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Insomnia and emotions have a very close link. In fact, it’s likely that on more than one occasion you woke up grumpy, irritable, or listless after a night when you slept poorly and couldn’t get enough rest.
On average, we spend 25 years of our lives sleeping. It is a long time. And that indicates the enormous importance of sleep, both on a physiological and psychological level. Sleeping less than 6 hours a day can have harmful effects short and long-term, both for our health and for our emotional balance.
Lack of sleep reduces positive emotions
Sleeping not enough affects our emotional state. This was verified by researchers from the Department of Psychology at the Norwegian University of Science and Technology, who analyzed the sleep patterns of 59 people and their reactions the next day.
These people first slept normally in their homes to undergo a series of tests the following morning. Then, for three days, they had to go to bed two hours later and get up an hour earlier than usual. In the morning they performed tests of precision and responsiveness, as well as tests to assess the positive and negative emotions they were experiencing.
The researchers found that when we don’t sleep enough, we respond much faster to stimuli, but we are less attentive and we make more mistakes. In practice, we react faster to compensate the lack of concentration. As a result, we make more mistakes.
Our emotional state also suffers. “Positive feelings scored worse after just one night of reduced sleep, and decreased even more after three nights”, the psychologists wrote. Therefore, they conclude that lack of sleep can become an emotional problem that gets worse quickly.
After a bad night’s sleep we lose neutrality
Not getting enough sleep not only influences our mood, it affects the way our brains process the stimuli we face throughout the day, according to another study conducted at Tel Aviv University.
In this case, the participants performed a series of tests after sleeping as usual and after a sleepless night while the researchers measured their brain activity. One of the tests consisted of asking people to indicate the direction in which a yellow dot was moving on different images that had a positive, negative or neutral emotional valence.
Interestingly, those who slept well were able to identify the direction of the point on the neutral images faster and with greater precision. In contrast, those who didn’t sleep well had difficulty identifying the point on all the images, which means that they were also reacting to neutral ones.
Going through a sleepless night distracted people, activating the amygdala, the emotional control center in the brain that detects the most outstanding signals in the environment, so they assumed neutral stimuli as threatening.
“These results reveal that, without sleep, the mere recognition of what is emotional and what is a neutral event is altered. We can experience similar emotional triggers from all incoming events, even neutral ones, and lose our ability to process more or less important information. This can lead to biased cognitive processing and poor judgment, as well as anxiety”, the researchers concluded. That would explain our irritability when we slept badly.
The insomniac brain
Apparently, when we do not rest enough, the cognitive control of emotion is affected, which is essential to adaptively respond to the environment. In practice, the areas of the prefrontal cortex, which would be in charge of regulating the emotional activation that occurs in the limbic system, stop exercising diligently their control function, so that occurs emotional hyperreactivity. That would explain the deep connection between insomnia and emotions.
Another study conducted at the University of Arizona’s Laboratory of Social, Cognitive and Affective Neuroscience may have the answer to that “disconnection” – or at least part of it. These neuroscientists appreciated that after a sleepless night, people with a more positive mood were those with more compact white matter.
White matter is made up of long, isolated fibers that connect brain cells to gray matter. White matter, therefore, would be what allows our brain to function efficiently and quickly, facilitating speed and connectivity between neurons.
When this connection fails or becomes slower it affects the connections between the different areas of the brain, so that we cannot exercise effectively self-control and the emotional brain is at ease.
Women suffer more the side effects of poor sleep
Interestingly, the link between insomnia and emotions is more intense in women. A study carried out at the Sleep Research Center of the University of South Australia revealed that after 36 hours without sleep we are experiencing a gradual affect on our mood.
Lack of sleep generates depression, anger, confusion and anxiety, accompanied by less energy and exhaustion. However, women were more vulnerable to those changes, experiencing a more depressed mood and increased anxiety after sleep deprivation.
Of course, sleeping is a highly individual process. There are people who need eight hours of sleep every night and others who can rest with less. The most important thing is for everyone to find their balance. You will know it from your mood the next day. If you are in a good mood and alert when you get up it means that your sleeping habits are beneficial. If not, you should rethink your routine, for the sake of your physical health and emotional balance.
Saksvik, I. et. Al. (2020) Mild to moderate partial sleep deprivation is associated with increased impulsivity and decreased positive affect in young adults. Sleep: zsaa078.
Bajaj, S. & Kilgore, D. (2019) Vulnerability to mood degradation during sleep deprivation is influenced by white-matter compactness of the triple-network model. NeuroImage; 202: 116123.
Simon, E. B. et. Al. (2015) Losing Neutrality: The Neural Basis of Impaired Emotional Control without Sleep. Journal of Neuroscience; 35 (38): 13194.
Short, M. A. & Louca, M. (2015) Sleep Deprivation Leads to Mood Deficits in Healthy Adolescents. Sleep Med; 16(8): 987-993.