Mom always said, “Choose your friends wisely.” Now a study led by a Rutgers Health professor shows she was onto something: Their traits can rub off on you – especially ones that are in their genes. The genetic makeup of adolescent peers may have long-term consequences for individual risk of drug and alcohol use disorders, depression and anxiety, the groundbreaking study has found.

“Peers’ genetic predispositions for psychiatric and substance use disorders are associated with an individual’s own risk of developing the same disorders in young adulthood,” said Jessica E. Salvatore, an associate professor of psychiatry at the Rutgers Robert Wood Johnson Medical School and lead author of the study published in the American Journal of Psychiatry. “What our data exemplifies is the long reach of social genetic effects,” Salvatore said.

Socio-genomics – the influence of one person’s genotype on the observable traits of another – is an emerging field of genomics. Research suggests that peers’ genetic makeup may influence health outcomes of their friends. To test this, Salvatore and colleagues used Swedish national data to assess peer social genetic effects for several psychiatric disorders.

With an anonymized database of more than 1.5 million individuals born in Sweden between 1980 and 1998 to Swedish-born parents, the first step was to map individuals by location and by school during their teenage years. The researchers then used medical, pharmacy and legal registries documenting substance use and mental health disorders for the same individuals in adulthood. To read the full story.