Early family experience can reverse the effect of a genetic variant linked to depression, UCLA researchers report in the current issue of the journal Biological Psychiatry.
Among children from supportive, nurturing families, those with the short form of the serotonin transporter gene (known as 5-HTTLPR) had a significantly reduced risk for depression, found the UCLA team, under the direction of Shelley E. Taylor, UCLA distinguished professor of psychology and an expert in the field of stress and health. The research team also found that among children from emotionally cold, unsupportive homes marked by conflict and anger, those with the short form of the 5-HTTLPR gene were at greater risk for depression, as some previous research has also shown.
The 118 young adult men and women who participated in the study completed assessments of depression, early family environment and current stress. They were asked, for example, how often they had been loved and cared for, shown physical affection or insulted and sworn at by their families. Saliva samples were used to determine if the participants' standing on the 5-HTTLPR had two short alleles (s/s), a short and a long allele (s/l) or two long alleles (l/l) for the serotonin transporter gene. (An allele is any of several forms of a gene.)
The research showed that a person's likelihood of developing symptoms of depression was not predicted by the particular combination of alleles alone; rather, it was the combination of the person's environment and genetic variant s/s that determined whether the person experienced symptoms of depression, said Taylor, principal investigator on the study.
Among the study's implications is that the short form of the 5-HTTLPR is "highly responsive to environmental influence" and, rather than predicting risk for depression, its effects vary substantially, depending on how supportive the external environment is, Taylor said.