In short, STRESS CAUSES OVER-BREATHING. More specifically, we become conditioned to respond to stress by over-breathing or mouth breathing as an emergency response.
Our innate response to stress is the ‘fight or flight’ state which is an evolutionary response to a perceived threat, and served to effect changes in our bodies that prioritise or make us more capable of ‘fighting’ or ‘fleeing’. For example, if a wild animal poses a threat to our safety, we choose to either fight or flee the source of this extreme stress. In this evolutionary example, the stressor either goes away either by us successfully fighting or fleeing the animal. Or we die. There was indeed an “emergency” that asked for a body/mind response that called upon all of our resources. With the removal of the stress, our physiology returns back to a basal level and we return to the tasks of living.
The modern stressors we deal with are, more often than not, far less threatening to our safety. Whilst they are often less severe, they are far more chronic or long lasting. Unfortunately we do not often return to this basal low level (or zero level) of stress we predominantly existed in (outside of emergencies) in times past. As a result we reduce our body’s ability to deal with more acute stressors and we often regularly respond in ‘emergency’ fashion to stressors that do not require this response.
Nevertheless, the process of evolution has led to us responding to any stress in a way that has long been our mode of functioning. That the severity and types of stress we now deal with are vastly different to those we evolved dealing with is not of consequence to the body. Our safety is far more assured than in previous times, yet our body still responds with this ‘fight or flight’ mechanism.
Our body’s innate stress response is driven by the ‘autonomic nervous system’ (ANS) – a part of our nervous system that controls the functions of our organs and many of our body’s functions (including respiration!!) which functions regardless of whether we are conscious of it or not; i.e. the functions it controls still operate whether we are awake or asleep. It comprises the sympathetic nervous system (SNS), which excites or arouses the body to prepare for the ‘fight or flight’ stress response, and the parasympathetic nervous system (PSNS), which calms the mind and rejuvenates the body. The sympathetic and parasympathetic divisions typically function in complementary opposition to each other.
A common analogy used to compare these two facets of the autonomic nervous system describes the SNS as the ‘accelerator’ and the PSNS as the ‘brake’. The sympathetic division typically functions in actions requiring quick responses. The parasympathetic division functions with actions that do not require immediate reaction.
The ‘fight or flight’ response to stress causes the sympathetic nervous system to dominate. Sympathetic nervous system dominance leads to the following changes characteristic of the ‘fight or flight’ response:
- Adrenaline levels in the blood rise.
- Over time, blood levels of cortisol increase.
- Heart rate increases
- Blood pressure increases
- Blood is redirected from the digestive system to skeletal muscles
- Breathing rate and volume increases
- Triggers the burning of sugar and storage of fat.
- Elevation of plasma levels of clotting factors and histamine.
When breathing rate and volume rise we over breathe. When we over breathe we lose too much CO2 and the blood becomes too alkaline. As a result, haemoglobin holds on to inhaled oxygen in the blood stream, cells become deprived of oxygen and we experience different symptoms.
Once this response occurs regularly enough it becomes a conditioned response or a habit. Over time, this adaptive response, originally designed as an emergency response to an acute stress, becomes our normal mode of functioning.
But, as humans we are born ‘obligate nose breathers’ meaning that we do not possess the voluntary ability to breathe through our mouths. Mouth-breathing, the most common example of over-breathing is a learned response triggered by our emergency response to stress.
For example, you will notice that newborn infants breathe quietly through their nose all of the time. However, if their nose becomes blocked they will struggle to get air into their lungs. As they have not learned the response to mouth breathe, they will begin to suffocate. As a response, they begin to cry which allows large volumes of air to enter the lungs rectifying the emergency. The infant then returns to its normal nose breathing.
When subsequent stressors arise they repeat this emergency response, until they become conditioned from a very early age to respond to any sign of stress with this emergency mouth breathing response.
In our modern world of chronic low level stress, mouth-breathing, originally an emergency response, becomes a conditioned response and a habit. And, eventually our normal way of functioning.
The parasympathetic nervous system, on the other hand, promotes a “rest and digest” response, thus a calming of the nerves return to regular function, and enhance digestion. Some of the functions of the PSNS are:
- Increase in digestive system function.
- Breathing rate and volume decrease
- Lowering of the heart rate (or returning it back to normal or resting rates)
- Lowered blood pressure
- Reduced blood cortisol
- Constriction of the pupil and contraction of the ciliary muscle to the lens, allowing for closer vision.
- Stimulation salivary gland of secretion, and accelerates peristalsis, so, in keeping with the rest and digest functions, appropriate PNS activity mediates digestion of food and indirectly, the absorption of nutrients
- Increase in blood flow to the brain
- Increase in ‘happy’ neurotransmitters, serotonin and dopamine – low levels of these are seen in depression
- Is also involved in erection of genitals
- Stimulates sexual arousal
- Increase in night time melotonin – promoting a more restful sleep.