While there had been significant steps in the understanding, awareness and treatment of depression, unlike most other medical illnesses, neuroscientists still don’t have a precise understanding of the exact causes of depression.
Rather, the causes of depression seem to be a complex interaction between a person’s genes, physiology, environment and their susceptibility to developing the disease, but there is no diagnostic tool that can accurately predict where or when it will occur.
Exposure to long term, chronic stress, as a result of highly stressful situations.
Depression has been labeled “the silent face of stress”.
While this complex interaction between genes, physiology and environment is a significant factor in the predisposition for the onset of depression in an individual, a precursor to the onset of depression, is almost always, long term, ongoing stressful life events – or chronic stress.
Generally, depression does not result from a single situation or incident, rather from a combination of recent events and other long term, personal factors.
We have previously examined the physiological changes that occur to our body when we are in a state of stress, where we are subject to elevated levels of the stress hormones, such as cortisol, that are released as part of our body’s fight or flight stress response.
When we suffer from chronic stress, and are unable to switch-off our body’s stress response, researchers believe that these elevated levels of cortisol, can impact the way our nerve cells communicate within our brain.
This results in a disruption with the way the mood regulating neurotransmitters function, which results in reduced levels of the “feel-good” neurotransmitter serotonin, and the “motivational” neurotransmitter dopamine.
It is the reduced levels of dopamine and serotonin in the body, which researchers believe is a contributing factor for people with clinical depression.
Serotonin is a neurotransmitters produced both in the brain and in the gut, which helps contribute to our wellbeing and happiness, and seems to help keep our moods under control by helping with sleep, calming anxiety, muscle relaxation and relieving depression.
The neurotransmitter dopamine, is generated within the brain and affects our emotions, movement and our sensations of pleasure and pain. It also is associated with motivation and reward, and helps us with our creativity and decision making.
Chronic Stress Damages and Shrinks Our Brain
One Danish research study, in an attempt to further explain how stress can cause depression, showed that stress reduced the ability for the brain to rebuild healthy brain tissue, and so regenerate and keep itself healthy.
This study used rats because they could document that rats react to stress in the same way that we humans do.
The researchers found that after exposure to stress, the subjects brain (specifically the hippocampus) shrunk in size, impacting both short term memory and learning abilities. Comparing the brains of stressed rats and healthy rats, the researchers found that the stressed subjects produced 20 % fewer new brain cells, than the healthy subjects.
Indirect factors associated with chronic stress
We’ve looked at some of the direct physiological causal/risk factors associated with stress, however changes to our normal, healthy lifestyle behaviors and patterns – also have a very significant effect.
Very often, the stress that we are under causes us to make lifestyle changes and neglect the healthy practices that we previously used to defend ourselves against the physiological effects of stress. It is these changes – the lowering of our defensive mechanisms – that can accelerate the onset of depression.
Understanding these factors and recognizing that we are at risk, is an important defensive mechanism in helping to defend ourselves and prevent depression during extended periods of high stress.
Stress impacts our normal, healthy coping strategies
Stress impacts our normal, healthy coping strategies as we often change or stop, many of the healthy habits that help us defend against stress.
For example, stress at work, means longer hours, which means we skip our regular exercise, we don’t have time to sit and relax with a book, we don’t get enough sleep, or find time to catch up with friends – all of which helps keep our mood on track.
Initial stress, generates further stress
So we’re feeling tired, flat and lacking concentration at work, and we make mistakes, or let loose with an angry or irritable outburst, causing problems with our boss, colleagues or clients – all of which increases the stress that we are under.
When we’re under stress, we often become irritable and withdraw from our friends, family, partner or spouse, which creates communication problems and relationship stress, which further adds to our overall chronic stress load.
Unhealthy coping behavior
Not only do we cut back on our healthy coping behavior when we’re under stress, but we often go in the opposite direction, by increasing unhealthy behavior, with things that exacerbate the stress and health problems, such as increasing our alcohol intake, or eating badly – with more high fat, high carbohydrate and high sugar foods and snacks, both of which significant increase the damage to our body..
Scientists have determined that across all depression, approximately 50% of the cause is genetic, where there is an increased risk of developing depression, if one of your parent has been diagnosed with depression.
Although, in most cases, depression is unlikely to occur without stressful life events and other psychological or physical factors.
When it comes to major/clinical depression, when a person has a parent or sibling with major depression, that person probably has a 2 or 3 times (20-30%) greater risk of developing depression compared with the average person (approx. 10%).
It’s not that someone simply “inherits” depression from their mother or father, rather, we all inherit a unique combination of genes from our parents, and certain genetic combinations can predispose us to a particular illness.
Stress-prone personality types
It has also been shown that there are certain personality types that are more at risk of developing depression that others.
Those with the competitive, time-urgent, aggressive and impatient Type A personalities, are much more stress prone than others.
In addition, those people with a codependent personality – the perfectionist, super-overachievers, who take on all tasks as crisis managers, are much more likely to suffer the effects of chronic stress.
The helpless-hopeless personality types are also stress prone, with traits associated with those of someone with low self-esteem, with poor self-motivation, emotional dysfunction, high perceptions and expectations of failure and feelings of frustration, despair or futility.
Chronic illness and pain can cause significant disruption in our lives and lifestyle.
This chronic illness can limit our mobility and independence, and force us to adjust our future plans, lifestyle and employment, impacting our self-confidence and often making it impossible to continue with the activities that we enjoy.
The grief and resulting stress, can easily become chronic, and for many patients, develop further into depression or anxiety.
As a result, depression is one of the most common complications of chronic illnesses, where it is estimated that between 25% and 33% of patients with a serious medical illness or injury, experience symptoms of depression.
The research on chronic illnesses and depression indicates patients with chronic illnesses experience depression at the following rates:
- Heart attack: 40% – 65% experience depression
- Coronary artery disease (without heart attack): 18% – 20
- Parkinson’s disease: 40%
- Multiple sclerosis: 40%
- Stroke: 10% – 27%
- Cancer: 25%
- Diabetes: 25%
- Chronic pain syndrome: 30% – 54%
How is depression different to anxiety?
While anxiety and depression are different conditions, and they have their own causes and emotional and behavioral symptoms, they also share some of the same causes and symptoms.
It’s also common for someone to suffer both anxiety and depression at the same time – with more than 50% of those with depression, also experiencing symptoms of anxiety. There is also a causal relationship between anxiety and depression, where the onset of anxiety, can lead to the development of depression. In fact, having an anxiety disorder, is the most significant single predictor of a person suffering depression.
Current research suggests that anxiety treatment should begin with first treating the depression, as the symptoms of depression can trigger anxiety. So reducing the symptoms of depression, will often lead to reduced feelings of anxiety,
The Stress => Anxiety => Depression cycle
While not a fixed rule, you can think of the relationship between the three elements as a cycle:
stress can lead to anxiety => anxiety can lead to depression
where, if you are unable to manage and dissolve the feelings of stress that you feel, then you can find yourself living in worry of the stress returning.
You may then find that these feelings of worry, can become a persistent anxiety and this long term anxiety, can then develop further into depression.
Depression and suicide risk
One of the symptoms of depression is a sense of hopelessness and worthlessness and a feeling that nothing will ever get better and nothing will ever improve.
Depression carries a high risk of suicide and people with depression commonly have these thoughts.
Anyone who has expressed these or similar thoughts, must be taken seriously and help must be immediately sought, through national support hotlines and local medical professionals and support groups who are set-up to advise both the person suffering and concerned family and friends.