Biological Reasons for Depression

Depression is complex, as Hara Estroff Marano writes in Psychology Today. Many factors contribute to its development. Yet one cannot ignore the fact that depression is, at least in part, a biological illness.

Genes

• Those with a family history of the condition are more likely to develop depression. Scientists have not yet found a single gene that "causes" depression; instead, many genes combine with environmental factors to cause the illness.

The Brain

• Depression clearly involves the brain. This is apparent because, compared to healthy individuals, those who have depression have certain brain structures that are smaller than average.

Chemical Imbalance

• Depression also arises due to chemical imbalances in the brain. The exact relationship between brain chemicals and major depression is unclear; however, it may be that chronic chemical dysregulation damages brain structures and thereby results in depression.

Serotonin Theory

• Serotonin is one important neurotransmitter that is often dysregulated in cases of depression. Medications such as selective serotonin re-uptake inhibitors (SSRIs) are effective treatments for the disorder.

Cortisol

• The stress hormone cortisol also influences the development of depression. Stressful events trigger its release; chronic exposure damages the brain and dysregulates the balance of chemicals in the brain.