Sleep medicine is a medical specialty devoted to the diagnosis and therapy of sleep disturbances and disorders. Over 100 different disorders of sleeping and waking have been identified, grouped in four main categories: problems with falling and staying asleep (insomnia); problems with staying awake (excessive daytime sleepiness); problems with keeping to a regular sleep schedule (sleep rhythm problem); and unusual behaviours during sleep (sleep-disruptive behaviours, e.g. sleep walking). Treatment will vary and depend on the specific sleep disorder but range from medicines, Cognitive Behavioural Therapy, sleep hygiene and sleep routines, and relaxation, meditation and exercise.