Stress is the body and brain’s response to any sort of challenging situation, either from environmental factors (a threat or potential threat) or from internal factors such as memories. The stress system has two responses to stress. The immediate response is driven by the corticotropin-releasing hormone (CRH) and the response of the sympathetic and hypothalamic-pituitary-adrenal (HPA) axis, which releases cortisol, adrenaline, and noradrenaline into the body. The slower response is also mediated by corticosteroids and facilitates behavioral adaptation and energy storage. Neurotransmitters in the brain such as dopamine, acetylcholine, glutamate, and GABA regulate these stress responses. Specific brain areas are also involved, especially the prefrontal cortex, the amygdala, the hippocampus, the nucleus accumbens, and the hypothalamus. The interaction between these hormones, neurotransmitters, and brain areas contributes to the body’s response to stress.
Fight, flight, or freeze
The stress response affects systems throughout the body. When the brain perceives a threat, it stimulates the sympathetic and HPA systems to fill the body with corticosteroids, adrenaline, and noradrenaline which throws the body into its “fight, flight, or freeze” response. This means that the body is primed to react to the threat in the most efficient way possible and it affects systems throughout the body:
- the heart beats faster to get more blood to the muscles
- breathing rate increases to get more oxygen into the blood
- hearing becomes better
- pupils dilate to improve sight (peripheral vision is also improved)
- mental activity and alertness is increased so that decisions can be made faster
- extra clotting factors in the blood in case of injury
- sugars and fats are converted into energy for the muscles
- sweating increases and skin can become pale as blood is sent to the muscles
- less saliva
- digestion is halted as blood is diverted to the muscles
- the spleen empties red blood cells into circulation
All of these bodily changes are specialized to allow you to get away, or attack, the threat in the environment and survive. This made sense when humans first evolved, and can still be adaptive now when we are exposed to specific threats that can be dealt with by the fight, flight, or freeze response. This isn’t necessarily only for situations that contain physical threats, but this response can also improve performance in situations such as job interviews. In modern times, however, we are also exposed to different types of stressors that may not be as immediate or short-term as the sorts of stressors our bodies were evolved to deal with, and these can lead to health problems in the long-term.
Types of stress
There are three different types of stress. First, routine stresses, which are the stressors that are present in everyday life (e.g. housework, family interactions, work-life). Second, major life stress, which is intense negative stressors (e.g. divorce, bereavement, job loss). Third, traumatic stress, which is a life-threatening stressor (e.g. war, natural disaster, assault).
For people that are exposed to high levels of any of these types of stress, the body’s stress response can lead to physical and/or mental diseases. With routine stress, your body can go into fight, flight, or freeze multiple times over the course of the day. Over time, this can increase blood pressure, due to the extra fats that were released lining the artery walls, a decreased immune system response, digestive problems, such as irritable bowel syndrome (IBS) and stomach ulcers, and anxiety problems.
There is a strong association between major life stressors and major depression. Psychologists have developed a questionnaire that looks at the number of major life events an individual has experienced, and a high score on this questionnaire is significantly related to the onset of major depression. These can include events such as divorce, bereavement, assault, serious illness or injury, and burglary. This relationship is mediated by the finding that people with depression often create stressful situations. and that there appears to be a genetic component, whereby people with certain personality characteristics are more likely to find themselves in stressful situations.
Post-traumatic stress disorder (PTSD) can be brought on by exposure to severe traumatic stress. People who develop PTSD after a traumatic event are unable to “switch off” their body’s stress response and this can lead to several symptoms:
- flashbacks of the event, including nightmares and intrusive images
- distress in response to triggers that remind them of the event
- fatigue from trying to repress memories of the event
- excessive rumination about unanswerable questions surrounding the event
- hyperarousal, including hypervigilance for threats, exaggerated startle response, irritability, difficulty concentrating, sleep problems
- emotional numbing – an inability to feel emotions, feeling detached from people and activities that used to bring pleasure
- amnesia about the event
- psychological problems including depression, anxiety, shame, and guilt
Thankfully, most people with PTSD do recover after a year, although they may need therapy to help them.
How can you reduce stress?
There are a number of techniques that can help to reduce the body’s stress response:
- Biofeedback is a method that uses visual or auditory feedback to gain control over bodily functions that are normally involuntary (e.g. heart rate, blood flow, and blood pressure) and is an effective method of stress reduction.
- Progressive muscle relaxation is a technique that involves isolating each muscle group and tensing it, followed by relaxing it. The muscle groups are moved through systematically until every muscle group has been tensed and relaxed.
- Mindfulness meditation involves deliberately noticing the body’s sensations as well as sensations that stem from the outside world. It creates awareness of the present moment and can help to reduce stress.
- Physical exercise involves engaging in regular moderate to intense physical exercise and helps improve mental wellbeing and reduce stress.
- Tai chi combines physical flowing movements and deep breathing and this can help reduce stress.
- Yoga is similar to tai chi in that it combines movement and deep breathing, but yoga also has a focus on flexibility and stretching. It is also effective at reducing stress.