In the middle of the night, the world can sometimes feel like a dark place. Under cover of darkness, negative thoughts have a way of drifting through your mind, and as you lie awake staring at the ceiling, you might start craving guilty pleasures, like a cigarette or a high-carb meal. .
There is plenty of evidence to suggest that the human mind works differently if it’s awake at night. After midnight, negative emotions tend to grab our attention more than positive ones, dangerous ideas gain traction, and inhibitions fall away.
Some researchers believe that the human circadian rhythm is strongly involved in these critical changes in function, as they point out in a new paper summarizing the evidence for how brain systems function differently after dark.
Their hypothesis, called “Mind After Midnight”, suggests that the human body and human mind follow a natural 24-hour cycle of activity that influences our emotions and behavior.
In short, at certain times our species is prone to feel and act in certain ways. During the day, for example, molecular levels and brain activity are adapted to the waking state. But at night, our usual behavior is to sleep.
From an evolutionary perspective, this of course makes sense. Humans are much more efficient at hunting and gathering in daylight, and although nighttime is ideal for resting, humans were once more at risk of being hunted.
According to the researchers, to cope with this increased risk, our attention to negative stimuli is exceptionally heightened at night. Where it might once have helped us jump on unseen threats, this hyper-focus on the negative can then fuel an altered reward/motivation system, making a person particularly prone to risky behaviors.
Add sleep loss to the equation, and this state of consciousness only becomes more problematic.
“There are millions of people who are awake in the middle of the night, and there’s pretty strong evidence that their brains aren’t functioning as well as they did during the day,” says neurologist Elizabeth Klerman of Harvard University.
“My plea is for more research to look at this because their health and safety and that of others is affected.”
The authors of the new hypothesis use two examples to illustrate their point. The first example is of a heroin user who successfully manages his cravings during the day but succumbs to his cravings at night.
The second is of a college student struggling with insomnia, who begins to feel a sense of hopelessness, loneliness, and hopelessness as the sleepless nights pile up.
Both scenarios can ultimately prove fatal. Suicide and self-harm are very common at night. In fact, some research reports a three times higher risk of suicide between midnight and 6 a.m. compared to any other time of day.
A 2020 study concluded that nighttime awakening is a risk factor for suicide, “possibly through a misalignment of circadian rhythms.”
“Suicide, previously inconceivable, appears as an escape from loneliness and pain, and before the costs of suicide are considered, the student has acquired the means and is ready to act at a time when no one else ‘is awake to stop them’, the authors of the ‘Mind After Midnight’ hypothesis explains.
Illegal or dangerous substances are also consumed more at night. In 2020, research conducted at a supervised drug consumption center in Brazil found a 4.7 times higher risk of opioid overdose at night.
Some of these behaviors could be explained by sleep debt or the cover provided by darkness, but there are likely also nocturnal neurological changes at play.
Researchers like Klerman and his colleagues believe we need to dig deeper into these factors to make sure we’re protecting those most at risk from nighttime awakenings.
To date, the authors say that no studies have examined the impact of sleep deprivation and circadian rhythm on a person’s reward processing.
As such, we don’t really know how shift workers, such as pilots or doctors, cope with their unusual sleep routine.
For about six hours a day, we know surprisingly little about how the human brain works. Whether asleep or awake, the mind after midnight is a mystery.
The study was published in Frontiers in Network Psychology.