the ups and downs, and everything in between -- shape us, stay with us and influence our emotional set point as adults, according to a new study led by Virginia Commonwealth University researchers.
The study suggests that, in addition to our genes, our life experiences are important influences on our levels of anxiety and depression.
"In this time of emphasis on genes for this and that trait, it is important to remember that our environmental experiences also make important contributions to who we are as people," said principal investigator Kenneth Kendler, M.D., director of the VCU Virginia Institute for Psychiatric and Behavioral Genetics.
"When I was growing up, in talking about the importance of a good diet, we used to say 'You are what you eat.' What this study shows is that to a substantial degree, 'you are what you have experienced.' That is, your life history stays with you in impacting on your background book, for good or for ill," he said.
Kendler, professor of psychiatry, and human and molecular genetics in the VCU School of Medicine, and an international team of researchers from VCU and other universities, analyzed nine data sets of more than 12,000 identical twins with symptoms of depression and/or anxiety through the lifespan.
By studying identical twins, researchers have a pair of individuals who are born with identical genetic compositions and a shared family environment. Their environments may begin to change as they begin to make divergent decisions as they get older that come with lifestyle, diet or friends.
Participants completed reports relating to their own symptoms of anxiety and depression in a five-to-six-year period. The participants varied in age and were from American and European population-based registries.
According to Kendler, statistical models, developed by his colleague Charles Gardner, Ph.D., a research associate in the VCU Department of Psychiatry, were used to observe how components of individual variation changed over time. The team observed that as the twins moved from childhood into late adult life, they increasingly diverged in their predicted levels of symptoms, but after that point, stopped further diverging. Further, they noted that environmental experiences contribute substantially to stable and predictable inter-individual differences in levels of anxiety and depression by mid-life in adults.
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The study first appeared online Sept. 23, and in the October issue of Psychological Science, a journal of the Association for Psychological Science.