Levels of cortisol and other stress hormones are reduced both during and after meditation.
The meditator’s mood changes in a positive direction. While this indicates a lower level of general stress, the ability to react to acute stress is increased.
In recent years, stress-related sick leaves have increased. Among white-collar workers in Sweden, illness caused by stress is the most common reason for absences of over 90 days (Hälsobarometern, www.alecta.se). This diagnosis has increased from 4% of all sick leaves in 1998 to 19% in the first quarter of 2006, 27% in the age group 35–44 years. Taken together, stress, depression, back pain and burnout syndrome account for 43% of long-term sick leaves in persons below 35 years during the same period. All of these diagnoses have a probable connection to mental stress. Traditional methods of dealing with this problem seem to have met with little success.
Many people feel that meditation helps them handle stress in their daily life. In its 2003 report on burnout syndrome, the Swedish National Board of Health and Welfare referred to studies on several relaxation techniques (www. sos.se/fulltext/123/2003-123-18). It cited several claims that learning a relaxation technique provides an effective tool for stress management. “Relaxation techniques” and “meditation” comprise a variety of methods, including, on the one hand, nondirected techniques like Acem Meditation, TM and some types of mindfulness meditation, where thoughts and impulses are allowed to come and go freely while the individual focuses on a meditation sound, breathing or other meditation objects, and on the other hand concentrative relaxation techniques like autogenic training, where the person volitionally selects an exclusive focus of attention. According to the SNBHW report, all relaxation techniques have positive effects on stress symptoms, but meditation gives the best results of all.
Meditation effects can be assessed either by measuring stress hormones in the blood or by using psychologically based scales (see Hersoug’s contribution to the present volume). The main focus of the present article is on stress hormones, in other words, on biochemical measures of stress. Together with adrenaline and noradrenaline, cortisol plays a key role in the stress response (see Figure 1 on p. 79 and Factsheet 1 on p. 81). Cortisol is essential for many bodily functions (see Factsheet 2 on p. 87). Several research findings have documented that the cortisol level increases during extended periods of high stress. If high stress develops into burnout syndrome, research has indicated that communication between the brain and cortisol release from the adrenal glands is disturbed. The role of cortisol in the stress response is relatively easy to examine using blood samples.
In general, research suggests that meditation reduces cortisol levels in the blood. A few studies show no change in cortisol levels, but no studies show increased levels, which would be the case if the changes were merely random. This indicates that meditation has a positive effect on cortisol levels, and thereby on stress. It seems, too, that the effects on cortisol increase with long-term meditation practice. The studies presented in this article suggest that different types of meditation techniques may contribute to different effects on cortisol levels, though further research is required in this area.
The stress response originates in the brain and is passed on to the body through the nervous and hormonal systems, eventually producing increased blood pressure and heart rate. When a stressful situation is perceived by the brain cortex, this information is passed on to the hypothalamus, which stimulates the nervous system to release noradrenaline and the hormonal system to interact with the pituitary gland and the adrenal glands to release cortisol and adrenaline. Assisted by cortisol, noradrenaline and adrenaline serve to increase blood pressure and heart rate.
Research findings at the University of California and Stanford University in the USA in the late 1970s indicate that stress was reduced during and immediately after meditation (TM). The cortisol concentration decreased during the time the subjects were meditating and gradually returned to normal after the meditation session. Furthermore, the studies suggest that the effect was enhanced in subjects who had meditated regularly over a long period (Jevning 1978). Cortisol levels decreased more in the group that had meditated longer (3–5 years) than in the group with a shorter meditation history (3–4 months). No change was documented in the control group consisting of subjects taking ordinary rest. There were 15 subjects in each group. The control group had the opportunity to learn meditation after the study, and were examined again after 3–4 months. At this point they obtained effects comparable to the first meditation group.
In a six-week study at the Chulalongkorn University in Bangkok (Sudsuang et al. 1991), significant effects of meditation were observed in 52 male Thai students who learned a form of Buddhist meditation. The authors do not specify the exact meditation technique, but indicate that it is more like Zen meditation than transcendental meditation. In addition to cortisol, blood pressure, heart rate, breathing capacity and reaction time were also measured. The students stayed in a monastery and meditated 4 hours per day during the first three weeks followed by 2 hours per day during the last three weeks. The effect from before to after the six-week period was measured. The participants were also compared with 30 male students who lived as usual during the same period. Cortisol levels decreased significantly in the meditation group (see Figure 2). Furthermore, blood pressure decreased in all meditators, as did heart rate. Several parameters of lung function showed improvement, and reaction time was 22% faster than before the subjects learned meditation. In the control group, no changes were observed during the six weeks. The study was well designed, with a large number of participants, which supports the reliability of the results.
Figure 2. Serum cortisol levels: in one study, meditators and control subjects started at the same levels of cortisol concentration, but after three and six weeks of intense meditation, cortisol levels were significantly lower in the meditators. Cortisol levels are an indicator of stress activation.
Our stress system is an intricate network of nerve signals and hormones that are released and then influence other hormones, which in turn influence how the body functions – especially the turnover and storage of fat and carbohydrates, the flow of blood to different organs in the body and the functioning of our immune system.
The experience of stress initiates nerve signals in the brain, and these are then distributed to the entire body. This mechanism makes it possible for us to mobilise bodily reactions to meet the challenge in question. Blood pressure increases, and so does heart rate. There is increased blood flow to the muscles, and the brain is activated. This reaction is called the “fight-or-flight response”. The “stressor” may be external (e.g. a car driving directly towards us, a physical injury), or internal (for instance, anxiety about work).
The stressor triggers a defence system in the brain. The signals are communicated to the body in two ways: rapidly via the nervous system or more slowly using hormones transported by the blood (see Figure 1).
In the rapid route, nerve signals travel via the so-called sympathetic nervous system to blood vessels, the heart and adrenal glands. The hormones noradrenaline and adrenaline are then released from nerve terminals and adrenal glands. These stimulate alertness, heart rate and blood supply, and are therefore essential to our ability to fight or flee.
The slower defence system activates the hypothalamus in the brain, where the corticotropin-releasing hormone (CRH) is released. This is transported to the pituitary gland, which in turn releases adrenocorticotropic hormone (ACTH). ACTH is then transported via the blood to the adrenal glands, where cortisol is released. Cortisol is essential and performs many functions in the body (see Factsheet 2), including functions related to the stress response. This defence system is called the HPA-axis (Hypothalamus, Pituitary, Adrenals), referring to the relationship between the three organs. Burnout syndrome has a demonstrated influence on this system.
A positive impact of meditation on both psychological stress and cortisol levels was found in a study of 22 psychology students in Iowa, USA. They had meditated (TM) for a long time, 8.5 years on average (with a large variation between subjects). This group was compared with 33 other psychology students who did not practise a relaxation technique (Walton 1995). The researchers examined the urinary excretion of cortisol and a hormone called aldosterone, which, like cortisol, is excreted from the adrenal glands, and which is involved in regulating fluid balance. They also performed psychological tests (Spielberger’s State-Trait Anxiety Inventory, STAI, which measures the level of anxiety; and Profile of Mood States, POMS, which measures different aspects of mood). Both cortisol and aldosterone were significantly lower in the meditating group than in the controls. The interpretation of lower aldosterone is somewhat uncertain. The meditating subjects’ state of mind was better than that of the controls, and they had a much lower “depression – low mood” score. The authors concluded that the meditators were considerably less stressed. Interestingly, the biochemical and psychological results revealed similar trends.
Another study found evidence of greater benefits from meditation than from education in stress handling and time management. MacLean et al. (1997) found that cortisol levels decreased after 4 months of meditation practice (TM), but not after learning strategies for handling stress.
Their study also tested stress reactivity, e.g. by asking the subjects to perform subtractions and simultaneously measuring cortisol levels. The tests used may also differentiate persons with a high versus a low risk of heart disease. It turned out that the meditators’ reaction to acute stress was increased cortisol levels, while the stress education group manifested decreased cortisol.
This might be interpreted as showing that education in stress handling and time management works better than meditation, but the authors’ conclusion was the opposite. They claimed that the combination of decreased cortisol during rest and a more pronounced reaction to acute stress indicates an adaptable low stress profile in the meditation group. It is considered advantageous to react in acute situations but be able to relax in between, and this is what the meditators appeared to do. The benefits of this kind of adaptability are confirmed in other studies.
In a study comparing meditation and sports activities, both jogging and meditation improved the mood of experienced practitioners (Harte et al. 1995). Joggers and meditators were compared before and after their respective activities, in order to investigate the short-term effects of running and meditation. The study compared two groups: 11 elite runners and 12 experienced meditators who had been meditating for 6.5 years (yogi meditation: chants, breathing exercises, concentration). The groups were matched in terms of age, sex and personality. The average age was 31 years.
In addition to mood, the study also looked at levels of cortisol, beta-endorphin and corticotropin-releasing hormone (CRH, see Factsheet 1), which is associated with mood disturbances. Beta-endorphin is often called the endogenous morphine, and increased levels in the blood are related to pain relief and feelings of well-being.
In this study, in contrast to other studies, cortisol levels did not change in either joggers or meditators, possibly because the joggers were already well trained and the meditators were experienced practitioners. Beta-endorphin increased with running but not with meditation. The authors were surprised that meditation increased levels of CRH, which is assumed to be related to physical activities and associated with increased endorphin levels. The authors conclude:
“The positive effects of both running and meditation were obvious both on a subjective and endocrinological, i.e. hormonal, level. But in spite of a large degree of overlap in the results from the two activities, there were also differences in the results.” (Harte et al. 1995)
This conclusion suggests that there is much more to be understood regarding the effects of meditation and differences in effects across activities and methods.
Meditation has an impact not only on cortisol but also on the “fast” stress hormones noradrenaline and adrenaline (see Factsheet 1). Researchers in Cordoba, Spain, studied 19 individuals who had been practising meditation (TM) for at least one year, and 16 persons who had not learned any specific relaxation technique (Infante et al. 2001). They conclude that meditation has a marked effect on the sympathetic nervous system (noradrenaline) and the adrenal glands (adrenaline). The noradrenaline concentration in the blood was substantially lower both in the morning and in the evening in people who meditated. Adrenaline was also lower in the morning, but not at night. The findings can be interpreted as indicating a lower general stress level in the meditators.
Cortisol is released from the adrenal glands and has a central role in bodily functions. We cannot survive without it. If for some reason an individual lacks cortisol, as in Addison’s disease, it must be added as a supplement. Along with noradrenaline and adrenaline, cortisol regulates blood pressure as well as heart and blood vessel functions. It regulates the use of proteins, carbohydrates and fat.
During acute stress, cortisol helps to mobilise energy through glucose. It hinders inflammatory responses due to infection or injury. Cortisol is usually released into the blood in large amounts in the morning, just after we wake up. Concentrations in the blood and tissues then increase, after which the rate of release decreases, reaching its lowest point in the evening.
If cortisol levels are too high for a long period of time, the immune system will suffer. It has been shown that it is easier to acquire an infection in times of stress. The appetite increases, and so do insulin levels. Owing to increased cortisol, fat is moved to the waist, where the fat cells are more sensitive to cortisol than in other parts of the body. Muscle tissue is broken down into its building blocks (amino acids), which are in turn released into the blood and are then used by the liver to produce glucose as a source of energy.
Long-term stress can also destroy brain cells associated with memory functions. Increased cortisol levels have been connected with depressive mood states. It has been shown that waste products of cortisol can decrease serotonin levels in the brain (serotonin is a so-called transmitter between certain nerve cells), and this can cause depression. Both memory problems and depression have been identified as aspects of the burnout syndrome, in which cortisol and the HPA-axis are disturbed.
Can we draw any conclusions? During the past ten years, research dealing with hormone systems and the brain has taught us a lot about the relationship between body and mind. It is no longer viable to uphold the sharp distinction between soma and psyche that is typical of the long Western tradition initiated by Descartes. This research has made it increasingly clear that psychological factors influence the body and vice versa. Thus, it is quite likely that mental relaxation techniques like meditation may have a positive influence on the body.
Recent progress in research has increased our understanding of how meditation works on a biochemical level. However, to understand how meditation influences body and mind, we need further high-quality studies involving large numbers of participants and measuring several markers, both biochemical and psychological. In general, meditation studies involve relatively few subjects; larger samples like those in the Thai study (Sudsuang et al. 1991) are needed in order to reveal significant differences. The fewer individuals in each group, the more pronounced the differences have to be in order to be detected. This is true for studies of new drugs or medical treatments, where samples with hundreds and sometimes thousands of subjects are needed in order to produce significant indications.
Unfortunately, such studies are expensive to perform. In contrast to pharmaceutical research, which is typically paid for by commercial organisations, there is as yet not enough funding for meditation research. A neutral context and a scientifically sound selection of subjects are also important for the results to be reliable.
Hormone levels and other measures such as blood pressure are so-called biomarkers for clinical effects. Low blood pressure is not important per se, but because it decreases the risk of complications like stroke (brain infarction) and kidney damage. Likewise, a decrease in cortisol levels is not a goal in itself, but is connected to improved health. The relationship between cortisol and stress is not yet scientifically established (see Factsheet 2), but the reduced psychological and biochemical markers of stress found in scientific studies of meditation confirm the common experience that meditation has a positive impact on our ability to handle everyday stress.