In spite of depression being a mental illness that will affect more than 10% of the population at some point in their lives, the main causes of depression are yet to be pinpointed. Physical and psychological factors appear to cause depression in adults, teens and children. Genetics are also believed to be involved, as depression often runs in families. However, the specific genes that cause depression have not yet been found. It is likely factors combine in many ways to create the actual cause of depression in any given person.
Biological Causes of Depression
There are several biological factors believed to contribute to depression but their exact mechanisms are unclear. In spite of years of research, we only understand that biological differences exist in people with depression, and not how the differences cause depression, specifically. These biological causes of depression are thought to be present in teens and children as well.
The biological factors that contribute to depression include:1
- Physical changes to the brain – it is known that some part of a depressed brain show less activity than normal when stimulated; some parts of the brain even reduce in volume.
- Neurotransmitters – these chemical messengers in the brain have been implicated in the cause of depression since the 1970s. A central nervous system disruption in serotonin, norepinephrine and dopamine are thought to be a direct cause of depression.
- Hormones – hormone changes may trigger depression. Hormone changes are seen in thyroid problems, menopause and in other conditions.
Environmental Causes of Depression
While no single life event is thought to cause depression, stressful events can trigger, or worsen, depression. Some research has shown those with a specific genetic abnormality are at greater risk of depression during stressful life events.2 Early childhood trauma is suggested as a cause of depression in children, teens and adults.
Other environmental factors contributing to depression include:
- Death of a loved one
- Loss of a job
- Financial troubles
- High stress situations
One of the causes of teen depression is thought to be a learned feeling of helplessness. Some teens with depression appear to feel like they cannot find answers to life's problems.
Causes of Depression in Women vs. Causes of Depression in Men
Causes of depression in women and men include all of the above, but there are certain risks more common to each gender. An environmental cause of depression in men is more likely to be job-related while an environmental cause of depression in women is more likely to involve their social relationships. Other causes of depression that appear to be gender-related include:
- Pregnancy – up to 15% of women experience postpartum depression. Some men also show postnatal depression (read about: Postpartum Depression in Men).
- Menopause – the changes in hormones are thought to be a cause of depression in women.
- Low testosterone levels – men with lower testosterone levels later in life have a greater chance of developing depression.