Gene may boost effects of peer pressure

Some teens show DNA-related sensitivity to substance use levels at school

All too often, high school students have to decide whether to join in on gulping down booze with the cool kids or lighting up a cigarette with parking-lot rebels. A new study suggests that genetics plays a role in the likelihood that some teens will succumb to this kind of peer pressure.

Adolescents generally report drinking and smoking a lot in schools with high levels of such behavior, and doing so relatively infrequently in schools with low levels of substance use. These trends were stronger in teens with two copies of a short version of a gene called 5HTT than peers with two long versions, sociologist Jonathan Daw of the University of Colorado Boulder reported August 18 at the American Sociological Association’s annual meeting in Denver.

Teens who had inherited one long and one short gene reported rates of alcohol and cigarette use that fell in between those of the other two groups, regardless of how much substance use occurred at their schools, Daw and his colleagues found. The 5HTT gene helps regulate transmission of serotonin, a chemical messenger in the brain.

Daw’s team likens teens with the two short versions of the gene to social chameleons, more likely to conform to smoking and drinking styles of students around them than teens with one or no short variants.

“Our data suggest that, alongside many other influences on adolescent substance use, genetics partly underlie individuals’ susceptibility to peer smoking and drinking,” Daw says.

The findings join a growing number of studies indicating that variants of certain genes increase a person’s sensitivity to both positive and negative aspects of their surroundings (SN Online: 4/6/11), says psychologist Michael Pluess of King’s College London. But because Daw and his colleagues failed to account for family factors linked to teen substance use, such as household income and parenting quality, “adolescents with the short gene are more likely affected by the family environment they grow up in rather than social norms at school,” Pluess says.

Daw doubts that his findings primarily reflect family influences on teens’ alcohol and cigarette use. His team analyzed data from a national study launched in 1994, known as Add Health, that tracked teens into adulthood.There were 14,560 students from 80 high schools in the study who provided DNA as adults. Among the participants were more than 2,000 pairs of siblings living in the same house and, in most cases, attending the same school.

Researchers accounted for siblings’ genetic differences as well as for family characteristics shared by brothers and sisters, such as parents’ drinking levels, Daw says.

Twenty-eight percent of the teens studied carried two short versions of the 5HTT gene. Compared with attending a light-drinking school, attending a heavy-drinking school was associated with consuming an average of 8 more alcoholic beverages annually – 11 drinks per year as opposed to 3 — for students with two short genes, versus 5.7 more for students with two long versions of the gene.

Average annual numbers of cigarettes smoked rose by 89 — from 13 to 102 — for students with two short gene variants and by 77 for students with two long gene versions when they attended heavy-smoking schools, compared with light-smoking schools.

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.

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