyone gets stressed if they don't get enough of it. Loss of sleep can lead to anxiety disorders and insomnia and patients become more anxious if they dwell on their condition.

Helping people with disorders that impact on sleep is the profession of Dr Delwyn Bartlett. She is a sleep psychologist from the Woolcock Institute of Medical Research.