What do depression, skin rashes, stomachaches, and high blood pressure have in common? They can all be symptoms of stress. And there are many other possible stress symptoms and consequences that long-term stress brings with it. If your body constantly releases stress hormones, this can cause chain reactions throughout the body and have a lasting negative impact on your well-being and health.
Chronic stress is where your body is in a constant state of emergency. Stress becomes a problem when it is long term. The regular presence of stress hormones is unnatural for the human body – and it is ill-equipped to handle stress over a longer period of time. Think about our ancestors: When hunting predators, they had an option between fight or flight responses in order to survive. These responses were usually over relatively quickly, subsequently allowing the body to rest, stress hormones to decrease, and blood pressure to drop. Symbolically, stress thus guaranteed their survival. They were also exposed to stress – but to stress of a different kind compared to today.
These days, stress that occurs in everyday working life, for example, can last much longer and become constant. In such cases, cortisol levels are also increased over the long term – and with it, pulse, blood pressure, and blood sugar. In addition, chronic stress often disturbs the quality of sleep. Combined, these stress symptoms can really mess up the body.
Read this article to find out why stress can make you ill in different ways, what the most common stress symptoms are, and how long-term stress is linked to stomach pain and intestinal health, headaches, and skin rashes.
What Is the Best Definition of “Stress?”
Just over one-fifth of people declare themselves to be very happy. The ratio is more than twice as high as for stressed people. Everybody knows the term “stress” and most people have already experienced stressful times. Stress is the human body’s reaction to a stressful situation, and this reaction is triggered by a stressor. A stressor can be any external stimulus or event which causes stress to an organism. Situations that are regarded as threatening or unpleasant can also be stressors. Disappointment, fears of failure, and low self-confidence are the most severe stressors.[3, 4]
The term “stress” has gained increasing popularity in recent years. According to a Forsa study, around 80 percent of 36- to 45-year-olds suffer from stress, in school or at university and also from financial worries. Such stress is closely linked to symptoms such as headaches, back problems, neck tension, as well as gastrointestinal problems and can, in the long run, also encourage other health conditions.
Don’t worry: Stressful times inevitably belong to our everyday lives, and success involves overcoming obstacles. Even though it is not realistic to live and work in a stress-free world, humans are able to control what they perceive as stressful and how to react to this.
Stress regulates our survival mode: It makes us alert and focused, sharpens our senses, makes us react quickly, run well, and fight. This helped our ancestors to hunt down their prey or flee from danger. In such situations, their body secreted cortisol, which made them ready to either fight or flee. In survival mode, adrenaline and cortisol flow into the body, blood pressure increases, breathing and pulse quicken, and glucose is secreted for energy supply. Digestive and immune functions are stopped so that the body can focus on the situation at hand. Even today, short phases of stress can help us perform at our best when it matters.
The balance of our metabolism and of our hormones is restored by the secretion of dopamine once the dangerous situation is over. Dopamine rewards our brains for mastering the challenge.
How Stress Affects the Body
In acutely stressful situations, stress symptoms can appear in a wide variety of ways: Headaches and a tense neck after a stressful day at work, a nervous stomach before an important exam, stomachaches after a family argument, a skin rash because of money worries. Stress – especially chronic stress – can also negatively affect our mental performance and memory.
Have you already experienced your brain processing dangers so quickly that you usually don’t even notice it yourself? For example, when a car comes towards you, you jump to the side – as if automatically – and only realize afterward what has happened.
The stress hormone cortisol also influences our immune system. Administered in high doses, it has immunosuppressant effects. This means that your immune system and thus your immune defense are restricted, as fewer T-helper cells and B lymphocytes are produced, which eliminate foreign bodies. Due to your body’s impaired defenses, there is a greater susceptibility to infection.
In medicine, however, this negative effect also has beneficial effects. Synthetically produced glucocorticoids such as prednisone are used to treat autoimmune diseases, where the immune system attacks the body’s own healthy tissue. Due to its immunosuppressant effect, the immune system’s activity is reduced which avoids further damage. In addition, it is used in allergic reactions and chronic as well as acute inflammation.
What Does Cortisol Do?
The stress hormone cortisol is a steroid hormone and belongs to the group of glucocorticoids (the most important of which are cortisol and cortisone). When the body feels stress, more cortisol is secreted. The adrenal cortex produces cortisol and otherwise has a wide variety of functions in the body. These include, among others, its influence on carbohydrate, protein and fat metabolism, blood pressure, and blood sugar. When it comes to our immune system, it also plays an important role.
The Role of Cortisol in the Body
Cortisol is a hormone that is vital for the body. It contributes to energy metabolism, mineral metabolism and blood pressure, immune defense, processing stress, cell division, and memory and brain function. Cortisol keeps us awake and alert. The function of cortisol, however, is much more widespread, as it influences many metabolic processes:
- To regulate carbohydrate, protein, and lipid metabolism
- To increase blood sugar levels by transforming amino acids into glucose
- To inhibit inflammation by reducing any inflammatory factors
- To oppress the immune system by reducing the production of antibodies
- To supply the body with energy
- To release insulin
Cortisol is especially important for carbohydrate levels due to its vital function. By releasing sugar in the form of glucose, cortisol increases blood sugar levels during the night when no food is consumed so that enough energy is available to the body. If the body produced no cortisol, this would result in nocturnal hypoglycemia, which in the worst case could lead to a coma.
Cortisol stimulates protein and lipid degradation to provide our bodies with energy. Thus, cortisol speeds up the process of degrading fatty tissue and muscles.
Where Is Cortisol Produced?
The adrenal glands are situated above the kidneys, weigh approximately five grams and are responsible for the production of several hormones. The adrenal cortex comprises three zones:
- zona glomerulosa: production of aldosterone, responsible for the long-term regulation of blood pressure
- zona fasciculata: responsible for producing glucocorticoids
- zona reticularis: produces male and female sex hormones
Cortisol is the most important glucocorticoid which is produced in the zona fasciculata. For cortisol to be produced, cholesterol and the peptide hormone adrenocorticotropic hormone (ACTH) are needed. ACTH is secreted by the pituitary gland and activates the production of glucocorticoids in the adrenal glands. When in a stressful situation, ACTH is released.
The concentration of cortisol is subject to natural fluctuations, which is typical of hormones. The concentration of the hormone depends on the time of day. The following infographic shows you ideal cortisol levels throughout the day. Cortisol levels are highest in the morning between 6 and 9 a.m. This is because the body is preparing for any stressful situations that might come up during the day. Over the course of the day, cortisol levels decrease and reach their low point around midnight. Cortisol is secreted in seven to ten peaks; therefore, the concentration cannot be determined by just one single sample at one point of the day.
Even though hormones are subject to natural fluctuations, certain factors can lead to low cortisol levels or high cortisol levels.
High Cortisol Levels
What Causes Excess Cortisol Levels?
High cortisol levels in the morning are pretty normal – as long as they remain within a certain range. Should, however, high cortisol levels occur throughout the day, this may be caused by the following health issues:[7, 12, 13]
- Cushing’s disease
- birth control pills, drugs containing glucocorticoids
- obesity or anorexia
- burn injuries
Cushing’s disease leads to increased cortisol levels. These can be caused by an excessive dosage of drugs containing glucocorticoids or by tumors, which produce more of the adrenocorticotropic hormone (ACTH). ACTH stimulates the adrenal cortex to produce cortisol. As soon as ACTH is released in excess, cortisol synthesis increases drastically. This results in several disorders, which are caused by excess cortisol.
Permanent stress and depression are also main causes for high cortisol levels. In stressful situations, an appropriate amount of cortisol is normally secreted to bring the body into survival mode. If you suffer from stress more often and especially high stress, too much cortisol is produced.[8, 15]
Due to certain instances, such as pregnancy or alcoholism, Pseudo-Cushing’s syndrome can occur. With this syndrome, elevated values do not result from natural conditions. Obesity, infection, anorexia, acute psychosis, intake of birth control pills, or burn injuries can also increase cortisol levels.[15, 16]
What Are Typical Stress Symptoms?
Symptoms commonly observed when people are under stress include:[17–20]
- Stomach pain, diarrhea, and other digestive problems
- Skin rash and other skin problems – for example, acne
- Headaches and back, neck, and joint pain
- Palpitations and dizziness
- Tiredness, fatigue, and sleep problems
In addition to these relatively immediate symptoms, there are also long-term consequences that chronic stress can trigger. The best-researched are the connections with the cardiovascular system – stress has an effect on blood pressure and pulse rate, among other things, and many studies confirm that there is an obvious connection.
Other possible long-term consequences of long-term stress are:
- Mental illnesses such as depression, burnout, anxiety disorders
- Poor concentration and chronic fatigue
- Obesity and diabetes
- Susceptibility to infection
Besides some evidence that suggests stress is related to ringing in the ears and tinnitus, other studies additionally found that people who are under chronic stress are likely to have more upper respiratory infections, such as flu or colds. Researchers therefore suspect that stress can weaken the immune system in the long run.
In addition to the above-mentioned symptoms, high cortisol levels – that is, high stress levels, can affect the healing of wounds and the incorporation of nutrients into the bones. This increases the risk of developing osteoporosis (bone loss), which may result in bone pain and fractures. Several studies also found a correlation between elevated cortisol levels and depression. Increased cortisol secretion leads to less fat burned – in order words, weight gain. Moreover, people with high cortisol levels may experience skin changes, high blood pressure, and high blood sugar values.
In women, elevated cortisol levels can also lead to thicker or more visible body and facial hair (hirsutism), irregular or absent menstrual periods and in men to impotence, loss of libido, and fertility.
Can Stress Cause Stomach Pain?
Symptoms in the digestive tract, such as stomach pain, constipation, and diarrhea, are particularly typical of stress. The fact that the psyche can affect the stomach probably comes as little surprise to you. You have probably experienced for yourself the sensation of butterflies in your stomach when you are nervous or anxious about exams or stage fright.
In fact, there is a close connection between the psyche and the digestive tract – that is, the gut. It is not for nothing that we speak of the gut as the body’s second brain. Among other things, the intestines and the brain constantly communicate with each other via the vagus nerve, one of the largest nerves in the body. For example, your digestive tract can let you know when you have eaten something bad. The brain reacts by giving you nausea and a nausea stimulus to get rid of the toxins.
In recent years, it has become increasingly clear what role the gut flora or gut microbiome plays in this. The trillions of bacteria in the gut are involved in communication with the brain. Some studies have shown that chronic stress can influence the composition of the gut flora and possibly upset the balance between good gut bacteria such as the lactobacilli and bifidobacteria and bad bacteria. The good news is that you may be able to alleviate your symptoms by strengthening your gut flora. In animal studies, this has already worked: Mice that were given certain lactobacilli and bifidobacteria were able to react better to stress. If this also proves true for humans, targeted probiotics, prebiotics, and dietary changes could help treat stress and depression in the future.
Did you know that if you add up all the trillions of tiny organisms in your gut, they weigh about as much as your brain?
Stress and Irritable Bowel Syndrome
Some studies have shown, for example, that long-term stress can increase the pain of irritable bowel syndrome (IBS) and other inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis.[25, 27] In general, chronic stress seems to influence the perception of pain. People who are constantly under stress perceive more pain in conditions like IBS – in some cases, stress may even be a trigger for chronic pain syndromes.
Have you also heard that people get stomach ulcers from stress? It's actually not that simple. Stomach ulcers are usually caused by infections with bacteria like Helicobacter pylori or by taking too many painkillers. However, stress and other lifestyle factors, such as alcohol consumption, can possibly increase the risk of ulcers and make the symptoms worse.
Headaches Due to Stress
The link between stress and headaches has been investigated in numerous studies over the past decades. It is still not entirely clear if stress is a cause of headaches or if people who have frequent headaches perceive their stress more intensely. Needless to say, there are still many questions that remain unanswered when it comes to stress symptoms such as headaches.
In a German study with more than 5,000 test participants, for example, people had more frequent and more severe headaches the more intensely they felt stress. In the case of migraines, the connection was even clearer. Other studies also showed that stress could be a trigger for headaches and even the development of chronic headaches.
Some researchers now suspect that measures to reduce stress could also have a positive effect on people with constant headaches. For example, if you suffer from chronic headaches and you specifically watch out for stressful situations, you might be able to react better and use relaxation techniques or other measures early on.
Skin Conditions Caused by Stress and Anxiety
This link between stress and the appearance of our skin has also been well studied. A skin rash, for example, is a symptom often reported by people who are stressed. Stress can also be a trigger for skin diseases that occur in episodes, such as atopic dermatitis, psoriasis, and rosacea. The effect of stress on the skin is already evident in adolescents – in studies, psychological stress, including exam stress, worsened the symptoms of acne in teenagers.[33, 34]
Chronic stress may also be a cause of acne outbreaks in adults. This is due to the hormonal changes caused by stress. This includes the increased release of androgens. These sex hormones stimulate the hair follicles and sebaceous glands in the skin, which can cause acne outbreaks. With stress-related skin problems, it often makes sense to tackle the causes – that is, the stress and the skin problems in equal measure, ideally with the help of a dermatologist.
Cortisol, Diabetes, and Obesity
Diabetes is a blood sugar disease, which leads to impaired insulin production and fluctuations in blood sugar levels.
Under stress, cortisol levels rise and lead to increased sugar secretion. Blood sugar levels rise. This causes the pancreas to secrete a greater amount of insulin. If the pancreas has to permanently struggle against elevated blood sugar levels, this can lead to diabetes in the long run. Due to an excess supply of insulin, the receptors that process insulin react less and less sensitively to it. This can lead to insulin resistance and type 2 diabetes.
A large-scale study with 160,000 professionals also revealed a correlation between elevated cortisol levels and obesity. However, the current study situation is still very contradictory.
It is assumed that increased cortisol levels lead to changes in the fat cells. The mature fat cells (adipocytes) are produced from their precursors, the preadipocytes. In contrast to the preadipocytes, the adipocytes store fat. This can lead to weight gain.
Can Low Cortisol Cause Depression?
In the United Kingdom, 19 percent of people claim they are depressed according to a survey conducted with 5,000 adults by the National Centre of Social Research. Furthermore, according to an article in the Pharmazeutische Zeitung (German pharmaceutical trade journal), people with depression have elevated cortisol levels. It is assumed that this is caused by a physiological dysfunction, which suppresses the hormones normally needed to avoid high cortisol levels.
More and more studies indicate that depression is a stress disorder, as there seems to be a strong correlation between the two. An epidemiologic study associated early negative social factors with a higher risk of developing depression. These factors included natural disasters, physical violence, or sexual abuse. Changes in one’s personal environment or negative events are another risk factor triggering depressive episodes. Depression is assumed to correlate with the secretion of the stress hormone cortisol. High cortisol levels can in the long run lead to fat deposits in the blood vessels and thus lead to arteriosclerosis. For this reason, depressed people have an increased risk of developing cardiovascular diseases.
How Can I Optimize My Cortisol Levels?
A visit to the doctor is the traditional way of testing your cortisol levels. However, this involves long waiting periods, which causes you unnecessary stress and results may therefore be slightly affected by this. In order to save you the waiting time, cerascreen has developed a cortisol test you can take within the comfort of your home.
Measuring cortisol is simple. With the cerascreen® Cortisol Test, you can test your cortisol levels from home. The self-test creates a day profile, which illustrates the times at which your cortisol levels are high (more specifically, when your stress is highest). For the laboratory analysis, seven saliva samples are needed, which have to be taken within 12 hours. As the values fluctuate during the morning, one average value of the first three samples is determined. This average value then represents the morning value.
The majority of cortisol in the blood is (protein)bound. Approximately one to three percent are free. Only the free form is the active form. It is secreted into saliva and can be measured in it. As cortisol levels change under stress, taking saliva samples at home is the most stress-free way to analyze your cortisol levels.[42, 43]
Treating High Cortisol Levels
Once you have recognized that chronic stress is the cause of many of your problems, you can try to counteract it in a targeted way.
Stressful situations and phases cannot be avoided in life. But you can learn to react to them in a healthy way and restore a balance in your life. One piece of advice that psychologists often give is to make sure that you do something nice at least once a day and have a little time for yourself – whether you undertake a hobby you enjoy, read a book, or watch an episode of your favorite series.
Being happy makes you healthy. Researchers from Canada investigated the connection between positive feelings and the development and risk factors of cardiovascular diseases in more than 1,700 test participants over ten years. The results were as follows: Less stress and more positive feelings reduced the risk of developing coronary heart disease.
How to Lower Cortisol Levels Naturally
Apart from successful therapy or curing the underlying disease, which help to regulate stress, there are further ways to restore healthy cortisol levels – without drugs.
- Give your body the chance to regenerate! Sufficient high-quality sleep helps to reduce stress.
- Do sport! Sport helps to relieve stress and can optimize cortisol levels.
- Allow time for relaxation! For example, use stress management techniques.
- Take time to spend time with important people on a regular basis! By doing this, you activate the feel-good hormone oxytocin. It is released as a result of physical contact and lets your cortisol levels recover.
How to Lower Cortisol Levels By Your Diet
Your diet alone can work wonders when it comes to fighting elevated but also low cortisol levels. We have listed some scientifically proven nutritional advice to help you manage your cortisol levels:
Take vitamin B
Vitamin B complex, especially vitamin B6 and folic acid, help to reduce work stress and improve your mood. Legumes, fish, walnuts, yeast, and soy are rich in these vitamins.
Reduce coffee consumption
Coffee increases your cortisol levels.
Drink black tea
Black tea lowers your cortisol levels. However, please don’t drink tea if you have been advised to avoid it on medical grounds.
Eat dark chocolate
Dark chocolate doesn’t only contain antioxidants; it also reduces cortisol levels.
Fish is rich in omega-3 fatty acids, which reduce the cortisol levels in your body. This is especially the case for mackerel, herring, and salmon. Some vegetable oils like rapeseed oil and soybean oil also contain larger amounts of omega-3 fatty acids.
Boost your zinc levels
Zinc reduces the secretion of cortisol. Oysters contain lots of zinc. Edam and Emmental cheese, as well as chicken eggs, are also ideal sources of zinc.
To find out more about zinc and its health benefits, head over to our dedicated article.
Optimize your vitamin C levels
Peppers, citrus fruits, and berries are rich in vitamin C. It helps to regulate cortisol levels. Eat them fresh, as vitamin C is unstable and is easily broken down by heat and exposure to sunlight.
Did you know that licorice and one of its ingredients, glycyrrhetic acid, can actually increase cortisol levels? Pregnant women should refrain from eating licorice, as the embryo cannot counter this influence. People who take anticoagulants should only eat licorice in smaller quantities or better avoid it, as it contains vitamin K.
Cortisol and Dark Chocolate
Eating chocolate makes us happy – it is undoubtedly a hero in stressful times. Some experts have revealed that the flavonoids contained in dark chocolate, which belong to the antioxidants, inhibit the secretion of cortisol and adrenaline. In 2014, a study investigated the effects of dark chocolate on cortisol levels. One-half of study participants ate half a bar of chocolate and the other half, the placebo group, ate chocolate without flavonoids. Afterward, they all had to pass a stress test. For the participants that ate dark chocolate, the levels of the stress hormones cortisol and adrenaline increased at a slower rate. Thus, the higher the flavonoid blood levels, the smaller the increase of stress hormones.
Antioxidants are known for their radical scavenging activities. Due to their chemical bond, they can slow down or even stop oxidation of other substances. Antioxidants occur in nature, but due to their positive health effects, they are increasingly synthetically made. The most well-known antioxidants are vitamin C, vitamin E, micronutrients such as zinc and selenium, carotenoids, and beta-carotene.
To find out more about the health benefits of chocolate, head over to our dedicated Health Portal article.
How Do You Relieve Stress Quickly?
For some, drinking a cup of tea and reading a book already helps to come to rest. For others, a punching bag or other sports help to relax. All of these have in common that they improve subjective stress perception but they don’t tackle the problem at source to reduce cortisol levels in the long run. Certain targeted relaxation techniques, often paired with exercise, have been shown to lower stress levels. This has a positive influence on not only your mind but also physiological factors such as your blood pressure, pulse, and breathing rate.
These relaxation techniques include yoga, tai chi, autogenic training, and progressive muscle relaxation, but also other types of meditation and mindfulness training. Some of these techniques are easy and quick to learn – for example via online videos. Others need some practice and coaching, but the good news is that most people can benefit from them after a short time.
Studies furthermore reveal that regular physical activity can reduce stress and lower the risk of depression and anxiety. At the same time, exercise improves your cardiovascular health and thus counteracts possible long-term consequences of chronic stress.
How Does Socializing Help Mental Health?
Our social environment is crucial to how we experience stress. Studies have repeatedly shown that people who receive a lot of support from friends and acquaintances, family, partners, and colleagues are better able to react to stress and crises.[55, 56].
When you are under stress and pressure at work, it can help, for example, to meet colleagues regularly for a chat and to let off a little steam about the job. This also works if you are working from home. Just meet up for a digital coffee break via video call every now and then.
In any case, research shows for people of all ages that when we feel supported by people around us, well-being and general physical and mental health increase.
How to Lower Cortisol Levels through Medication
Medication is only used if cortisol is needed permanently – that is, over a lifetime – and no other therapy can help like, for example, in people with Addison’s disease or Cushing’s disease. For a long time, the drugs metyrapone, aminoglutehimide, mifepriston, and ketoconazole have been used. They lower cortisol levels by inhibiting the enzyme needed for the synthesis of steroids.[58, 59]
Stress Symptoms – at a Glance
Why Does Stress Make You Ill?
Stress is your body’s reaction to situations that it perceives as a threat. It releases the stress hormones adrenaline and cortisol, thereby increasing blood pressure, pulse, and breathing rate, among other things. With chronic stress, the stress hormone levels are also constantly elevated. This upsets the body’s functions, affecting the cardiovascular system, digestion, and psyche in particular.
What Are the Common Symptoms of Stress?
Chronic stress can affect the whole body. Acute symptoms include digestive problems such as stomach pain and diarrhea, skin rashes and acne, headaches, back pain, as well as exhaustion and sleep problems.
Possible long-term consequences of chronic stress are an increased risk of cardiovascular diseases, obesity, type 2 diabetes, and poor concentration. Mental illnesses such as depression and anxiety disorders can also occur.
What Can I Do About Stress Symptoms?
Some consequences of stress should be treated by a doctor – for example, high blood pressure, depression, and chronic skin changes.
Otherwise, it is of course worthwhile to counteract stress as the cause of the symptoms. You should therefore introduce stress management techniques in your everyday life, such as relaxation techniques, physical activity, and socializing.
 Harvard Health Publishing, „Understanding the stress response“, Harvard Health. https://www.health.harvard.edu/staying-healthy/understanding-the-stress-response (zugegriffen Juni 23, 2020).
 tk-stressstudie-2016-data.pdf, https://www.tk.de/resource/blob/2026630/9154e4c71766c410dc859916aa798217/tk-stressstudie-2016-data.pdf
 Axe, J.: Dreck macht gesund: der durchlässige Darm als Ursache Ihrer Beschwerden und was Sie dagegen tun können. Piper, München (2017)
 Faller, H., Lang, H.: Medizinische Psychologie und Soziologie. Springer Berlin Heidelberg, Berlin, Heidelberg (2016)
 Stress-Aktuelle Bevölkerungsbefragung: AusmaUrsachen und Auswirkungen von Stress in Deutschland, https://www.vdma.org/documents/105628/244511/TK_Studie%20Stress.pdf/15ff404a-1799-457f-81cc-1bd640f8f56f
 Faller, Adolf; Schünke, Michael: Der Körper des Menschen - Einführung in Bau und Funktion. Thieme
 Heinrich et al. (2014).: Biochemie und Pathobiochemie. Springer-Verlag, Berlin Heidelberg
 Schwab, M.: Encyclopedia of Cancer. Springer Science & Business Media (2011)
 Gatti et al. (2009): Cortisol assays and diagnostic laboratory procedures in human biological fluids. Clinical Biochemistry. 42: 1205-1217.
 Nussey, S., Whitehead, S.: The adrenal gland. BIOS Scientific Publishers (2001)
 Rehner, G., Daniel, H.: Biochemie der Ernährung. Spektrum Akad. Verl, Heidelberg (2010)
 Addison’s disease - Symptoms and causes, http://www.mayoclinic.org/diseases-conditions/addisons-disease/symptoms-causes/syc-20350293
 Pschyrembel Online | Morbus Cushing, https://www.pschyrembel.de/Morbus%20Cushing/K05EF/doc/
 Kleine, B., Rossmanith, W.: Hormone und Hormonsystem - Lehrbuch der Endokrinologie. Springer Berlin Heidelberg, Berlin, Heidelberg (2014)
 Heinrich, P.C., Müller, M., Graeve, L., Löffler, G., Petrides, P.E. eds: Löffler/Petrides Biochemie und Pathobiochemie. Springer, Berlin Heidelberg (2014)
 N. M. Graham, R. M. Douglas, und P. Ryan, „Stress and acute respiratory infection“, Am. J. Epidemiol., Bd. 124, Nr. 3, S. 389–401, Sep. 1986, doi: 10.1093/oxfordjournals.aje.a114409.
 D. D’Amico u. a., „Stress and chronic headache“, J Headache Pain, Bd. 1, Nr. Suppl 1, S. S49–S52, Dez. 2000, doi: 10.1007/s101940070026.
 R. D. Kocalevent, A. Hinz, E. Brähler, und B. F. Klapp, „Determinants of fatigue and stress“, BMC Res Notes, Bd. 4, S. 238, Juli 2011, doi: 10.1186/1756-0500-4-238.
 A. Pedersen, R. Zachariae, und D. H. Bovbjerg, „Influence of psychological stress on upper respiratory infection--a meta-analysis of prospective studies“, Psychosom Med, Bd. 72, Nr. 8, S. 823–832, Okt. 2010, doi: 10.1097/PSY.0b013e3181f1d003.
 P. J. Gianaros und J. R. Jennings, „Host in the Machine: A Neurobiological Perspective on Psychological Stress and Cardiovascular Disease“, Am Psychol, Bd. 73, Nr. 8, S. 1031–1044, Nov. 2018, doi: 10.1037/amp0000232.
 American Psychological Association, „How stress affects your health“, https://www.apa.org. https://www.apa.org/helpcenter/stress-facts (zugegriffen Juni 24, 2020).
 J. F. Cryan u. a., „The Microbiota-Gut-Brain Axis“, Physiol. Rev., Bd. 99, Nr. 4, S. 1877–2013, 01 2019, doi: 10.1152/physrev.00018.2018.
 J. A. Foster, L. Rinaman, und J. F. Cryan, „Stress & the gut-brain axis: Regulation by the microbiome“, Neurobiol Stress, Bd. 7, S. 124–136, Dez. 2017, doi: 10.1016/j.ynstr.2017.03.001.
 S. Windgassen, R. Moss-Morris, J. Chilcot, A. Sibelli, K. Goldsmith, und T. Chalder, „The journey between brain and gut: A systematic review of psychological mechanisms of treatment effect in irritable bowel syndrome“, Br J Health Psychol, Bd. 22, Nr. 4, S. 701–736, 2017, doi: 10.1111/bjhp.12250.
 B. Greenwood-Van Meerveld und A. C. Johnson, „Stress-Induced Chronic Visceral Pain of Gastrointestinal Origin“, Front Syst Neurosci, Bd. 11, Nov. 2017, doi: 10.3389/fnsys.2017.00086.
 R. J. A. Cámara, R. Ziegler, S. Begré, A. M. Schoepfer, R. von Känel, und Swiss Inflammatory Bowel Disease Cohort Study (SIBDCS) group, „The role of psychological stress in inflammatory bowel disease: quality assessment of methods of 18 prospective studies and suggestions for future research“, Digestion, Bd. 80, Nr. 2, S. 129–139, 2009, doi: 10.1159/000226087.
 National Health Services (NHS), „Stomach ulcer - Causes“, nhs.uk, Okt. 23, 2017. https://www.nhs.uk/conditions/stomach-ulcer/causes/ (zugegriffen Juni 24, 2020).
 S. H. Schramm u. a., „The association between stress and headache: A longitudinal population-based study“, Cephalalgia, Bd. 35, Nr. 10, S. 853–863, Sep. 2015, doi: 10.1177/0333102414563087.
 D. C. Buse und R. B. Lipton, „Primary headache: What’s stress got to do with it?:“, Cephalalgia, Jan. 2015, doi: 10.1177/0333102414567382.
 G. A. B. Saif u. a., „Association of psychological stress with skin symptoms among medical students“, Saudi Med J, Bd. 39, Nr. 1, S. 59–66, Jan. 2018, doi: 10.15537/smj.2018.1.21231.
 D. D’Amico u. a., „Stress and chronic headache“, J Headache Pain, Bd. 1, Nr. Suppl 1, S. S49–S52, Dez. 2000, doi: 10.1007/s101940070026.
 G. Yosipovitch u. a., „Study of psychological stress, sebum production and acne vulgaris in adolescents“, Acta Derm. Venereol., Bd. 87, Nr. 2, S. 135–139, 2007, doi: 10.2340/00015555-0231.
 A. Chiu, S. Y. Chon, und A. B. Kimball, „The response of skin disease to stress: changes in the severity of acne vulgaris as affected by examination stress“, Arch Dermatol, Bd. 139, Nr. 7, S. 897–900, Juli 2003, doi: 10.1001/archderm.139.7.897.
 American Academy of Dermatology, „Adult acne“. https://www.aad.org/public/diseases/acne/really-acne/adult-acne (zugegriffen Juni 25, 2020).
 De Sanctis, V., Soliman, A., Yassin, M., Garofalo, P.: Cortisol levels in central adrenal insufficiency: light and shade. Pediatr. Endocrinol. Rev. PER. 12, 283–289 (2015)
 Kasper, H., Burghardt, W.: Ernährungsmedizin und Diätetik. Elsevier, Urban & Fischer, München (2014)
 Nyberg, S.T., Heikkilä, K., Fransson, E.I., Alfredsson, L., De Bacquer, D., Bjorner, J.B., Bonenfant, S., Borritz, M., Burr, H., Casini, A., Clays, E., Dragano, N., Erbel, R., Geuskens, G.A., Goldberg, M., Hooftman, W.E., Houtman, I.L., Jöckel, K.-H., Kittel, F., Knutsson, A., Koskenvuo, M., Leineweber, C., Lunau, T., Madsen, I.E.H., Hanson, L.L.M., Marmot, M.G., Nielsen, M.L., Nordin, M., Oksanen, T., Pentti, J., Rugulies, R., Siegrist, J., Suominen, S., Vahtera, J., Virtanen, M., Westerholm, P., Westerlund, H., Zins, M., Ferrie, J.E., Theorell, T., Steptoe, A., Hamer, M., Singh-Manoux, A., Batty, G.D., Kivimäki, M., for the IPD-Work Consortium: Job strain in relation to body mass index: pooled analysis of 160 000 adults from 13 cohort studies: Job strain and body mass index. J. Intern. Med. 272, 65–73 (2012). doi:10.1111/j.1365-2796.2011.02482.x
 Incollingo Rodriguez, A.C., Epel, E.S., White, M.L., Standen, E.C., Seckl, J.R., Tomiyama, A.J.: Hypothalamic-pituitary-adrenal axis dysregulation and cortisol activity in obesity: A systematic review. Psychoneuroendocrinology. 62, 301–318 (2015). doi:10.1016/j.psyneuen.2015.08.014
 45 HSE2014-Ch2-Mental-health-problems.pdf, http://healthsurvey.hscic.gov.uk/media/37739/HSE2014-Ch2-Mental-health-problems.pdf
 Hajszan, T., Dow, A., Warner-Schmidt, J.L., Szigeti-Buck, K., Sallam, N.L., Parducz, A., Leranth, C., Duman, R.S.: Remodeling of Hippocampal Spine Synapses in the Rat Learned Helplessness Model of Depression. Biol. Psychiatry. 65, 392–400 (2009). doi:10.1016/j.biopsych.2008.09.031
 Kalman, B.A., Grahn, R.E.: Measuring Salivary Cortisol in the Behavioral Neuroscience Laboratory. J. Undergrad. Neurosci. Educ. 2, A41–A49 (2004)
 Halwachs-Baumann, G.: Labormedizin. Springer Vienna, Vienna (2011)
 K. W. Davidson, E. Mostofsky, und W. Whang, „Don’t worry, be happy: positive affect and reduced 10-year incident coronary heart disease: the Canadian Nova Scotia Health Survey“, Eur. Heart J., Bd. 31, Nr. 9, S. 1065–1070, Mai 2010, doi: 10.1093/eurheartj/ehp603.
 Camfield, D.A., Wetherell, M.A., Scholey, A.B., Cox, K.H.M., Fogg, E., White, D.J., Sarris, J., Kras, M., Stough, C., Sali, A., Pipingas, A.: The Effects of Multivitamin Supplementation on Diurnal Cortisol Secretion and Perceived Stress. Nutrients. 5, 4429–4450 (2013). doi:10.3390/nu5114429
 Lovallo, W.R., Farag, N.H., Vincent, A.S., Thomas, T.L., Wilson, M.F.: Cortisol responses to mental stress, exercise, and meals following caffeine intake in men and women. Pharmacol. Biochem. Behav. 83, 441–447 (2006). doi:10.1016/j.pbb.2006.03.005
 Steptoe, A., Gibson, E.L., Vuononvirta, R., Williams, E.D., Hamer, M., Rycroft, J.A., Erusalimsky, J.D., Wardle, J.: The effects of tea on psychophysiological stress responsivity and post-stress recovery: a randomised double-blind trial. Psychopharmacology (Berl.). 190, 81–89 (2007). doi:10.1007/s00213-006-0573-2
 Martin, F.-P.J., Rezzi, S., Peré-Trepat, E., Kamlage, B., Collino, S., Leibold, E., Kastler, J., Rein, D., Fay, L.B., Kochhar, S.: Metabolic effects of dark chocolate consumption on energy, gut microbiota, and stress-related metabolism in free-living subjects. J. Proteome Res. 8, 5568–5579 (2009). doi:10.1021/pr900607v
 Barbadoro, P., Annino, I., Ponzio, E., Romanelli, R.M.L., D’Errico, M.M., Prospero, E., Minelli, A.: Fish oil supplementation reduces cortisol basal levels and perceived stress: a randomized, placebo-controlled trial in abstinent alcoholics. Mol. Nutr. Food Res. 57, 1110–1114 (2013). doi:10.1002/mnfr.201200676
 Brandão-Neto, J., de Mendonça, B.B., Shuhama, T., Marchini, J.S., Pimenta, W.P., Tornero, M.T.: Zinc acutely and temporarily inhibits adrenal cortisol secretion in humans. A preliminary report. Biol. Trace Elem. Res. 24, 83–89 (1990). doi:10.1007/BF02789143
 Methlie, P., Husebye, E.E.S., Hustad, S., Lien, E.A., Løvås, K.: Grapefruit juice and licorice increase cortisol availability in patients with Addison’s disease. Eur. J. Endocrinol. 165, 761–769 (2011). doi:10.1530/EJE-11-0518
 Ernährungsumschau: Dunkle Schokolade hilft gegen Stress, https://www.ernaehrungs-umschau.de/news/14-04-2014-dunkle-schokolade-hilft-gegen-stress/
 Freie Radikale und Antioxidantien in der Herzchirurgie, http://www.kup.at/kup/pdf/4552.pdf
 C. Herbert, F. Meixner, C. Wiebking, und V. Gilg, „Regular Physical Activity, Short-Term Exercise, Mental Health, and Well-Being Among University Students: The Results of an Online and a Laboratory Study“, Front Psychol, Bd. 11, Mai 2020, doi: 10.3389/fpsyg.2020.00509.
 M. Ioannou, A. P. Kassianos, und M. Symeou, „Coping With Depressive Symptoms in Young Adults: Perceived Social Support Protects Against Depressive Symptoms Only Under Moderate Levels of Stress“, Front Psychol, Bd. 9, Jan. 2019, doi: 10.3389/fpsyg.2018.02780.
 B. N. Uchino, K. Bowen, M. Carlisle, und W. Birmingham, „Psychological Pathways Linking Social Support to Health Outcomes: A Visit with the “Ghosts” of Research Past, Present, and Future“, Soc Sci Med, Bd. 74, Nr. 7, S. 949–957, Apr. 2012, doi: 10.1016/j.socscimed.2011.11.023.
 K. L. Siedlecki, T. A. Salthouse, S. Oishi, und S. Jeswani, „The Relationship Between Social Support and Subjective Well-Being Across Age“, Soc Indic Res, Bd. 117, Nr. 2, S. 561–576, Juni 2014, doi: 10.1007/s11205-013-0361-4.
 Aktories, K., Forth, W. eds: Allgemeine und spezielle Pharmakologie und Toxikologie: für Studenten der Medizin, Veterinärmedizin, Pharmazie, Chemie und Biologie sowie für Ärzte, Tierärzte und Apotheker ; mit 305 Tabellen ; [Plus im Web, mediscript]. Elsevier, Urban & Fischer, München (2013)
 Pharmazeutische Zeitung online: Nebennieren: Über-, Unter- und Fehlfunktionen, https://www.pharmazeutische-zeitung.de/index.php?id=57424
 Luippold, G.: Fallbuch Pharmakologie: 100 Fälle aktiv bearbeiten. Georg Thieme Verlag (2012)Cortisol und Cortison, https://derstandard.at/2694601/Cortisol-und-Cortison
 Definition of Cortisol, https://www.medicinenet.com/script/main/art.asp?articlekey=2850
 Ciriaco, M., Ventrice, P., Russo, G., Scicchitano, M., Mazzitello, G., Scicchitano, F., Russo, E.: Corticosteroid-related central nervous system side effects. J. Pharmacol. Pharmacother. 4, S94–S98 (2013). doi:10.4103/0976-500X.120975
 Hannibal, K.E., Bishop, M.D.: Chronic Stress, Cortisol Dysfunction, and Pain: A Psychoneuroendocrine Rationale for Stress Management in Pain Rehabilitation. Phys. Ther. 94, 1816–1825 (2014). doi:10.2522/ptj.20130597
 4042-stress-modern-britain.pdf, https://www.physoc.org/sites/default/files/press-release/4042-stress-modern-britain.pdf
 Straub, R.H. ed: Spezielle Pathophysiologie: mit 20 Tabellen. Vandenhoeck & Ruprecht, Göttingen (2007)
 Gatti, R., Antonelli, G., Prearo, M., Spinella, P., Cappellin, E., De Palo, E.F.: Cortisol assays and diagnostic laboratory procedures in human biological fluids. Clin. Biochem. 42, 1205–1217 (2009). doi:10.1016/j.clinbiochem.2009.04.011
 Shields, G.S., Bonner, J.C., Moons, W.G.: Does cortisol influence core executive functions? A meta-analysis of acute cortisol administration effects on working memory, inhibition, and set-shifting. Psychoneuroendocrinology. 58, 91–103 (2015). doi:10.1016/j.psyneuen.2015.04.017
 Prins, J.T., Gazendam-Donofrio, S.M., Tubben, B.J., van der Heijden, F.M.M.A., van de Wiel, H.B.M., Hoekstra-Weebers, J.E.H.M.: Burnout in medical residents: a review. Med. Educ. 41, 788–800 (2007). doi:10.1111/j.1365-2923.2007.02797.x
 Heinrichs, M., Baumgartner, T., Kirschbaum, C., Ehlert, U.: Social support and oxytocin interact to suppress cortisol and subjective responses to psychosocial stress. Biol. Psychiatry. 54, 1389–1398 (2003)
 Stresshormonregulation und Depressionsrisiko – Perspektiven für die antidepressive Behandlung, https://www.mpg.de/4752810/Antidepressive_Behandlung?c=5732343
 Waller, C., Bauersachs, J., Hoppmann, U., Höch, J., Krause, S., Szabo, F., Engler, H., Rottler, E., Herrmann-Lingen, C., Gündel, H.: Blunted Cortisol Stress Response and Depression-Induced Hypocortisolism Is Related to Inflammation in Patients With CAD. J. Am. Coll. Cardiol. 67, 1124–1126 (2016). doi:10.1016/j.jacc.2015.12.031
 N. M. Devanarayana und S. Rajindrajith, „Association between constipation and stressful life events in a cohort of Sri Lankan children and adolescents“, J. Trop. Pediatr., Bd. 56, Nr. 3, S. 144–148, Juni 2010, doi: 10.1093/tropej/fmp077.