THUNAIAt some point, nearly everyone encounters stressful life events: the death of a loved one, the loss of a job, an illness, or a relationship spiralling downward. Some must cope with the early loss of a parent, domestic violence, or sexual abuse. While not everyone who faces these stresses develops a mood disorder — in fact, many do not — stress plays an important role in depression.
Your genetic makeup influences how sensitive you are to stressful life events. When genetics, biology, and stressful life situations come together, depression can often result.
Stress has its own physiological consequences. It triggers a chain of chemical reactions and responses in the body. If the stress is short-lived, the body usually returns to normal. But when stress is chronic or the system gets stuck in overdrive, changes in the body and brain can be long-lasting.
How stress affects the body – HPA system:
Stress can be defined as an automatic physical response to any stimulus that requires you to adjust to change. Every real or perceived threat to your body triggers a cascade of stress hormones that produces physiological changes. We all know the sensations: your heart pounds, muscles tense, breathing quickens, and beads of sweat appear. This is known as the stress response.
The stress response starts with a signal from the part of your brain known as the hypothalamus. The hypothalamus joins the pituitary gland and the adrenal glands to form a trio known as the hypothalamic-pituitary-adrenal (HPA) axis, which governs a multitude of hormonal activities in the body and may play a role in depression as well.
When a physical or emotional threat looms, the hypothalamus secretes a hormone (CRH), which has the job of rousing your body. Hormones are complex chemicals that carry messages to organs or groups of cells throughout the body and trigger certain responses. CRH follows a pathway to your pituitary gland, where it stimulates the secretion of another hormone (ACTH), which pulses into your bloodstream. When ACTH reaches your adrenal glands, it prompts the release of cortisol.
The boost in cortisol readies your body to fight or flee. Your heart beats faster — up to five times as quickly as normal — and your blood pressure rises. Your breath quickens as your body takes in extra oxygen. Sharpened senses, such as sight and hearing, make you more alert.
CRH also affects the cerebral cortex, part of the amygdala, and the brainstem. It is thought to play a major role in coordinating your thoughts and behaviors, emotional reactions, and involuntary responses. Working along a variety of neural pathways, it influences the concentration of neurotransmitters throughout the brain. Disturbances in hormonal systems, therefore, may well affect neurotransmitters, and vice versa.
Normally, a feedback loop allows the body to turn off "fight-or-flight" defenses when the threat passes. In some cases, though, the floodgates never close properly, and cortisol levels rise too often or simply stay high. This can contribute to problems such as high blood pressure, immune suppression, asthma, and possibly depression.
Studies have shown that people who are depressed or have dysthymia typically have increased levels of CRH. Antidepressants and electroconvulsive therapy are both known to reduce these high CRH levels. As CRH levels return to normal, depressive symptoms recede. Research also suggests that trauma during childhood can negatively affect the functioning of CRH and the HPA axis throughout life.The survivors of abuse have a hyper vigilant emotional state as a result.
There are other pathways through which stress has an impact on our mental and physical health - through our nervous system, immune system etc.
Working with vagus nerve activation exercises can modulate the HPA stress response and calm our nervous system.
Please see these articles for more detailed information Huff Post ; Mayo Clinic