Oct. 11, 2006 -- The power of love from a nurturing family may trump genetic risk for depression, new research shows.
A person's childhood experiences may interact with their genes to affect their depression risk, according to the study in Biological Psychiatry's October edition.
The notion that nature (genetics) and nurture (experiences) affect health isn't new. But the UCLA study shows how complicated the nature-nurture relationship may be.
"Genes are not destiny," says researcher and UCLA psychology professor Shelley E. Taylor, PhD, in a university news release.
Some genes, she says, including the gene she and her colleagues studied, "are clearly highly responsive" to environmental influences.
"That means, among other conclusions, that there is an important role that parents and even friends can play in providing protection against the risk of depression that stress can confer," Taylor says.
Taylor's team studied 118 young men and women who were students or employees at UCLA.
Participants were 18-29 years old (average age: about 20). None had a history of serious mental or physical problems, and none was in therapy or taking medications.
Participants completed surveys to gauge their depression symptoms, self-esteem, anxiety, personality, and social support.
They also rated how loved and cared for they felt as children and whether their childhood had included experiencing or witnessing verbal or physical abuse, parental shouting or quarreling, and living with a substance abuser.
None of the participants reported childhood physical or sexual abuse.
Those reporting conflict in their childhood homes noted "fairly mild" chronic adversity, the researchers note.
The researchers also screened participants' genes, focusing on the 5-HTTLPR gene.
That gene helps transport a brain chemical called serotonin. Low serotonin levels may lead to .
The 5-HTTLPR gene comes in "long" and "short" forms. Previous studies have suggested the that gene's short form may carry greater depression risk, Taylor's team notes.
But the connection may not be that simple, according to this study.
On one hand, participants with two copies of the gene's short form were more likely to have depression symptoms if they had had negative childhood experiences.
But those with two copies of the gene's short form were actually less likely to have depression symptoms if they had had positive childhood experiences.
Having one or more copies of the gene's long form didn't produce the same patterns.
Nature & Nurture
The results suggest 5-HTTLPR gene's short form "is not a risk factor for depression so much as it reflects a sensitivity to environmental influence," the researchers write.
They explain that "in benign environments, that sensitivity assumes a protective form and in harsh environments, it confers risk for depression."
That is, the gene's short form doesn't necessarily raise or lower depression risk. Childhood experiences may make the difference, with positive, loving childhoods showing the best results.
"It indicates just how important a loving and caring family may be," says researcher Baldwin Way, PhD, in a UCLA news release.
The findings were only true for depression, not for anxiety.
And researchers caution that while the surveys checked for depression symptoms, they didn't formally diagnose depression.
Larger studies are needed to tease out ethnic genetic differences, the researchers note.