How Sleep and Stress Are Intertwined

Erik Lundquist, MD -

We've all been there, a night where you cannot fall asleep — the stress of a presentation or life events endlessly looping through your mind, keeping you awake. Not only does poor sleep exacerbate stress, but it also affects our physiological health and quality of life. From academic performance to recovering from (or preventing) COVID-19, sleep is essential for a healthy, happy life.

How Sleep and Stress Are Intertwined

The Anatomy and Physiology of Sleep

There are two types of sleep humans alternate between during the sleep cycle: relaxing, non-rapid eye movement (NREM) and excitatory, rapid eye movement (REM) (1). NREM sleep is associated with gamma-aminobutyric acid (GABA) - a neurotransmitter that inhibits the brain's arousal centers - and hormones like melatonin, corticotropin-releasing hormone (CRH), and growth hormone (GH).

Once the phases of NREM are complete, the body enters REM sleep, which is associated with dreams and excitatory neurotransmitters like acetylcholine and histamine, which stimulates the brain's arousal centers (2). Individuals do not stay in REM but cycle between the two types of sleep throughout the night, toggling between relaxed and excitatory states (2). Approximately 75-80% of sleep is NREM, and 20-25% is REM (1). The average length of the first NREM-REM sleep cycle is 70 to 100 minutes; the cycles that follow are longer, lasting approximately 90 to 120 minutes (1). The body also undergoes physiological changes during both phases of sleep. During REM sleep, blood pressure, heart rate, ventilation, and respiratory flow typically increase compared to their NREM levels (1, 3).

What controls the sleep-wake cycle

Circadian rhythms are the daily physiological and behavioral patterns that control the sleep-wake cycle (1). The rhythms also regulate physical activity, food consumption, body temperature, heart rate, muscle tone, and hormone secretion and are generated by neural structures that function as a biological clock (1). Melatonin is a hormone that helps regulate the circadian rhythm and helps to keep it in sync. Cortisol, a hormone typically associated with stress, has an inverse relationship to melatonin, meaning it's at its peak in the morning so the body can wake up and gradually decreases during the day, while melatonin increases at night. However, when the circadian rhythm is out of sync, so too are the hormone levels, resulting in sleep disturbances (2).

The Link Between Sleep, Stress, and Ability to Cope

The link between stress and sleep often seems like a vicious cycle, with stress causing poor sleep and poor sleep negatively affecting the body's stress response (2).

An Israel study assessed the sleep of 36 students during low and high-stress periods. The results demonstrated that how an individual emotionally responds to stress has more to do with their sleep quality than the type of stress they are exposed to. In the study, they looked at the students' different coping styles, including problem-focused coping (PFC), emotion-focused coping (EFC), and disengaged coping. In the PFC style, students tried to manage or alter the problem causing the stress. In contrast, emotion-focused coping involved regulating emotions in response to the problem, and disengaged coping saw individuals dissociate from the stressful stimuli as well as the related thoughts and feelings (4). The results found that a high EFC score (meaning that they had a highly emotional response to stress) was associated with less sleep and poor sleep quality, while low EFC (meaning that they had a more tempered emotional response to stress) scores were associated with longer, improved-quality sleep (4). Additionally, PFC was associated with more hours of sleep regardless of stress levels (4).

Worry about poor performance leads to sleep disturbances

It's no surprise that stress affects sleep quality. A study that looked at how stress affects the sleep of medical students found that those not suffering from stress are less likely to have poor sleep, while students with a cumulative grade point average of less than 4.25 were almost four times more likely to experience poor sleep (5). Another study found that medical students who perform worse on their medical exams are more stressed and suffer from poor sleep; this poor sleep, in turn, negatively affects their test performance "creating a vicious circle" (6). Recommendations include medical schools establishing academic counseling centers that promote good sleep hygiene and strengthen students' study skills and stress management (5).

Night-shift workers are at increased risk