This article was taken from: https://www.theguardian.com/society/2019/oct/13/the-link-between-stress-and-depression-and-the-10-simple-words-that-could-help
By Dean Burnett Guardian news
Neurological insights into how the brain processes stress, and how it can develop into depression, have led to new interventions
It’s a damp, midweek afternoon. Even so, Cardiff’s walk-in stress management course has pulled in more than 50 people. There are teenagers, white-haired older people with walking aids, people from Caucasian, Asian and Middle Eastern backgrounds. There is at least one pair who look like a parent and child – I’m unsure who is there to support whom.
The course instructor makes it clear that she is not going to ask people to speak out about their own stress levels in this first class: “We know speaking in public is stressful in itself.” She tells us a bit about previous attendees: a police officer whose inexplicable and constant worrying prevented him from functioning; a retired 71-year-old unable to shake the incomprehensible but constant fatigue and sadness that blighted his life; a single mother unable to attend her daughter’s school concert, despite the disappointment it would cause.
What is the common theme that links these people – and the varied group sitting there this afternoon and listening?
Stress may once just have been a kind of executive trophy – “I’m so stressed!” – but recent research suggests it is a key element in developing mental health problems such as depression and anxiety.
The constant, stress-induced stimulation of key brain regions seems to be a major contributor to anxiety. And, in turn, vital brain regions becoming unresponsive and inflexible is believed to be a fundamental element of depressive disorders. Why do these regions become unresponsive? Possibly because they’re overworked, exhausted, by the effects of stress. This would explain why anxiety and depression regularly occur together.
So what is stress? In essence, it is the first stage of the fight-or-flight response, the classic reaction to danger, the ingrained reflex that compels you to tackle danger head-on or run screaming from it. A third option, freeze, is also included in the modern-day understanding, which explains that inability to move when you’re truly scared.
This potent fear response isn’t like a switch, a simple yes/no thing. There are neurological and biochemical systems that prepare your brain, and body, for having to deal with a threat. It’s regulated by a complex suite of brain networks and hormonal reactions, and one key element in the stress response is the amygdala, the part of the brain that (among other things) decides whether or not stress is warranted.
The stress response has numerous potent effects on us. It increases our focus on negative things, such as whatever is causing the stress, because when you’re dealing with a problem you can’t afford to waste time pondering irrelevant things. It puts your brain and body into a more alert state, meaning you become more sensitive to hazards and risks, both physically and mentally. It’s useful for keeping you safe, but again leads to you focusing on the negatives, the unpleasant aspects of your current existence, and downplays the potentially distracting positives.
Problematically, because of these things, stress is also very stimulating. It releases several potent chemicals into your bloodstream – cortisol for instance, which amps up your heart rate, muscle tension, glucose uptake, even your immune system responses.
The trigger, the activation of the stress response, comes from our brains, with the hypothalamic-pituitary-adrenal (HPA) axis – a complex association between the hypothalamus and the pituitary and adrenal glands – as the key element. The HPA axis is basically the link between the brain and the body when it comes to stress. When our brain decides that stress is required, signals are sent to the HPA axis, which in turn releases a complex sequence of chemicals that ends up with stress hormones, such as cortisol and glucocorticoids, being released into our bloodstream.
But here’s the problem. In many people, this ability of the HPA axis to recognise when there’s enough stress chemical in the body and so cease production is disrupted in some way. The HPA axis can start the physical stress response but doesn’t seem to know when to stop.
This might sound like a mild annoyance but there’s mounting evidence to suggest that it’s a cause of multiple mental health problems, particularly depression. Those who have chronic depression, and many who have killed themselves, have been shown to have significantly elevated levels of glucocorticoids, cortisol and other stress chemicals in their blood and tissues.
The constant bombardment from stress chemicals potentially underlies many of the physical symptoms of depression. Weight gain, hypertension, a suppressed immune system, heart problems – all can be attributed to the persistent action of stress chemicals in the body. For example, these stress chemicals and hormones seem to have a potent effect on neurons, and therefore the functioning of the brain. Specifically, they seem to stimulate areas such as the hippocampus and prefrontal cortex to enhance our memory, thinking and focus, because when you’re in a stressful situation, you need to have your wits about you, and you need to remember what happens in case it happens again.
Unfortunately, this causes a problem. Neurons can handle a certain amount of increased signalling, some excitation. But too much leads to excitotoxicity, a phenomenon whereby too much activity damages and impairs the neuron. The complex biochemical processes a neuron engages in are quite demanding. Give them time to restock and replenish after being pushed to their limit and they’ll be fine. But keep pushing them and they’ll suffer.
So, stress chemicals stimulate many areas of the brain. But when the HPA axis keeps pumping them out, those brain areas are stimulated too much, exhausting and damaging the neurons, causing them to lose plasticity. And a loss of neuroplasticity is now believed by some scientists to be a key part of depression. Simultaneously, there’s no reason why other parts of the brain, with neurons that have subtly different properties, can’t respond differently to the stress hormones, possibly being enhanced by them.
There is a possibility that it’s the unhampered stress response that causes some or even all of the issues of depression, inducing the physical symptoms, reducing neuroplasticity in certain key areas by overworking them while enhancing other regions to the extent that they become dominant to a disruptive extent.