How a Lack of Sleep Affects Your Brain – and Personality

In 1959, Peter Tripp , a popular New York DJ, pledged to stay awake for 200 hours for charity while continuing to host his radio show.

Studies into sleep deprivation were rare at the time so no one knew what to expect. This made it a major event, not only for Tripp’s millions of listeners, but also for the scientific community.

The subsequent impact of the “wakeathon” on Tripp’s mind was far more dramatic than anyone had expected. The personality of a man normally described as cheerful and upbeat appeared to significantly change as time went by. By the third day he had become highly irritable, cursing and insulting even his closest friends. Towards the end of his endeavour, he began to hallucinate and exhibit paranoid behaviours.

But despite the concerns of the doctors monitoring him (and with the help of the stimulants they gave him), he persisted and finally went to bed after 201 hours of continuous wake time.

Modern laboratory studies have replicated some of the behaviours seen in Tripp as a consequence of sleep loss. Sleep deprivation or prolonged restricted sleep results in increasing irritability, worsening mood, and feelings of depression, anger, and anxiety. Some argue that sleep loss leads to heightened emotional reactivity.

Tired and emotional

Much like Tripp, who lashed out at his friends at the smallest inconvenience, sleep deprived participants in one study experienced greater stress and anger than rested control participants when asked to complete a simple cognitive test.

Brain imaging methods reveal why sleep deprivation can lead to irrational emotional responses. The amygdala , an area deep in the brain, is our emotional control centre. When sleep deprived participants were shown emotionally negative images , activity levels in the amygdala were as much as 60% higher than levels in those who were rested.

The researchers also looked at how different brain areas were connected in these participants. They found that sleep deprivation had disrupted the connection between the amygdala and the medial prefrontal cortex . This was a critical insight as the the medial prefrontal cortex itself regulates amygdala function. Sleep deprivation appears to cause the amygdala to overreact to negative stimuli because it becomes disconnected from brain areas that normally moderate its response.

Sleepless in Las Vegas

Casino owners have known for years that tired gamblers make risky decisions . The bright lights, noise, and lack of windows are designed to stop you from noticing the passage of time.

In 2011, researchers at Duke University asked participants in a gambling experiment to improve each of several gambles. They could choose to do this by increasing the size of the highest possible gain, decreasing the size of the worst loss, or improving the probability of winning. When participants had been deprived of sleep for just one night, they started do make fewer decisions that avoided loss, and more decisions that maximised potential gain. In other words, sleep deprivation made their gambles riskier and more optimistic. This change in risk taking behaviour was accompanied by changes in activity in brain areas that evaluate negative and positive outcomes.

Sleeping to learn

Another area of the brain that suffers dramatically from sleep deprivation is the hippocampus . This is a region critical for the storing of new memories. When people are deprived of sleep for even one night, their ability to memorise new information drops significantly. This was shown in one study to be due to an impairment in the hippocampus caused by sleep deprivation. When memorising a set of pictures, sleep deprived participants showed less activation in the hippocampus compared to rested participants. This deficit in the hippocampus could be caused by sleep deprivation reducing its ability to write in new information.