The sleep-stress connection
Who hasn’t experienced a restless night full of tossing and turning from worry about a test, interview or presentation the next day? Stress and worry affect your quality of sleep which, in turn, affects your ability to handle stress. Difficulties with sleep or stress management can produce a vicious circle of decreased sleep and increased stress.
Although the sleep-stress link is complex, and researchers are unclear on the exact physiology behind it, we do have some clues. The hypothalamic-pituitary-adrenal (HPA) axis is the primary regulator of the stress response. The hypothalamus, a part of the brain, directs the pituitary, another gland in the brain, to signal the adrenal glands, located above the kidneys. In response to this signal the adrenal glands secrete stress hormones, like adrenaline and cortisol, that have widespread effects throughout the body: raising blood pressure, elevating blood sugar, increasing heart rate, and even causing anxiety.
The level of cortisol the body produces has a normal daily rhythm that somewhat parallels the normal sleep-wake cycle. Cortisol peaks in the early morning, declines throughout the day, and reaches a low around midnight. The level starts to rise again during the second half of the night. However, many types of stress (extreme physical activity, worry about a family member’s health, going too long between meals) can trigger the stress response and disrupt this normal cycle.
Excessive stress can cause healthy adrenal glands to increase cortisol output throughout the day and into the evening, putting a burden on the body from all the metabolic changes induced by the hormone. On the other hand, in people with adrenal fatigue, cortisol levels typically can’t reach their normal morning high or rise in response to demand, making it more difficult to handle any stress.
Effects of lack of sleep
Prolonged insomnia is associated with elevated nighttime cortisol levels and lower morning cortisol levels. People who chronically sleep less than 9 hours a night tend to have higher cortisol levels throughout the time that they sleep and are at higher risk for obesity and diabetes than people who sleep for more than 9 hours.
The evidence for the relationship between short-term lack of sleep and cortisol is a bit more contradictory. After a period of sleep loss, some studies show elevation of cortisol, while others report a decrease in cortisol. Some researchers theorize that, initially, the stress response system is stimulated in order to cope with and adapt to sleep loss, but over time the continued lack of sleep causes a blunting of the response. This could also be due to an inability of the adrenal glands to continue to respond to the stressor.
One of the primary functions of sleep is to consolidate new memories. Much of this process involving memories about facts and information happens during slow wave sleep, which occurs in the early night. When low dose cortisol was given to people during this sleep phase (similar to what could occur in the body under stress), their memory was impaired.
Although we’re not clear on which may be the proverbial chicken or egg, sleep disturbances and cortisol imbalances are both common in insomnia, depression, sleep apnea, restless leg syndrome, menopause, Cushing’s syndrome (a syndrome in which cortisol is significantly high) and adrenal fatigue (in which cortisol is significantly low).
About the author
Dr. Lise Naugle is an associate of Dr. James L. Wilson. She assists healthcare professionals with clinical assessment and treatment protocols related to adrenal dysfunction and stress, and questions regarding the use of Doctor Wilson’s Original Formulations supplements. With eleven years in private practice and a focus on stress, adrenals, hormonal balance and mind-body connection, she offers both clinical astuteness and a wealth of practical knowledge. Dr. Naugle also maintains updated information about the latest scientific research on the hypothalamic-pituitary-adrenal axis function, endocrine balance and nutritional support for stress and develops educational materials about stress and health for clinicians and their patients.