Have you ever had a sleepless night and the next day felt like your brain was working in slow motion? It’s not just a feeling: sleep deprivation has a profound impact on the brain, and it’s not exactly for the better.
Sleep is not a luxury, it is a biological necessity. The average adult needs between seven and eight hours of sleep each night. However, in a world full of distractions, responsibilities and leisure options, we often sacrifice hours of sleep without thinking about the consequences. What you may not know is what happens in the brain when you don’t get enough sleep.
Getting into sleep debt is not a good idea
It only takes one sleepless night to disrupt your sleep. When you sleep, you go through a cycle of two phases: non-REM sleep (which takes up about 75% of sleep) and REM sleep (which accounts for about 25% of sleep).
During the later stages of non-REM sleep, you get restorative sleep. It’s the most important sleep for recovering and feeling better the next morning. During REM sleep, on the other hand, your brain and body are energized. You’re also more likely to dream and store memories, which take away some of their emotional impact.
REM sleep is therefore important for learning new skills or remembering where you left your house keys the night before. However, when you don’t get enough sleep, all of these stages are shortened or interrupted, which directly affects your ability to process information and manage emotions.
What happens in your brain when you don’t sleep is that you skip those two critical stages of sleep, so you’ll run up what’s known as “sleep debt.” As a result, you’ll experience fatigue, lack of mental alertness, irritability, and persistent daytime sleepiness. If that debt continues to grow, it can open the door to more serious health problems, such as depression or stroke.
What happens to the brain when you don’t sleep and why is it so harmful?
A study by researchers at the University of Edinburgh has found that sleep deprivation reduces the number of different types of synapses – the connections between neurons that allow the transmission of information – in the brain areas associated with learning and memory: the cortex and hippocampus.
Basically, it decreases the number of synapses that recycle proteins quickly, while increasing the number that recycle proteins slowly. This reduces the adaptive capacity of the sleep-deprived brain, potentially affecting learning and synaptic repair.
In fact, previous studies had found that during sleep the brain does not actually switch off completely to rest, but that some areas remain active to eliminate waste substances from the daytime metabolism; in other words, to cleanse the brain internally to eliminate toxins and repair itself. This process, which occurs through the glymphatic system, is crucial to maintaining brain health in the long term.
If you don’t get enough sleep, your brain won’t be able to “clean up,” so those toxins will build up. That could explain the link between insomnia and cognitive decline, which can lead to diseases like dementia.
Furthermore, lack of sleep not only affects your cognitive ability, but also your emotional balance. Sleep affects your mood as the amygdala, the region of the brain responsible for processing emotions, becomes overactive. This can cause you to overreact to stressful situations or feel more irritable and anxious.
At the same time, the prefrontal cortex, which regulates emotional control and decision-making, is affected, making it difficult to stay calm and think clearly. As if that were not enough, when you do not sleep, the production of neurotransmitters such as serotonin and dopamine is also altered, which directly affects mood and motivation.
So, the next time you think about sacrificing hours of sleep to finish watching a series, work late, or simply “beat the clock,” remember that your brain is paying a much higher price than you imagine. It’s not just about feeling tired the next day, but that too little sleep slowly destroys the brain. Ensuring that you get a good night’s restful sleep is an act of love, care, and responsibility towards yourself.
References:
Koukaroudi, D. et. Al. (2024) Sleep maintains excitatory synapse diversity in the cortex and hippocampus. Current Biology; 34(16): 3836-3843.
Zhang, X. et. Al. (2024) The association between insomnia and cognitive decline: A scoping review. Sleep Medicine; 124: 540-550.
Chen, N. et. Al. (2020) Association between Non-Restorative Sleep and Quality of Life in Chinese Adolescents. Int. J. Environ. Res. Public Health; 17(19): 7249.
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