Why the human mind is not meant to be awake after midnight

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  • Past studies show that being awake late at night is unhealthy for physical and mental health.
  • New research suggests that there might be a biological basis for certain behaviours at night.
  • The authors of the current study are calling for more research into this, as late nights can be dangerous.

If you’re like me, you may feel like your most productive hours are when most people hit the hay. Or you might be guilty of ‘revenge bedtime procrastination’ - deliberately putting off sleep so that you can fit in leisure time after a busy day. 

Then there's the Covid-19 pandemic that has led many of us to transition to work from home. For many professionals, this has meant longer hours in front of their desks - especially late into the night.

But here’s the problem: scientists say our brains are not meant to be awake after midnight. Past research indicates that our minds focus differently at night, when awake, than in the day - and not in a good way. 

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Research suggests that night-shift workers may be more likely to have depression than those working daytime schedules. This is because they do not work and sleep in line with their circadian rhythm -- our natural 24-hour internal clock in your brain that regulates our daily schedule for sleep and alertness. As a result, their biological and social time are misaligned.

In a new study looking at the evidence of how the human brain systems function differently after dark, researchers propose a hypothesis called 'Mind After Midnight'. They suggest that our body and mind follow this 24-hour cycle of activity that influences our emotions and behaviour.

Simply put: our brain is designed to behave in certain ways at certain hours of the day. At night, we are meant to be asleep. Research also shows that ‘positive affect’, the tendency to view information in a positive light, peaks during the morning, when our circadian influences are tuned to wakefulness and are at their lowest during the night. 

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By contrast, the tendency to view information in a negative light is highest at night. So if you ever find yourself going down a rabbit hole of negative thoughts just before bedtime - you’re not alone. 

Co-author of the study, neurologist Elizabeth Klerman from Harvard University, said in a news release:

"There are millions of people who are awake in the middle of the night, and there's fairly good evidence that their brain is not functioning as well as it does during the day.”

Heroin user: resistance in the day vs night

In their paper, published in the journal Frontiers in Network Physiology, the team’s hypothesis draws on four behaviours to illustrate their point: suicide/self-harm, violent crime, alcohol or other substance use, and food intake.

They go on to give two examples: the first is of a previously abstinent heroin user who successfully manages cravings during the day, but may experience greater cravings and lesser resistance at night. 

“... a dose that was sufficiently rewarding during the day may be insufficient at night, potentially resulting in an increased dose, repeated use, or both, as the risk of overdose is downplayed or discarded. If this process repeats night after night, a conditioned pattern of nighttime heroin use may emerge,” they write.

The second example

The second example is of a college student experiencing “nocturnal wakefulness” due to a delayed sleep schedule and insomnia. The student begins to feel isolated and alone, which leads to endless rumination on their past negative relationship experiences. This builds, and they eventually feel a sense of hopelessness and despair.

They write: 

Suicide, previously inconceivable, emerges as an escape from loneliness and pain, and before the costs of suicide are considered the student has acquired the means and is prepared to act at a time when no one is awake to stop them.

These examples, they go on to say, demonstrate how impaired judgement and impulsivity while awake at night (nocturnal wakefulness) may increase the incidence and appeal of dangerous ideas, and could prove fatal.

A previous study concluded that nocturnal wakefulness is a suicide risk factor, "possibly through misalignment of circadian rhythms."

Sleep debt, the cumulative effect of not getting enough sleep, could explain these behaviours. But it is also possible that nighttime neurological changes play a key role. Yet, worryingly, research on this is lacking, considering millions of people globally are working night shifts.

Says Klerman: 

My plea is for more research to look at that, because their health and safety, as well as that of others, is affected.

Interestingly, a study this year found that doctors working night shifts had less empathy in managing patients than those working day shifts due to sleep deprivation, fatigue and stress. They were, therefore, less likely to prescribe painkillers, even when patients needed them.

“Even medical experts who strive to provide the best care for their patients are susceptible to the effects of a night shift,” wrote the study’s researchers. Importantly, while their study focused on doctors, their results should matter to all people who are sleep-deprived, they said.  

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