A combination of genes and neglectful parenting may make some young people more vulnerable to major depression, new research conducted in northern Russia suggests.

In a study of 176 teenage boys recruited from a juvenile detention center, researchers found a higher depression risk among those who had both a neglectful mother and a particular variant of a gene called DAT1, or the dopamine transporter gene. DAT1 helps regulate brain levels of dopamine, a chemical “messenger” that transmits nerve impulses among cells.

While the gene variant and a neglectful mother together affected depression risk, neither one alone did, the study found.

The findings, published in the journal Psychological Science, add to evidence that depression is a product of both nature and nurture.

“This study indicates that people with a particular variant of the DAT1 gene may be at heightened risk for depression when stress occurs - in this case, maternal rejection,” explained lead researcher Dr. Gerald J. Haeffel, of the University of Notre Dame in Indiana.

It’s known that stressful life events play a major role in depression, Haeffel told Reuters Health, but not everyone becomes depressed in response to such experiences. So, he said, “it is critical to determine what makes some people susceptible to depression in the face of stress, whereas others are resilient.”

Most research on the gene-environment interaction in depression has focused on genes regulating serotonin, a brain chemical involved in mood. But dopamine activity has also been linked to depression.

Dopamine plays a role in a range of vital functions, including movement, emotional responses and the capacity to feel pleasure. For their study, Haeffel and his colleagues focused on three variations in the DAT1 gene.

The researchers tested the boys, all considered to be at high risk of depression, for the three DAT1 variants; assessed them for depression; and questioned them about their mothers’ parenting.

Overall, they found, boys who carried one particular DAT1 variant, called rs40184, and who said they were rejected by their mothers were at elevated risk of depression.

If further studies confirm these findings, dopamine could become a good target for depression therapy, according to Haeffel. Treatment would not necessarily mean taking a drug, he said.

Haeffel explained that dopamine is involved in the “approach motivation system,” which regulates people’s behavior toward goals and rewards. Behavioral therapies that, for example, help people develop new goals might help alter dopamine functioning in the brain.

“Prior work has shown that psychosocial interventions can have a significant impact on brain functioning,” Haeffel noted.

Future studies on depression, he and his colleagues recommend, should look at the interaction between environment and the DAT1 gene, as well as other genes related to dopamine.

SOURCE: Psychological Science, January 2008.