Q.

Episodes of depression seem to be common over several generations in my family. Is depression genetic?

A.

There is substantial evidence that depression is a hereditary disease. A depression gene known as 5-HTTLPR has been found.

The World Health Organization reports that more than 120 million people worldwide suffer from depression. At least 10 percent of people in the U.S. will experience major depressive disorder at some point in their lives. Two times as many women as men experience major depression.

In 2011, Dr. Srijan Sen, a professor of psychiatry at University of Michigan, and his team of researchers reported that people with a short variation of the serotonin transporter gene are more likely to become depressed under stress than those with the longer variation.

Serotonin is a neurotransmitter, a chemical substance that transmits impulses across the spaces between nerve cells. Alterations in serotonin levels in the brain can influence mood.

The 5-HTTLPR gene interferes with the serotonin process in the brain. Some antidepressant medications work by affecting the action of serotonin.

The Michigan research confirmed the findings of a 2003 study in which scientists established the link between genes and environment in depression. In 2009, however, an analysis of 14 studies, found no heightened risk of depression among those with different versions of the gene.

Dr. Sen’s team wanted to settle the controversy that arose after the 2009 report. The group gathered all of the 54 studies on the subject. This included data from about 41,000 volunteers.

Based on this much broader analysis, the team concluded that 5-HTTLPR does confer a greater risk of depression when combined with stress.

One of Dr. Sen’s findings is especially interesting to me. He said that it seems that people who have 5-HTTLPR are more reactive to all events, both positive and negative.

Later in 2011, a British-led international team found a DNA region linked to depression. The researchers said they believed many genes were involved in depression.

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