What causes depression?

The human brain is like its own tiny universe, and it contains roughly 100 billion neurons (which is the same number of galaxies in our own universe). This can make it hard for researchers to pinpoint the exact cause of mental health problems. Depression is a good example, because there are still so many unanswered questions about how it works or where it comes from.

But there is good news. Research on depression is ongoing, so there are bound to be many discoveries in the near future. Also, even though we aren’t sure about an exact cause, we do have an idea of what factors contribute to a person experiencing depression. There are several possible things that can cause depression, and experts believe they usually work together.

Genetic factors

Depression seems to be more common among people whose relatives also have depression. Because of this, experts think that there is probably a genetic aspect to depression. Perhaps there are genes that make people predisposed to negative moods, or make them react to drug therapy a certain way. These genes could then be passed down through families.

Biological factors

There are some pronounced physical differences between a depressed brain and a non-depressed brain. For example, the hippocampus – a part of the brain that helps with memory, learning, and emotion – is often smaller among people with depression, compared to people who do not have depression. The frontal lobe, which controls things like memory, language, judgement, and emotional expression, also tends to be smaller among people with depression.

While researchers are still studying the biological differences in depressed brains, so far evidence suggests that there definitely are some concrete differences.

Biochemical factors

You’ve probably heard that depression is caused by a chemical imbalance. Things are a little more complicated than that, but chemicals definitely play a role in depression. People with depression often have an imbalance in their brain chemistry, particularly with their serotonin and dopamine (also called the “happy” chemicals). This can lead to problems with memory, irritability, and mood regulation. Many people take medications to regulate the chemical balance of their brain.

Hormonal factors

Things like pregnancy, thyroid problems, and menopause can throw people’s hormones off balance. This can, in turn, trigger episodes of depression. An example of this is postpartum depression after childbirth, which affects nearly one in seven new mothers.

Situational and seasonal factors

People can become depressed if there are triggers in their lives. Triggers can be situational – for example, a stressful life event like divorce, the death of a loved one, or a difficult and strenuous job. Some people experience post-traumatic stress disorder (PTSD), which is a mental health disorder caused by trauma.

Depression can be triggered by medical problems like a chronic illness, an undiagnosed illness, or something that threatens a person’s life. Many people experience seasonal affective disorder (SAD), a form of depression that happens as the daylight hours start getting shorter in the fall and into the winter.

What can you do?

Depression is a complex disorder with a lot of variables, and there’s no one size fits all approach to the experience, diagnosis, or treatment of depression. It’s helpful to be aware of the signs of depression, and you also shouldn’t wait to seek help if you or someone you know needs support. If you think you might be experiencing depression of any kind, talk to your primary care provider about how you’re feeling. They’ll ask questions, make an assessment, and refer you to a professional who is equipped to help.

Read more
  • T Frodl, A Schaub, S Banac, M Charypar, M Jäger, P Kümmler, R Bottlender, T Zetzsche, et al. “Reduced hippocampal volume correlates with executive dysfunctioning in major depression.” J Psychiatry Neurosci. 31(5): 316–325. Web. Sep 2006.  
  • Melinda Smith and Jeanne Segal.  “Depression Symptoms and Warning Signs.” HelpGuide. Helpguide.org, Sep 2016. Web.
  • “What causes depression?” Health.harvard.edu. Harvard University, June 2009. Web.
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