July 23, 2009

Genes, Environment Shape Teen Behavior

New findings show that adolescent alcohol use and behavior problems are influenced by the interaction of genetic and environmental factors.
"In the past, research on genetic and environmental influences on behavior was often conducted in isolation," Danielle Dick, assistant professor of psychiatry, psychology, and human and molecular genetics at Virginia Commonwealth University was quoted as saying. "Some scientists were interested in genetic effects, others in environmental effects. We now know that both genetic and environmental influences are important for most behavioral outcomes and our challenge is to understand how they interact."

"This paper adds to . . . research showing that child and adolescent behavioral problems emerge from an interplay of inherited vulnerabilities and life experiences," Lisa Legrand, research psychologist at the University of Minnesota is quoted as saying. "While inherited factors may place an individual at increased risk, psychosocial or environmental exposures may either aggravate or protect against this risk. Moreover, certain environments may actually modify gene expression such that the influence of genes varies by circumstances."

"Much of the research on environmental influences on alcohol use and behavior problems focuses on the impact of parents and peers," added Dick. "While these are clearly critical environmental influences, we have found that . . . neighborhood influences also have big impacts on adolescent behavioral outcomes, and these environmental effects have not received as much attention historically."
Researchers used data from FinnTwin12, a population-based study that has followed more than 5,000 twins born between 1983 and 1987 taken from Finland's Population Registry Center. Drawing from previous findings that community-level factors such as urban/rural residency, migration rates, and prevalence of young adults can moderate the importance of genetic effects on alcohol use among 16- to 18-year olds, this study looked at their influence on behavior problems at age 12 and alcohol use at 14 years of age.

Certain environments appeared to encourage gene expression while others constrained it, observed Legrand. "The environments that produced higher heritability estimates for female behavioral problems were urban, had a relatively mobile population, and were marked by a higher percentage of older adolescents," she said. "Conversely in rural, stable, and low-adolescent settings, preadolescent behavior problems appeared to be more influenced by the rearing environment."

It could be that girls are more susceptible than boys to certain environmental influences, Legrand added. "For example, rural females may remain closer to their parents and under the influence of their monitoring and control for a longer time than rural males," she said. "This is an intriguing area for future research."

"There is now converging evidence across a number of different studies that behavioral problems in kids are associated with both concurrent and future alcohol problems," said Dick. "There is evidence accumulating from genetic studies that behavior problems may be one of the first signs of an individual at increased susceptibility for developing alcohol problems."

Taken together, she cautioned, a key message from this kind of research is that genes are not destiny. "We're not all equally predisposed to develop alcohol or behavior problems," she said, "and the environment can be a key factor in whether or not an individual ever develops problems."

SOURCE:  Alcoholism: Clinical & Experimental Research (ACER), October, 2009