Cortisol and Sleep: How the Stress Hormone Affects Night-time Rest

Figure 1: A balanced cortisol rhythm is an important prerequisite for restorative sleep and an intact internal biological clock.

Sleep problems are among the most common health complaints of our time. Many people feel exhausted in the evening but have difficulty falling asleep or wake repeatedly during the night. One possible cause is a disrupted cortisol rhythm. Cortisol, also known as the “stress hormone”, plays a central role in our sleep–wake cycle. In this blog post you will learn what functions cortisol performs in the body, how elevated cortisol levels can impair sleep quality, and which naturopathic and practical everyday measures can help support a healthy cortisol rhythm.

What is cortisol?

Figure 2: Cortisol is produced in the adrenal cortex and fulfils a variety of vital functions in the energy, metabolic and immune systems.

The hormone commonly referred to as the “stress hormone”, cortisol, is produced in the adrenal cortex and belongs to the group of glucocorticoids. Its secretion increases particularly in situations of physical or psychological stress. However, cortisol is not only produced during stress; it carries out numerous essential functions in the human organism around the clock. Release is controlled via the hypothalamic–pituitary–adrenal axis (HPA axis) — a complex hormonal regulatory system that precisely adjusts cortisol production to the body’s current needs.

One of cortisol’s most important functions is the provision of energy. Among other things, the hormone ensures that sufficient glucose is available to the body in stressful situations. It promotes the production of new glucose in the liver and also affects the metabolism of carbohydrates, fats and proteins. In addition, cortisol contributes to the maintenance of normal blood pressure and the normal functioning of the cardiovascular system. At the same time, it regulates numerous immunological processes and has anti-inflammatory effects — a property that is also used therapeutically, for example in the treatment of inflammatory or allergic diseases with corticosteroid preparations.

Because the hormone is vital for life, the aim should not be to lower cortisol as much as possible or to avoid it completely. Rather, it is about the right amount at the right time. A balanced cortisol level helps the body to be alert and responsive in the morning and to react appropriately to stressors. Cortisol only becomes problematic when the natural daily rhythm is chronically disturbed. The next section explains the negative effects that elevated cortisol can have on sleep quality.

The natural cortisol rhythm and its importance for sleep

Figure 3: An intact cortisol rhythm is characterised by high values in the morning and low concentrations in the evening.

Our internal biological clock — the circadian rhythm — is of enormous importance for restorative sleep. Cortisol and the sleep hormone melatonin play key roles in this finely tuned system. Cortisol reaches its peak in the morning and prepares the body for waking, then declines steadily during the day. In the evening and during the first half of the night, cortisol levels should ideally be particularly low so that the organism can relax and melatonin can exert its sleep-promoting effect. A few hours before waking, cortisol begins to rise again to prepare the body for the new day.

If this natural daily rhythm falls out of balance, sleep quality is often affected directly. Chronic stress, persistent rumination, sleep deprivation, shift work or a generally restless, hectic lifestyle can prevent cortisol from falling sufficiently in the evening. The body then remains in a state of heightened alertness although it should be preparing for night-time rest. Typical consequences are problems falling asleep, frequent nocturnal awakenings, early waking, or feeling unrefreshed in the morning despite adequate sleep duration. In addition, sleep deprivation can increase activity of the hypothalamic–pituitary–adrenal axis (HPA axis) and thereby further raise cortisol secretion. This creates a vicious circle in which stress and sleep problems reinforce each other.

What does the science say about the relationship between cortisol and sleep?

The close interplay between cortisol and sleep is supported by numerous scientific studies. For example, a 2021 review names low evening cortisol levels and a rise in the early morning as essential prerequisites for an intact sleep–wake rhythm.¹ Another review from the same year concludes that elevated evening cortisol levels are often associated with poorer sleep quality and sleep disorders.² Earlier studies also show that chronic stress, sleep deprivation and elevated cortisol levels can mutually reinforce one another and promote various sleep problems in the long term.³

These findings are supported by observational studies. In one study of adults aged 56 to 75, participants with an ideal nocturnal cortisol dynamic rated their own sleep quality significantly better than those with a disturbed cortisol profile.⁴ A 2017 study also found indications that sleep disorders and frequent nocturnal awakenings often coincide with elevated nocturnal cortisol levels.⁵ Although cortisol is only one of many factors that can affect sleep, the current body of evidence nevertheless strikingly highlights how important an intact cortisol rhythm is for restorative night-time sleep.

Supporting the cortisol rhythm naturally: aromatherapy and adaptogens

Figure 4: Aromatherapy and adaptogens can promote a healthy cortisol rhythm and support the body in different ways to cope better with stress.

There are various naturopathic approaches that can help the body cope better with stress and promote a balanced cortisol rhythm. In recent years, aromatherapy and so‑called adaptogens — plant-based substances thought to increase resilience to physical and psychological stress — have been studied particularly intensively. It is important to emphasise, however, that neither approach replaces good sleep hygiene or medical treatment, although they can sensibly complement them.

1. Adaptogens

Adaptogens are medicinal plants believed to support the organism in adapting to stress. They are said to help regulate the activity of the central hormonal stress system — the hypothalamic–pituitary–adrenal axis (HPA axis) — and thus to mitigate the body’s stress response. The best-known adaptogens include Ashwagandha (sleepberry) and roseroot (Rhodiola rosea).

Scientific evidence for these plants has increased significantly in recent years. For example, a recent systematic review evaluated clinical trials on Ashwagandha and roseroot.⁶ The authors found indications that both plants reduce stress, improve psychological well‑being and may — via modulation of the HPA axis — also contribute to better sleep quality. Although further high‑quality studies are needed to confirm this, current results suggest that adaptogens could be supportive, especially for stress-related sleep problems.

2. Aromatherapy

Aromatherapy uses essential oils to positively influence body and mind. Through the sense of smell, the fragrance molecules reach the limbic system — the brain area involved in the regulation of emotions and stress responses. Lavender oil, in particular, is among the most well‑studied essential oils in relation to sleep and relaxation. It can be used, for example, in a diffuser, as a pillow spray, as a bath additive or as a diluted massage oil.

The evidence from studies is overall positive. A recent meta‑analysis of eleven randomised controlled trials involving a total of 628 participants showed that lavender aromatherapy can significantly improve sleep quality in adults.⁷ A similar conclusion was reached by another systematic review that analysed 34 studies: inhalation of lavender oil was particularly associated with shorter time to fall asleep and improved sleep quality.⁸ In a pilot study, inhaling lavender oil during sleep also reduced concentrations of various stress markers such as α-amylase and chromogranin A.⁹ The results indicate that aromatherapy can help the body relax and dampen nocturnal stress responses. However, further high‑quality studies are required to assess long‑term effectiveness conclusively.

From daylight to evening routine: 7 tips for a balanced cortisol balance

Figure 5: Regular sleep times, daylight and appropriate relaxation rituals support the natural sleep–wake rhythm and cortisol regulation.

A balanced cortisol rhythm cannot be achieved through a single measure. Rather, it is the result of various lifestyle factors that complement each other and synchronise the body’s internal clock daily. Small changes in daily life can help support natural cortisol secretion and thereby improve sleep quality in the long term. The following seven recommendations are based on findings from chronobiology and sleep research and can be integrated into everyday life with little effort.

• Start the day with plenty of daylight: Natural daylight in the morning is one of the most important cues for the internal biological clock. Even a 20– to 30‑minute stay outdoors — ideally within the first hour after getting up — can support natural morning cortisol release and help stabilise the circadian rhythm. At the same time, it prepares the body for later melatonin production, which can make it easier to fall asleep in the evening.
• Keep consistent bed and wake times as far as possible: Regular bed and wake times are an important building block for a stable sleep–wake rhythm. Try to go to bed and get up at similar times every day — including at weekends. This supports the natural interplay between cortisol and melatonin. Frequently changing sleep times, on the other hand, can upset the internal clock and negatively affect sleep quality and cortisol regulation in the long term.
• Incorporate physical activity into your daily routine: Regular physical activity is one of the most effective non‑pharmacological measures for reducing stress. Endurance training, strength training or brisk walks can help improve stress regulation and positively influence HPA axis activity in the long term. Even moderate exercise on most days of the week can benefit sleep quality, well‑being and the natural cortisol rhythm.
• Avoid intense training late in the evening: Although physical activity is generally healthy, the timing of exercise can sometimes affect individual sleep quality. Very intense workouts late in the evening can temporarily increase the release of stress hormones and put the body into an activated state. If you are sensitive to late‑night training, try to schedule intense sessions in the morning or afternoon and favour gentler forms of movement such as yoga or a walk in the evening.
• Use caffeine consciously: Caffeine blocks adenosine receptors in the brain and can thus suppress tiredness.¹⁰ In sensitive individuals, it also affects cortisol secretion and can make falling and staying asleep more difficult. Therefore, avoid caffeinated drinks such as coffee, energy drinks or black tea from the afternoon onwards where possible. How strongly caffeine affects sleep varies between individuals.
• Reduce screen time before bedtime: Smartphones, tablets and computers stimulate the brain not only through their content but also through their high proportion of blue light. This can inhibit melatonin production and thereby shift the natural sleep–wake rhythm.¹¹ Turn off digital devices one to two hours before bed where possible, or at least enable a blue‑light filter to make it easier for your body to transition into night‑time rest.
• Establish relaxing evening rituals: Repeating rituals in the evening signal to the body that the active phase of the day is coming to an end. Relaxing activities such as meditation, breathing exercises, progressive muscle relaxation, gentle yoga or reading a book can help reduce activity of the autonomic nervous system and ease the transition to sleep. Evening rituals are most effective when carried out regularly and firmly embedded in the daily routine.

When should you seek medical advice?

A disturbed cortisol rhythm can impair sleep quality, but it is only one of many possible influencing factors. Occasional problems falling or staying asleep are common in stressful phases of life and are usually not a cause for concern. However, if complaints persist over a longer period or worsen significantly, medical evaluation should be sought. Professional societies generally only speak of a chronic sleep disorder when sleep problems have lasted at least three months and occur on at least three nights per week.

An elevated cortisol level is not always the cause of sleep problems. Poor sleep quality can be due to a variety of physical or psychological conditions in addition to elevated cortisol. These include depression, anxiety disorders, thyroid disorders, restless legs syndrome, chronic pain or obstructive sleep apnoea. Certain medications, alcohol, caffeine or shift work can also significantly affect the natural sleep–wake rhythm. Only rarely is a hormonal disease such as Cushing’s syndrome — in which too much cortisol is produced chronically — the reason for the complaints. If a disturbance of cortisol balance is suspected, a doctor can assess this using specific blood, saliva or urine tests.

If your sleep problems persist for several weeks or months, you feel chronically exhausted during the day, or accompanying symptoms such as loud snoring, breathing pauses, unexplained weight changes, persistently high blood pressure or marked performance decline occur, medical evaluation is advisable. The earlier possible causes are identified, the more targeted an appropriate treatment can be.

Disclaimer

This article does not replace treatment by a qualified therapist. The basis of this article is studies and current literature. It must not be used for self‑diagnosis or self‑treatment. Discuss any ideas from this article with a therapist you trust if necessary.

About the author

Katharina Korbach regularly writes blog posts for the Narayana Verlag on medicinal plants and natural active ingredients. She developed an interest in language and wrote her own literary texts from an early age. A serious illness during her final school exams led to an intensive engagement with health and nutrition topics that continues to this day. After repeated failures of conventional medical treatment methods, she decided on a more self‑empowering, naturopathic therapeutic approach. A plant‑based diet was a key element in her recovery.

References

1. O'Byrne NA, Yuen F, Butt WZ, Liu PY. Sleep and Circadian Regulation of Cortisol: A Short Review. Curr Opin Endocr Metab Res. 2021 Jun;18:178–186. doi: 10.1016/j.coemr.2021.03.011. Epub 2021 May 5. https://pmc.ncbi.nlm.nih.gov/articles/PMC8813037/.
2. Mohd Azmi NAS, Juliana N, Azmani S, Mohd Effendy N, Abu IF, Mohd Fahmi Teng NI, Das S. Cortisol on Circadian Rhythm and Its Effect on Cardiovascular System. Int J Environ Res Public Health. 2021 Jan 14. https://pmc.ncbi.nlm.nih.gov/articles/PMC7830980/.
3. Pulopulos MM, Hidalgo V, Puig-Perez S, Montoliu T, Salvador A. Relationship between Cortisol Changes during the Night and Subjective and Objective Sleep Quality in Healthy Older People. Int J Environ Res Public Health. 2020 Feb 16. https://pmc.ncbi.nlm.nih.gov/articles/PMC7068538/.
4. Hirotsu C, Tufik S, Andersen ML. Interactions between sleep, stress, and metabolism: From physiological to pathological conditions. Sleep Sci. 2015 Nov. https://pmc.ncbi.nlm.nih.gov/articles/PMC4688585/.
5. Morgan E, Schumm LP, McClintock M, Waite L, Lauderdale DS. Sleep Characteristics and Daytime Cortisol Levels in Older Adults. Sleep. 2017 May 1. https://pmc.ncbi.nlm.nih.gov/articles/PMC6251667/.
6. Łuszczak J, Kocki J. Clinical evidence for the adaptogenic effects of Withania somnifera and Rhodiola rosea – A systematic review with molecular interpretation of psychometric outcomes. Ann Agric Environ Med. 2026 Mar 25. https://pubmed.ncbi.nlm.nih.gov/41906501/.
7. Shen H, Zhang LJ, Zhu WY. The Sleep-Enhancing Effect of Lavender Essential Oil in Adults: A Systematic Review and Meta-Analysis. Holist Nurs Pract. 2026 Mar–Apr 01. https://pmc.ncbi.nlm.nih.gov/articles/PMC12904233/.
8. Cheong MJ, Kim S, Kim JS, Lee H, Lyu YS, Lee YR, Jeon B, Kang HW. A systematic literature review and meta-analysis of the clinical effects of aroma inhalation therapy on sleep problems. Medicine (Baltimore). 2021 Mar 5. https://pmc.ncbi.nlm.nih.gov/articles/PMC7939222/.
9. Yogi W, Tsukada M, Sato Y, Izuno T, Inoue T, Tsunokawa Y, Okumo T, Hisamitsu T, Sunagawa M. Influences of Lavender Essential Oil Inhalation on Stress Responses during Short-Duration Sleep Cycles: A Pilot Study. Healthcare (Basel). 2021 Jul 18. https://pmc.ncbi.nlm.nih.gov/articles/PMC8303840/.
10. Reichert CF, Deboer T, Landolt HP. Adenosine, caffeine, and sleep-wake regulation: state of the science and perspectives. J Sleep Res. 2022 Aug. https://pubmed.ncbi.nlm.nih.gov/35575450/.
11. Höhn C, Hahn MA, Gruber G, Pletzer B, Cajochen C, Hoedlmoser K. Effects of evening smartphone use on sleep and declarative memory consolidation in male adolescents and young adults. Brain Commun. 2024 May 17. https://pmc.ncbi.nlm.nih.gov/articles/PMC11154150/.