Disturbances of sleep are common. Apart from insomnia, patients may complain of excessive daytime sleepiness, disturbed behavior during night time sleep, the parasomnias or disturbing subjective experiences during sleep and its onset.

Rapid eye movement sleep seems to be the most important part of the sleep cycle for refreshing cognitive processes. Deprivation of rapid eye movement sleep causes tiredness, irritability and impaired judgment.

Types of sleep disorders-

1. Parasomnias.

2. Daytime somnolence.

3. Narcolepsy.

4. Restless leg syndrome.

5. Periodic limb movements.

1. Parasomnias- Automatic behavior that is not recalled may take place during light sleep. Sleep talking and sleep walking are common in normal children.

• Night terrors occur as sudden arousals from deep slow-wave sleep. They are more common in children but may affect adults.

• The sufferer wakes in a state of agitation, screaming and fearful. Occasionally, violent behavior occurs. The agitation may last many minutes.

2. Daytime somnolence- Excessive sleepiness in the day is most commonly due to inadequate night time sleep related to fatigue and poor sleep hygiene, including the excessive use of caffeine and alcohol in the evening.

• Night time sleep may also be disturbed by sleep apnoea, periodic limb movements and restless leg syndrome.

3. Narcolepsy- In narcolepsy there is a familial tendency suggesting an autosomal dominant inheritance with low penetrance. Recurrent bouts of irresistible sleep are experienced, during which the EEG often shows direct entry into rapid eye movement sleep.

• Sufferers tend to fall asleep when eating or talking, not just when under stimulated. The periods of sleep are usually short and the person can be woken relatively easily. He or she usually feels refreshed after waking.

4. Restless leg syndrome- this is a common syndrome, also known as Ekbom's syndrome. Unpleasent sensation in the legs that are ameliorated by moving the legs occur when the patient is tired in the evenings and at the onset of sleep. This condition has a strong familial tendency and can present with daytime somnolence.

5. Periodic limb movements- In this syndrome, sleep is disturbed by repetitive jerky flexion movements of the limbs which occur in the early stages of sleep. The history of abnormal limb movements during sleep is obtained from the patient's bed partner.