Sleep is serious business, or at least it should be. In fact, some people get very irritated when they can't sleep or are awakened during sleep. The curious aspect is that it is not a "conscious" anger, but a profound malaise on a visceral level. Finally, now science explains what happens in their brains: Researchers at the Johns Hopkins University School of Medicine have found that interrupting sleep has a negative effect on mood.
Fewer hours in a row is better than more hours with frequent awakenings
The researchers recruited 62 healthy people and divided them into three experimental sleep groups. The first group could sleep for three nights without interruption, the second had to go to bed later during the three nights, and a third group was awakened eight times during the night. The goal was to find out how these three conditions would affect mood the next day.
In this way, the researchers found that during the first night, both people who had fallen asleep late as well as those who were awakened several times showed a worsening of the mood, they felt more irritable and angry.
But starting on the second night, a change took place. People who fell asleep late showed a 12% improvement in mood compared to the first day, while those who were awakened several times during the night showed a 31% worsening. These results were also maintained on the third day.
Why is it so harmful to wake up often?
Researchers note that our bodies can get used to sleep less, but sleep fragmentation is very bad for our mood. In fact, we must remember that during sleep a part of our brain remains active, eliminating the waste products of the metabolism and reordering the experiences of the day in the memory. However, the areas we use the most while we are awake rest. Sleep is an opportunity to recharge our exhausted brains.
Obviously, when we wake up several times during the night, our brain doesn't have the ability to progress through the various stages of sleep to get the rest it needs. Therefore, upon awakening we can feel exhausted, even if we have "slept" the canonical 8 hours.
In fact, these researchers found that people who woke up several times during the night showed shorter periods of slow-wave sleep, which is the most restful and the time when our brains disconnect from the body.
Of course, this fragmentation of sleep will have repercussions on our mood. Researchers noted that people who could not rest well not only felt more mentally tired, but also reacted with increased irritability as well as decreased sympathy and kindness towards others.
What Happens in the Brain When You Are Not Sleeping?
When we don't sleep well, the activity of the amygdala increases, which plays a key role in triggering negative emotions such as anger and aggression. At the same time, there is a "disconnection" of the amygdala from cortical areas, such as the anterior cingulate cortex, which are what allow us to regulate emotional responses.
In fact, another very interesting study conducted at Tel Aviv University provides new clues as to what happens in the brain when we are not sleeping. These researchers recruited a group of people and asked them to spend a whole night without sleep. The next day they subjected them to an attention test in which images with neutral, positive or negative emotional content appeared.
It was interesting to see that people who had not slept focused more on negative images and displayed unusually high activity of the amygdala, which was activated even with neutral stimuli. This means that when we are not sleeping we lose the ability to be objective and react to stimuli as if they are a threat, even when they are not.
This is why after a sleepless night we are so irritable and angry, and it is very difficult for us to control our reactions.