What is the Purpose of Sleep?

What is the Purpose of Sleep?

Every night, human beings do something amazing. We lie down in bed, and our brains and bodies spontaneously undergo a transition into sleep. We become temporarily paralyzed (to a degree), and experience states of dreaming and unconsciousness. As we dream, we explore vivid yet unreal worlds within our own minds, and often have no idea we are dreaming at all.

Of course, human beings are not the only ones who sleep. Most other animals sleep as well, and sleep has even been observed in insects.

One would think something as basic and prevalent as sleep would be a phenomenon that we understand well. But it isn’t.

In fact, scientists are unclear as to the purposes of sleep. Research does suggest sleep likely fulfils more than one, however.

What Does Science Tell Us About Why We Sleep?

Sleep is essential for restorative processes in our bodies. Instinctually, you probably are aware of that. Think how many times you have gone to sleep with sickness or injury, and woken up feeling a little bit better.

 Harvard explains, “Sleep provides an opportunity for the body to repair and rejuvenate itself. In recent years, these ideas have gained support from empirical evidence collected in human and animal studies. The most striking of these is that animals deprived entirely of sleep lose all immune function and die in just a matter of weeks.”

It also appears that sleep is important for brain plasticity and learning.

The BBC writes, “During the day brain cells build connections with other parts of the brain as a result of new experiences. During sleep it seems that important connections are strengthened and unimportant ones are pruned. Experiments with sleep-deprived rats have shown that this process of strengthening and pruning happens mostly while they sleep.”

While this is happening, our brains also are clearing out a by-product of cell activity called adenosine.

Harvard says, “A link between sleep and brain plasticity is becoming clear in adults as well [as children]. This is seen in the effect that sleep and sleep deprivation have on people's ability to learn and perform a variety of tasks.”

What is the Purpose of Dreaming?

Dreaming in particular seems tied to brain flexibility, as explained in this article in Time. That suggests a role in learning and task performance, as mentioned above. But the Time article discusses another intriguing theory.

The Time article explains that due to the rotation of the Earth, we experience cycles of darkness every night. The brain, it turns out, is so flexible that it only takes brief exposure to a lack of visual stimuli for the visual cortex to start transferring functionality to other senses as an adaptation.

One reason we may have visual dreams is so that our visual cortex’s functionality does not get redistributed due to having to experience darkness each night. But even nocturnal species need to dream, given that they still sleep, albeit during daytime. Since their eyes are closed during that time, their brains still need to protect the visual cortex’s function. This theory is referred to as the “defensive activation theory.”

The post concludes, “Although dreams have long been the subject of song and story, they may be better understood as the strange lovechild of brain plasticity and the rotation of the planet.”

Dreaming During Life’s Challenging Times

Coming back to the connection between dreaming and learning, have you ever noticed that your dreams seem more vivid or memorable when you are especially stressed?

If so, you are not alone. Researchers have noticed a link here too. As explained here, “During times of stress and anxiety we either dream more or remember our dreams more often, as a way of coping with challenging circumstances and new information.” This post continues, “This is also in line with another theory of dreaming – the mood regulatory function of dreams theory, where the function of dreams is to problem-solve emotional issues.”

The article adds, “While there is no evidence that we dream more when we are stressed, research shows we are more likely to remember our dreams because our sleep is poorer and we tend to wake in the night more frequently.”

The post goes on to cite a fascinating study on people who had gone through a divorce. The researchers discovered that participants were more likely to recover from divorce-related depression after a year if they dreamed about their ex. This suggests that dreaming about specific life problems may help us process our emotions and get back to equilibrium.

Are You Getting Enough Sleep?


Now you understand at least a few of the reasons why sleep and dreaming are so important. But the reality is that sleep deprivation is widespread. According to the CDC, around a third of Americans are not getting enough sleep.

If you are having a hard time getting a sufficient amount of sleep, you may need to make some changes in your routine.

For starters, you should try and have a schedule for sleep that is the same each day. Wake up at the same time if you can, and go to bed at the same time if possible.

For another thing, you may want to work on improving your sleep hygiene. “Sleep hygiene” refers to having an environment and healthy habits that support restorative sleep. One simple example is having a supportive mattress and pillow. Another is avoiding eating spicy foods or large meals late at night.

A healthy diet and exercise may also help you sleep. So might addressing any underlying psychological difficulties (i.e. stress, anxiety or depression).

Once you start getting the right amount of nightly rest, you should start waking up feeling more refreshed in the mornings. Your body and brain will have more of what they need to function at their best. You will also be supporting your long-term health.


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