Stress and the nervous system

Depression, anxiety and stress can manifest in the individual in a variety of ways: physical, emotional, cognitive and behavioural. These mental health conditions are however, all characterised by imbalances in the autonomic nervous system, most commonly over-activation of the sympathetic branch of the nervous system.

The sympathetic branch of the nervous system is responsible for producing our “stress response”. This mechanism (also known as the “fight or flight” response) has evolved over thousands of years to help us survive a short-term, life-threatening, physical crisis such as fighting off an attacker or running to save our life.

The “stress response” produces a physiological and psychological state of hyperarousal, characterised by increases in: heart rate, blood pressure, muscle tension and startle reflex, along with rapid, shallow breathing and strong emotions such as anger, fear, panic and anxiety. These changes are necessary to prepare the body and mind for action. Once the threat has passed a healthy nervous system will activate the parasympathetic branch of the nervous system to produce the “relaxation response” which returns us to a state of “homeostasis” or internal equilibrium.

Being able to switch easily between sympathetic and parasympathetic activation at a moment’s notice is a sign of healthy nervous system.

Whilst the “stress response” served our ancestors well, it is less useful in our modern world which rarely presents us with tangible physical threats from which we need to run away or defend ourselves. Instead our modern stressors are intangible psychological ones. Endless worry and anxiety about work, money, responsibilities and relationships produces the same physiological responses that we would experience if we were being confronted by an attacker.

When activated chronically (frequently or long term) this “stress response” can have serious consequences for our physical and mental health, impacting every system of the body and affecting the functioning of the brain.