Why You Wake Up at 2am
Professor Michelle Spear, Professor of Anatomy at the University of Bristol, has explained why many people find themselves awake at 2am and how to overcome it. According to Spear, being alert in the middle of the night is a hard-wired survival instinct, but it can be changed.
"The brain does not simply fall asleep because the body is fatigued. In fact, under stress, exhaustion and sleeplessness often occur together. Part of the reason lies in the biology of survival. The human stress response evolved to deal with immediate physical threats," Spear said.
"For most of human history, danger tended to be extreme and short-lived – a predator nearby, an environmental hazard or conflict with another human group. In those moments, the brain’s priority was not rest but survival. When the brain detects threat, a region called the amygdala initiates the body’s classic fight-or-flight response."
Modern Stress Keeps the Brain Alert
Stress hormones including adrenaline and cortisol are released, increasing heart rate, breathing, and attention. Energy is diverted from long-term maintenance to immediate action. While useful for escaping a predator, this response is less helpful for modern threats like an overflowing inbox or financial pressure.
Professor Spear noted that modern threats "rarely resolve quickly." She explained: "Emails continue arriving. Work follows us home through smartphones and laptops. Social media creates a constant stream of social comparison and low-level vigilance. Even leisure time has become strangely porous, interrupted by notifications, messages and often the expectation of permanent availability."
The result is that the brain's alertness centers remain "partially activated" for long periods.
The Science of Hyperarousal
"Sleep is not simply the absence of wakefulness. Falling asleep requires the brain to actively reduce alertness. A network of arousal centres in the brainstem, hypothalamus and forebrain normally keeps us awake and attentive during the day. To transition into sleep, these systems must quieten down," Spear told The Conversation.
"Under long-term stress, however, the brain can become stuck in a state of hyperarousal. Even when the body is exhausted, the brain continues scanning, anticipating and rehearsing. From an evolutionary perspective, this makes a certain kind of sense. If the environment feels threatening or uncertain, being fully offline may not seem safe."
Tired Body, Racing Mind
Physical exhaustion and mental arousal are controlled by overlapping but partly separate systems. "Your muscles may desperately need rest while your brain continues producing stress-driven alertness. The result is the strange mismatch many people know well, a tired body and racing thoughts," Spear said.
Under normal circumstances, cortisol follows a daily rhythm, rising in the morning and declining towards night. Chronic stress can disrupt this pattern, leaving the body activated later into the evening.
Other Factors: Light and Screens
Artificial light suppresses melatonin, the hormone that regulates sleep timing. Smartphones provide endless cognitive stimulation when the brain should be winding down. "Doomscrolling combines emotional arousal, uncertainty and novelty – three things human attention systems find almost impossible to ignore," Spear explained.
What Actually Helps
"Sleep researchers often emphasise that rest and safety are closely linked in the brain. Consistent routines, reduced evening stimulation, exercise, daylight exposure and limiting late-night screen use can all help reinforce the signals that night is a time for recovery rather than alertness. Cognitive behavioural therapy for insomnia has also proved remarkably effective, partly because it targets the cycle of anxiety and sleeplessness itself," Spear said.
"Perhaps the most important point is broader. Feeling 'wired but tired' is not evidence that your body has failed to rest properly. Often it is evidence that the brain has become too good at staying alert in a digital world that never really stops."
