Lack of sleep, most people will go insane?
2023-12-02
When I was a graduate student, I worked with colleagues to study how a night without sleep affects a person's ability to manage emotions. At the time, we were running weekly trials, and I would often stay up late on Friday nights to monitor participants and make sure they were following the protocol. By noon the next day, we all stumbled out of the lab, exhausted and just wanting to go home and sleep.
Two months into the experiment, one day, while I was sitting in the car waiting for a traffic light, a love song was playing on the radio station. Suddenly, I cried uncontrollably. At that moment, I was surprised at my own reaction, and then it suddenly dawned on me that I was not only studying the effects of sleep deprivation, but also being part of it. Weeks of sleep deprivation had taken a toll on me and I was no longer able to control my emotions properly.
This study and many that have followed have demonstrated a strong and close link between better sleep and emotional health. In healthy people, high-quality sleep is associated with more positive moods, but just one night's sleep loss can make people feel more anxious and depressed the next morning. Additionally, people with chronic sleep disruption tend to be more negative in their daily lives and find it difficult to shake off a pessimistic mindset. In fact, in a national sleep survey, 85% of Americans said their mood suffers when they don't get enough sleep.
We and other researchers are beginning to uncover how sleep deprivation damages the inner structure of our brains. One of the many effects of sleep deprivation is disruption of neural circuits in the brain that regulate mood
For decades, researchers and medical professionals believed sleep deprivation was a byproduct of depression or anxiety. In other words, people feel anxious first and then become sleep-deprived. Now we know that this order can be reversed. In fact, sleep deprivation and anxiety, depression, or other mental health conditions can interact to create a vicious cycle that is extremely difficult to break.
Many studies of chronic insomnia or insomnia provide evidence of this. Compared with people who sleep well, people with insomnia are twice as likely to develop depression or anxiety later in life. For example, one study that followed 1,500 people, some of whom had insomnia and some of whom did not, found that chronic insomnia was associated with a three-fold increase in depression and a two-fold increase in anxiety attacks one year later.
Insomnia symptoms increase the risk of post-traumatic stress disorder. Additionally, people with sleep disorders are at greater risk for recurrence of these disorders than people whose sleep improves, despite receiving adequate antidepressant or anxiety treatment. Understanding the role of sleep in these disorders could provide new insights to help prevent and treat many mood and mental disorders.
Earlier studies have found that sleep deprivation may be a precursor to serious mental health symptoms in healthy people. These studies were mainly conducted in the 1960s. After being asked to stay awake for more than two nights, participants reported having trouble thinking, forming words, and constructing sentences. They begin to experience hallucinations, such as seeing inanimate objects moving, or feeling someone touching them when they are alone. After going without sleep for three days, some people begin to have delusions and become paranoid. They feel like they are secret agents, or that aliens are out to get them (which sounds like a psychotic episode, because it is). After five days, some participants entered a state similar to clinical psychosis and were no longer able to fully understand their situation.
In one study, some participating U.S. soldiers tried to stay awake for more than four nights. One of the soldiers, who was considered quiet and reserved by his friends, became very aggressive after staying awake for three consecutive nights. He would initiate fights and insist that he was on a secret mission for the president. Eventually, he was forcibly subdued and expelled from the experiment. In addition, 6 people showed violent tendencies and persistent hallucinations. However, after a full day's sleep, the soldiers returned to normal and had no memory of their previous confusing behavior. Given the devastating effects of chronic sleep deprivation, it is now considered unethical to conduct such studies, but these results are still persuasive and remind us that our mental and psychological well-being is highly dependent on sleep.
Even with these alarming consequences, scientists remain skeptical about the consequences of insomnia, especially considering the tiny minority of people who can tolerate extreme sleep deprivation. This is also the focus of the latest wave of sleep research. In recent years, scientists have begun to elucidate from a neuroscientific perspective that lack of sleep may be directly linked to changes in our moods.
Whenever we are frightened or nervous, a region deep in the brain called the amygdala activates. The amygdala triggers a comprehensive response throughout the body in response to a challenge or threat. This flight or fight response increases our heart rate and stress hormones flood our bloodstream. Fortunately, there is another brain region standing between us and this cascade of excessive stress responses: the prefrontal cortex, an area located behind the middle of the eyebrows. Research shows that activity in this brain region suppresses or downregulates activity in the amygdala, which keeps our emotions in check.
In studies that my colleagues and I conducted, we performed functional magnetic resonance imaging (fMRI) on healthy volunteers after a night of sleep deprivation and found a dramatic decrease in activity in their prefrontal cortex. Furthermore, neural activity connecting the amygdala to the prefrontal cortex was significantly weaker. In other words, when sleep is affected, the brain areas and neural circuits that control emotional responses basically enter a state of chaos. Other studies have found that this disturbance in neural activity can appear after people have been up all night and after chronically sleeping less than six hours - this was also seen if participants slept only four hours a night for five days.
Lack of sleep can have a severe impact on people's emotion perception and control, making it difficult for people to distinguish what emotions are. For example, when my colleagues and I had participants view neutral and emotional photos (such as those of expressionless commuters on a train and a crying child), fMRI showed that their amygdala Checking out these photos had mixed reactions. But after being up all night, people's amygdala responded strongly to both types of photos.
In other words, when the amygdala fails to function in conjunction with the prefrontal cortex, the brain's threshold for emotionality is significantly lowered. Impaired emotional control can make us more susceptible to anxiety and negative emotions, and listening to love songs can make us want to cry.
The effects of sleep loss on the amygdala, prefrontal cortex, and neural circuits between the two may also have many other consequences. Research we published in January this year showed that changes in this neural circuit and other brain areas related to wakefulness are also associated with increased blood pressure after a night of sleep deprivation. My colleagues and I have observed mechanistic changes at the brain level that may have adverse effects throughout the body, including increased risk of hypertension and cardiovascular disease.
Taking a step back, it becomes clear that mental and emotional health, like our physical health, relies on a delicate balance. The countless choices we make every day and night are all about maintaining this balance. Therefore, even a trivial sleepless night can tip the balance. We need to remember this fact, for our own sake and for the sake of those who care about us. Inevitably, we all miss sleep from time to time. However, our society should take a critical look at the factors that prevent people from getting enough rest, such as inappropriate work practices and campus culture - which can prevent people from getting enough rest. Scientific research on sleep and mental health shows that if these issues are not addressed, people will be vulnerable to serious harm.
