According to the American Academy of Sleep Medicine, most people should sleep between seven and nine hours every night. There are a handful of people with a mutant gene enabling them to function well on only five hours of sleep, but these people are rare exceptions. Most people need to sleep more than that, and sleep deprivation has unpleasant consequences, particularly if it's long-term.
Randy Gardener attempted to prove that people could function without sleep by keeping himself awake for 11 days without the aid of stimulants, but he ended up proving the opposite. By the eleventh day, Gardener was paranoid, moody and suffering from hallucinations. He also lost the ability to perform simple math, like repeatedly subtracting 7 from 100. Far from proving that humans could function without sleep, he proved that people need to sleep.
Researchers have identified several physical and psychological effects of sleep deprivation:
Brain imaging studies have shown the brains of sleep-deprived people pumping energy to the prefrontal cortex to overcome the effects of sleep deprivation. The prefrontal cortex is the part of the brain that governs decision making and controlling one's behavior around others. It gets used a lot, and sleep deprivation forces it to work harder than it should.
Sleep deprivation affects both short- and long-term memory. During sleep, the brain consolidates and interprets events and things people have learned. Doing this enables the formation of long-term memories. Lack of sleep disrupts the process, making it harder to learn new skills or form new memories.
Lack of sleep also damages short-term memory, so a sleep-deprived person has trouble remembering something like a phone number, much less how to do anything complicated.
People who don't get enough sleep have trouble focusing on things. That means they're also less observant than a well-rested person.
After 36 hours of little or no sleep, people lose the ability to plan their activities. They either lose the ability to make decisions altogether or get stuck in ruts doing the same thing over and over. Since a sleep-deprived person can't plan effectively, they fall back on habits, both good and bad. A well-rested person would be able to at least try to curb their bad habits.
Another aspect to the inability of the sleep-deprived is a loss of the ability to correctly gauge risks. This has been seen in late-night poker games. Players lose the ability to make strategic decisions based on the cards they're holding and what they know about their fellow players' cards.
Sleep deprivation causes brain cells to die. One study performed on mice found that 25 percent of certain kinds of brain cells died due to sleep deprivation.
Research has found connections between insomnia and mental illness. Mentally ill people often have trouble sleeping, which exacerbates their symptoms and decreases their ability to control themselves.
Poor sleep reduces activity in the frontal lobes, which are responsible for self-control. On the other hand, it stimulates those parts of the brain that govern automatic behavior and rewards. A recent study showed that people's more restrained and civilized behaviors were impaired by lack of sleep, while their more primal urges and desires were amplified. Sleep deprivation harmed self-control, making it more likely that a person would give in to cravings for their favorite junk food.
Sleep-deprived people were similarly more likely to buy junk food than their well-rested peers were due to impaired decision making abilities.