Sleep plays an important role in the physical health of people. Sleep deprivation occurs when an individual fails to get enough sleep. The amount of sleep that a person needs varies from one person to another, but on an average most adults need about seven to eight hours of sleep every night in order to feel well-rested and alert. 

Effects of insufficient sleep, on human body are as follows : 

1. Increases the risk of heart disease, kidney disease, high blood pressure, diabetes, and stroke. Sleep deficiency also increases the menace of obesity. One study of teenagers showed that with each hour of sleep lost, the chances of becoming obese went up. Sleep deficiency increases the risk of obesity in other age groups as well. 

2. Sleep helps maintain a balance of the hormones that regulate appetite. Sleep also affects the hormone that controls the blood glucose level and its deficiency may increase the risk for diabetes. 

3. Sleep also supports healthy growth and development. Deep sleep triggers the body to release the hormone that promotes normal growth in children and teens. This hormone also boosts muscle mass and helps repair cells and tissues in children, teens, and adults. Prolonged sleep deficiency can change the way in which the immune system responds. 

4. Sleep disturbance can also be an indication of other underlying medical conditions or psychological disorders. It may, for instance, be a symptom of Anxiety or Mood Disorder. Furthermore, sleep disturbance that is chronic or severe can bring on or exacerbate serious psychological disorders.