According to the National Institute of Neurological Disorder and Stroke (NINDS), hypersomnia is a sleep disorder in which the patient experiences excessive sleepiness during the daytime and/or extremely long periods of nighttime sleep. The side effects of hypersomnia interfere with one's lifestyle by inhibiting his ability to cope with social situations, and they can be just as undesirable as those of insomnia.
Sleeping too much can cause headaches, which scientists believe is linked to the effect of sleep on certain neurotransmitters in the brain, such as serotonin. Too much sleep can disrupt the balance of the chemicals in the brain and cause headaches.
Too much sleep can cause great deals of pressure on the back for extended periods of time, which can lead to back pain.
Researchers have discovered that a side effect of over sleep is diabetes. In a study of 9,000 people, they found that those who sleep more than nine hours per night are 50 percent more likely to contract diabetes than those who sleep seven hours per night.
Studies have proven that people who sleep nine to 10 hours per night are 21 percent likelier to become obese over a six-year time span than people who sleep seven to eight hours nightly, even when food consumption and exercise levels were considered.
The Nurses Health Study of 72,000 women found that women who sleep nine to 1 hours nightly are 38 percent likelier to experience coronary heart disease than women who sleep eight hours every night.
Regular sleep habits are important to recovering from depression, and sleeping too much can worsen the symptoms of depression.
A myriad of studies have proven that people who sleep nine or more hours per night have notably greater death rates than those who sleep seven to eight hours nightly.