The One Thing Your Brain Needs to Truly Sleep at Night

Millions of Americans struggle to get a good night's sleep, but according to a cognitive neuroscientist who recently spoke with Newsweek, the problem may run deeper than a poor bedtime routine.

The brain's ability to sleep is closely tied to whether it feels safe enough to switch off, with unresolved stress and anxiety potentially keeping people trapped in a state of heightened alertness.

Cognitive neuroscientist Yousuf Aslam told Newsweek that sleep regulation involves a "complex interplay" between neuroscience, psychology, neurochemicals, and physiological processes. While biological mechanisms help regulate sleep, he said emotional factors can be just as important.

How the Brain Regulates Sleep

Aslam, who has a focus on neuromechanics and a strong academic background in neuroscience and biochemistry from Queen Mary University, London, explained that two primary biological systems regulate sleep: the circadian rhythm and sleep-wake homeostasis.

"The circadian rhythm, our internal 24-hour clock, is governed by the suprachiasmatic nucleus in the hypothalamus," he said, noting that it adjusts melatonin production in response to light and darkness.

The second system, sleep-wake homeostasis, tracks how much sleep the body needs. Aslam said it is regulated by adenosine, a chemical that builds up during waking hours and declines during sleep. Caffeine promotes alertness because it blocks adenosine receptors.

However, he said sleep involves more than biology alone.

"Beyond these, stress and emotion regulation significantly impact sleep," Aslam said, noting that stress can increase cortisol production and interfere with normal sleep processes.

When the Brain Feels ‘Unsafe’

According to Aslam, there are two key stress-related causes of sleep disruption.

The first stems from unresolved experiences or perceived shortcomings from the past. He said the brain can become agitated because it "feels unsafe due to past memories," whether from painful events, unresolved issues or a persistent feeling that “I haven’t achieved or done enough.”

The second is anxiety about the future. Aslam described this as the brain feeling unsafe about "future memories"—anticipating negative outcomes, dreading upcoming responsibilities or worrying that there is simply too much ahead to do.

In both cases, he said the brain struggles to relax. "When the brain feels 'unsafe,' it officially enters something called the sympathetic nervous response, also referred to as the flight or fight response," Aslam said. Elevated heart rate and increased brain activity make it harder to fall asleep and remain asleep.

For sleep to occur, the brain must first slow down, Aslam said, and in order to do this, “it needs to feel safe,” and secure enough to reduce the volume of thoughts and transition away from a state of stress.

He compared the process to moving from overthinking to a state of cognitive and physical relaxation. Brain activity must shift from beta waves, which are associated with wakefulness and stress, to alpha waves, "the gateway to cognitive relaxation," before deeper sleep stages can occur.

People who cannot make that transition often resort to scrolling on their phones late into the night. Aslam said his team frequently finds that such individuals spend hours on mobile devices, subconsciously trying to exhaust themselves before eventually falling asleep from fatigue.

A Nightly Exercise for Better Sleep

To address these underlying stressors, Aslam recommends a nightly gratitude-writing exercise.

The practice involves writing down three things you are grateful for from the day or anything from your past, three things you are grateful for about tomorrow, and four things you appreciate about yourself in the present.

"Essentially, we are training the brain to feel secure about what's happened, what will happen, and how things are in the present moment," he said.

Aslam recommends completing the exercise immediately before bed because the brain continues processing thoughts for up to four hours after sleep begins.

“Often, people go to sleep thinking about the day they’ve had or the day ahead. The brain keeps working on this trying to ‘solve’ these concerns—and you wake up exhausted, even though you may have slept for seven to eight hours,” Aslam explained. “It is not necessarily the quantity of sleep that is key, it is the quality of sleep.”

Rather than focusing on worries, the goal is to fall asleep with feelings of security and gratitude.

Aslam also advises writing the gratitude list by hand using a pen and capital letters rather than a phone or digital device, “because the brain perceives paper and ink differently to digital devices.”

In the morning, he recommends reading the list within 45 minutes of waking up, “as the brain is more susceptible to reprogramming.”

He said to read this list instead of immediately checking messages or emails, which he said can trigger a cortisol-driven stress response.

“The same reason why you should delay your first cup of caffeinated drink to after 45 minutes of waking, to reduce the cortisol spike,” he noted.

Aslam said improving your sleep can impact your "mental health as a whole, including improved focus, clarity, and memory abilities.”

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Contact Newsweek editors for this story: Kara Dolman and Anthony Murray.