Depression has a strong genetic component, but genes aren’t the only factor. Individual life experiences and your environment also play a part. The connection between these three factors may be the key.

Experts have not yet established a single cause of depression. It’s believed that it’s due to a combination of factors — one of them is your genes.

Research suggests depression may be associated with multiple genes but not caused by any one of them.

For example, a 2011 study found that chromosome 3p25-26 was prevalent in more than 800 families that had multiple members with depression. A study from 2021 found that 178 gene variants were associated with the onset of depression.

A 2022 research review also identified at least 7 genes linked to the presence of depression symptoms.

However, even if research has pointed to the prevalence of some genes or genetic variants among people with depression, it’s not clear what role they play in the development of depression.

In fact, researchers have yet to determine which specific gene, if any, causes depression. Also, genetics don’t seem to be the only factor associated with depression.

For one, not everyone who has depression has had a family history of the condition. Also, many people with close relatives living with depression never develop it.

The above may suggest depression is not hereditary but that some people with certain genes may be more likely to develop it in certain conditions, particularly when exposed to the same environment and experiences. That’s why depression can run in families, and experts continue looking into the genetic basis of depression.

In other words, researchers have found that the interaction of genes and environmental factors — including personal experiences — is key to the development of depression, as opposed to genes only.

Read more about the causes of depression.

In addition to genetics, adverse experiences like abuse and neglect, biochemical differences, personality types, and certain environments may be associated with depression.

Learn more about the most common risk factors for depression.

Adverse experiences and challenging environments

Living through highly stressful experiences, especially during childhood, may be linked to developing depression for some people.

Traumatic experiences, like physical and mental abuse or significant losses, may increase the chance someone develops a mental health condition, including depression.

Research from 2021 suggests that family mental illness and sexual abuse significantly increase the likelihood of someone developing depression, as does exposure to bullying during the early years.

Growing up with one or more close relatives with depression may also be a contributing factor, but not only because of genetics. A parent with depression, for example, may be less emotionally available or have limited emotional resources to respond to a child’s needs.

Cultural factors and environmental changes also play a role in mental health outcomes.

For example, immigrants may face additional stressors that increase the chance of depression, like acculturation pressures, language barriers, discrimination, and conflicting identities.

Biochemical changes

Serotonin, dopamine, and norepinephrine are neurotransmitters (chemical messengers in the brain) typically associated with mood regulation. Changes in the levels of these chemicals may increase the chance of depression.

For example, low serotonin levels have been proposed as a contributing factor in the development of depression, even though some research has not found a significant correlation. However, the first line of pharmaceutical treatment for depression often includes selective serotonin reuptake inhibitors (SSRIs), a class of antidepressants that boost serotonin levels in the brain.

Substance use may also alter brain chemistry and could increase the chance of depression symptoms in some people, especially those who may be predisposed to it.

Personality

Some personality traits and disorders have been associated with symptoms of depression, like:

Some research has also found that having certain personality traits may be protective against depression.

Research from 2023 found that:

  • extraversion was negatively correlated with fatigue and low motivation (higher extraversion equals lower fatigue)
  • agreeableness had a negative correlation with guilt, as well as thoughts of death and suicide (higher agreeableness equals fewer self-harm thoughts)
  • openness was negatively correlated with a sense of worthlessness (higher openness equals lower sense of worthlessness)

Other research also suggests that people with high neuroticism, obsessive-compulsive personality disorder (OCPD), dependent personality traits, and borderline personality disorder may all be more likely to have recurrent depression.

Depression may have a genetic component, but genes are not the sole cause of the condition. Experts suspect an interplay between genetics, environment, and personal experiences is at the core of someone developing depression.