Causes of sleep disorders are varied and range from serious neurological problems to simple nightmares. Sleep disorder mean any difference in the normal sleep pattern that can be sleeplessness, oversleep or intermittent sleep behaviors. Persistent sleep disorder is considered to be a problem since it affects the daily living pattern and can lead to severe impairments in body and mind. Sleep disorder can be categorized into dysomnias ,parasomnias and others, based on the symptoms of the sleep disorder. Some of the common sleep disorder include insomnia,bruxism,sleep apnea,night walking,and snoring. The causes behind sleep disorder are very significant since the treatments for the sleep disorders are focused on the cure of underlying cause.