What are the causes of depression?

Feeling down is a normal part of life, especially after certain events like a breakup, being let go from a job or the loss of a loved one. While many people recover from these periods, others may experience persistent symptoms of what may develop into major depressive disorder. Severe depression can affect various aspects of life, making it hard to carry out responsibilities and daily tasks.

According to the National Institute of Mental Health, almost 15 million adults in the U.S. experienced at least one debilitating depressive episode in the past year. Although depression can often be distilled down to a possible imbalance of certain neurotransmitters or chemicals in the brain, the actual causes of depression can vary. Research is ongoing on the potential causes, but scientists have identified some likely risk factors, including genetic predisposition and chronic illnesses.

Biochemical Factors

Depression is a complex mental disorder with multiple factors. One of the main aspects to consider is the anatomy of the brain. Several areas in the brain may be involved in emotion regulation, and changes in these areas may contribute to depressive symptoms. Some key areas of the brain that may be involved in depression are:

• Amygdala: Deeply linked to emotions, the amygdala has increased activity during sadness or depression, which may lead to its enlargement.
• Basal Ganglia: These structures, associated with movement and emotion, have shown structural changes, like shrinkage, in those with depression.
• Hippocampus: Vital for long-term memory, the hippocampus is smaller in some people with depression, possibly due to prolonged exposure to stress hormones.

Genetics and Family History

Genetics may also play a part in the causes of depression. Researchers have found that depression tends to run in families, with studies suggesting that around 50% of the cause is genetic and the other 50% is unrelated to genes, such as psychological or physical factors. However, the overall impact of genetics on depression can vary. In some cases, the tendency to become depressed is almost entirely genetic, while in other cases, it may not be genetic at all.

There are likely multiple genes that contribute to a person’s risk of developing depression instead of a single "depression gene." These genetic factors, combined with environmental factors, may determine a person's susceptibility to depression.

Psychological Factors

One key psychological aspect that may contribute to depression is a person’s personality. Certain personality traits, such as high neuroticism, introversion and a tendency to over-criticize oneself, may increase the risk of developing depression. In addition, the way a person thinks, copes and reacts to certain stressful events may also affect the onset of this mental health condition.

Low self-esteem is another significant psychological factor in depression. When an individual has a negative self-image or feels unworthy, they may be more susceptible to feelings of sadness and hopelessness. These emotions can worsen depressive symptoms and create a vicious cycle in which low self-esteem leads to depression, further decreasing self-esteem.

Lifestyle and Physical Factors

Lifestyle factors, including overworking, poor diet, inadequate sleep and insufficient time for relaxation, may be causes of depression. In some cases, medical conditions, such as chronic illnesses or hormonal imbalances, may trigger depressive symptoms.

Environmental Factors

Environmental factors can also contribute to the development of depression. For example, a disorganized home environment or disrupted parent-child relationships, such as those caused by maternal depression, could increase the risk of depression in children.

Traumatic experiences and negative events in a person's life can also be causes of depression. People exposed to abuse, violence or loss might be more susceptible to developing the condition. In addition, living in areas with high levels of pollution, noise and limited green spaces has been linked to higher depression risk.

Sources:

• https://www.nimh.nih.gov/health/statistics/major-depression
• https://www.health.harvard.edu/mind-and-mood/what-causes-depression
• https://med.stanford.edu/depressiongenetics/mddandgenes.html
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2724169/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3518491/
• https://www.nih.gov/news-events/nih-research-matters/factors-affect-depression-risk