The cause of depression is no one, single thing; rather, it’s a combination of various possible factors. But the precise combination is unique to each person living with depression. Learning what these possible factors are may help you to better understand how your experience with depression developed.
Researchers have identified a complex interplay between biological, psychological, environmental, and social factors that can contribute to the development of depression.
Causes of depression
Depression often arises from a combination of genetic, biological, environmental, and psychological causes that combine to . Imagine depression as a tangled web: each strand represents a potential contributing factor, and no two webs look exactly the same.
Genetic factors: Research shows that a family history of depression increases a your chances of developing the condition yourself. This suggests a genetic element to depression, however, there is no single ‘depression gene.’ It’s more likely that many tiny quirks across many genes contribute to increased risk of depression, but a precise genetic pattern is unknown.
However, even this alone is not enough to cause depression. A family history doesn’t guarantee you’ll develop depression, and conversely, someone without a family history can still develop it.
Brain chemical factors: Neurotransmitters are chemical messengers that are constantly coming and going between brain cells in incredibly intricate patterns order to regulate mood, sleep, appetite, and more. Imbalances in several neurotransmitters like serotonin and dopamine are thought to play a role in depression. But again, the exact definition of this ‘imbalance’ is not known, nor is an ‘ideal,’ non-depressive balance defined.
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In recent years, media reports have led to the widespread belief that depression is caused by low serotonin levels. This is an oversimplification of a very complex theory. While altered serotonin levels likely contribute to depression, there are many other neurotransmitters — and other factors — involved.
Life events: Distressing life experiences like the death of a loved one, job loss, relationship problems, or trauma can trigger depression. These events deplete emotional reserves and make it harder to cope with daily challenges.
Imagine daily life as carrying a heavy backpack –- distressing events like these add more weight, making it increasingly difficult to move forward. Over time, these depleted emotional reserves and constant coping can change the way the brain functions, contributing to depression.
Chronic illness: Similarly, living with a chronic health condition, like diabetes, chronic pain, or an autoimmune disease, can contribute to depression or worsen its symptoms. The physical limitations, unpredictability, and emotional strain of managing a chronic illness can create a vicious cycle of negative thoughts and feelings.
Again, over time, these negative thoughts can become a pattern that changes the way the brain functions, contributing to depression.
Personality traits: People with low self-esteem, a tendency toward pessimism, or a tendency to self-criticise may be more susceptible to depression. These traits can make it more difficult to bounce back from setbacks and instead, fuel negative thought patterns.
Think of a negative thought pattern as a worn path in the forest –- the more you walk it, the easier and more familiar it becomes. Again, over time, this can change the way the brain functions by becoming the default pattern the brain follows, thus contributing to depression.
Social factors: Social isolation, a lack of social support, and/or societal discrimination can contribute to depression. Humans are social creatures who require strong social connections in order to thrive.
Imagine a plant – without sunlight and water, it withers. For humans, social connections are our sunlight and water. Without connection, support, and acceptance from others, we wither, too.
Each of these factors interact in a unique way and have a cumulative effect. For example, someone with a family history of depression might be more vulnerable to developing the condition after a distressing experience.
Debunking serotonin as the cause of depression
One of the most pervasive myths about the cause of depression is the notion that it is solely caused by low serotonin levels in the brain. Serotonin is a neurotransmitter that helps regulate brain systems that control everything from body temperature to sex drive, mood to hunger, and more.
While serotonin does play a role in regulating mood — and therefore may play a role in causing the development of depression — the relationship between serotonin levels and depression is much more complex than commonly portrayed. Depression likely involves imbalances in multiple neurotransmitters, not just serotonin.
Research has shown that while some people with depression may have lower levels of serotonin, many others do not show such imbalance. Moreover, artificially increasing serotonin levels through medications like selective serotonin reuptake inhibitors (SSRIs), while helpful for many, does not always ease symptoms for everyone. (Additionally, SSRIs and other antidepressants don’t ‘replace’ missing serotonin; they influence how the brain uses and controls it.)
Again, all of this suggests that a serotonin imbalance is not the sole cause of depression, but one of many, many potential factors.
Why the complexity of depression matters
Depression is a very personal condition. No two people will experience the same depression symptoms, nor experience them in the same way. That’s because the causes of depression are unique to each person, too. Personalised treatment approaches that address the unique factors contributing to each person’s depression are the most successful.
Therapy — whether one-on-one sessions or personalised digital programs like Mitsu’s — along with medication, lifestyle changes, and social support may all play integral roles in managing depression effectively.
By acknowledging the diverse causes of depression, we can foster a more compassionate and informed approach to mental healthcare — and to each other.
If you or a loved one are experiencing depression, remember: depression doesn’t define you, and with the right support and resources, you can find your way back to a brighter place.
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SOURCES:
- Jauhar S, Cowen PJ, Browning M. Fifty years on: Serotonin and depression. J Psychopharmacol. 2023 Mar;37(3):237-241.
- Moncrieff, J., Cooper, R.E., Stockmann, T. et al. The serotonin theory of depression: a systematic umbrella review of the evidence. Mol Psychiatry. 28, 3243–3256 (2023).
- Remes O, Mendes JF, Templeton P. Biological, Psychological, and Social Determinants of Depression: A Review of Recent Literature. Brain Sci. 2021 Dec 10;11(12):1633.
