Depression is a complex disorder that addresses a large umbrella of different expressions. Despite ongoing research, we are only just scraping the surface of understanding how depression is caused within our brains. However, we do have plenty of good information to point us in the right direction. Just keep in mind that for most people, there won’t be a single cause for their depression, but a combination of the different causes below.


Research suggests that our DNA may set us up to be more or less likely to develop depression in our lives. This predisposition is based in the combination of many different genes, so there is no test to see whether you have this predisposition (yet!)

Based on twin studies, scientists believe that about 30% of the cause of depression may be down to our genetics, with other factors making up the other 70%. This means that while genetics can determine a lot, our genes alone cannot set our destiny in concrete. It is very uncommon for this genetic predisposition to cause depression without other contributing factors.

The risk of developing depression is also thought to be passed on from our biological parents. In children with parents who have been diagnosed with clinical depression, the risk of being diagnosed within their life is at 40% – with other factors still playing a role. One positive side of this genetic cause is that people with depression are likely to have relatives who have been through similar experiences, who may be able to play a supportive role in their life.

Brain chemistry

Our brains are fantastically intricate systems that regulate every aspect of our experience, including our emotions. However, when these systems are disrupted from functioning normally, this can start to cause problems.

In the case of depression, it is theorized that the problem sits with our neurotransmitters – chemicals in the brain that carry signals between the nerve cells. When a person is depressed, these signals become weaker or disrupted as they are passed along, whereas a healthy brain will be able to pass the message along at full strength.

What causes these changes in brain chemistry remains under investigation. The main schools of thought suggest that people may experience these changes due to biological differences at birth, the effects of long-term stress, some medical conditions that alter brain function, or the use of certain substances (including medication side effects).


For a long time, it was thought that if a person was depressed, there must be something fundamentally wrong with them (such as the aforementioned genetic or biochemical issues) in order for it to be counted as a “real” mental health issue. On the contrary, it is now believed by many researchers that stressful circumstances are one of the most common contributors to developing depression.
The types of stresses that can cause depression are many and varied. Most obviously, people who have experienced extended periods of stress such as long-term unemployment, ongoing loneliness or living in an abusive relationship are at high risk.

Apart from these long-term issues, life changing events such as the death of a loved one, an important relationship breakup, or experiencing an unexpected trauma can act as triggering events. Even seemingly positive events such as a marriage, moving house, or getting a new job can sometimes act as the impetus for depression to take hold, especially if the person has an existing predisposition.
With this in mind, we have to remember that having a normal reaction to a stressful situation should not be interpreted as depression. It’s okay to feel bad when bad things happen to us, but if these feelings become intense and ongoing and we can’t bounce back, that becomes an issue.

Marginalising factors

Research over decades has shown that people belonging to marginalized groups are at much greater risk of depression. Such groups include refugees and immigrants, people of color, the LGBTQI+ community, and chronically ill or disabled people.

It must be noted that this higher risk of developing depression is not inherently caused by belonging to one of these groups, it is the actions of the oppressive society around them that causes long term stress and damage to their self-esteem – raising the risk of depression dramatically.

When going through life facing obstacles that others will never experience, and being passed over for certain opportunities, it is easy to develop a sense of hopelessness and despair. At the same time, conspicuous bullying and discrimination from others can be internalized over one’s life, leaving a person feeling worthless and unlovable, and exacerbating any other issues that are occurring in their life.


The way our brains filter the information that we receive on a daily basis forms the bedrock of our personality. It also defines the way we see the world. Is it threatening or safe? Is it mostly positive or mostly negative? Is it easier to have hope or to expect the worst? Our personality traits can have a big impact on how likely we are to develop depression. Unsurprisingly, the people at highest risk are those who have low self-esteem, are highly critical, negative, sensitive to criticism or socially avoidant.

Of course, having one of these traits doesn’t have to mean you have (or will develop) depression! It just means that you might be more susceptible to it.

Putting it all together

As research into the causes of depression continues, we are slowly putting together the pieces of the puzzle. However, it seems unlikely that we will ever be able to take a test to determine the causes of our depression, because it’s most likely to be a combination of multiple complex factors. At the end of the day, what we can say for certain is that depression is a real health issue, and is definitely not caused by any personal choice, failing or weakness!

This piece was written by one of the ICLA eFriend Peer Support Workers. eFriend is an online platform where you can connect with a trained peer support worker whom has their own lived experience of feeling lonely, isolated, stressed or worried. You can speak to your eFriend Peer via video or phone call. Your eFriend Peer will listen, validate and provide hope. If you like, they can also assist you to identify any other services you may like to try or help you create plans to improve your personal well-being. Or they can simply listen.

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