Depression does not have a single cause. Instead, it develops through a complex interaction of biological, psychological, and environmental factors. Updated for 2026, this article explains what researchers and clinicians understand about why depression happens — and why it affects people differently.
This article was reviewed and updated for 2026 to reflect current clinical understanding.
Depression Is Not “Just Being Sad”
Clinical depression, also known as major depressive disorder, is a recognized mental health condition with measurable effects on brain function and emotional regulation. It is not a personal weakness or a temporary emotional state. Learn more from the NHS.
Key Factors That Contribute to Depression
1. Genetics
Family history plays a significant role in depression risk. Research suggests that having a close relative with depression can substantially increase susceptibility, particularly when combined with environmental stressors.
Further reading on genetics and depression.
2. Brain Chemistry and Hormones
Neurotransmitters such as serotonin and dopamine influence mood regulation. Disruptions in these systems — sometimes triggered by hormonal changes, childbirth, or menopause — can increase vulnerability to depression.
Learn about the biochemistry of depression.
3. Stress and Trauma
Ongoing stress or traumatic experiences can overwhelm the brain’s coping mechanisms, increasing the likelihood of depressive episodes. Chronic stress often acts as a trigger rather than a single cause.
Stress and depression explained.
4. Lifestyle and Environment
Sleep deprivation, poor nutrition, isolation, financial strain, and seasonal changes can all influence mental health. While no single factor causes depression alone, combined pressures can significantly increase risk.
Environmental factors and depression.
5. Medical Conditions
Chronic illness, persistent pain, and neurological injuries are strongly associated with depression. Physical and mental health are deeply interconnected.
Chronic illness and mental health.
How Depression Affects the Brain
Brain imaging studies suggest that depression may involve changes in areas responsible for memory, emotional regulation, and decision-making, including the hippocampus and prefrontal cortex.
How depression can affect brain structure.
Understanding Causes Is the First Step Toward Support
While identifying the exact cause of depression is not always possible, understanding contributing factors can guide effective treatment and support strategies.
If you’re exploring professional support, our counsellors provide evidence-based depression therapy in Calgary and online counselling options.
For a broader overview, you may also find this helpful: Depression: What You Need to Know.
Frequently Asked Questions
Is depression caused by brain chemistry alone?
No. Depression usually results from a combination of biological, psychological, and environmental factors.
Can stress cause depression?
Chronic or overwhelming stress can increase the risk of depression, especially when combined with other vulnerabilities.
Does understanding the cause help with treatment?
Yes. Identifying contributing factors can help guide more effective and individualized treatment approaches.