By Eszter Szekely, Ph.D.
Peer relationships are important for children’s mental health. Yet, little is known about the factors that shape them. Children tend to organize into networks, which represent how they are connected to each other along such dimensions as friendship, rejection, or supporting one another. In this study, we asked two questions. First, does a child’s position within the classroom peer network reflect the child’s earlier mental health trajectory? Second, are these network positions—that is, the way a child is connected to his peers—heritable?
Does a child’s position within the classroom peer network reflect the child’s earlier mental health trajectory?
We worked with colleagues in the Generation R Study Group based in Rotterdam, the Netherlands. They followed the social-emotional development of 1,288 Dutch children from age 18 months to 8 years. A great strength of this study was the availability of DNA in all children, which helped us determine the degree of genetic influence on children’s peer network positions. We used a recently developed method to estimate the combined effect of more than half a million common genetic variants on children’s peer network positions. This measure of genetic influence can best be thought of as an estimate of heritability that utilizes DNA alone in samples of unrelated individuals rather than relying on twins and families to infer genetic relatedness.
Parents provided detailed reports on their children’s emotional and behavioral problems at three time points: 18 months, 3 years, and 5 years of age. These reports were used to chart the early developmental course of children’s mental health during the preschool period. When participants were 6 to 7 years old, their entire classroom peer networks were mapped. We were interested to know what positions children occupied within their peer networks along the dimensions of friendship, peer rejection, and social support and whether these positions were associated with earlier mental health.
Are network positions—that is, the way a child is connected to his peers—heritable?
There were two key findings. First, children with an early history of being chronically aggressive, impulsive, or inattentive were later actively rejected by their peers and had few mutual friendships. In contrast, children who had a previous history of being persistently sad, moody, or overly anxious were later not actively rejected by their peers but had less dense social support networks than children who were not persistently sad, moody, or overly anxious. This suggests that the exact type of emotional or behavioral problems a child has early in life might partly determine the specific difficulties this child will later experience in peer relationships.
Children with early history of aggressiveness, impulsivity or inattentiveness were later actively rejected by peers
Interestingly, there was one network characteristic that emerged as being significantly heritable regardless of network function (defined by friendship, rejection or social support). This property is referred to as “closeness centrality” and reflects how close a child is to every other member in the network. Higher values mean fewer “steps” from network members; therefore, the child can reach (and potentially utilize) social resources more quickly. Conversely, lower scores indicate being further away from network members thus resources would need to “flow through” many other peers to reach the child.
The heritability of closeness centrality was not accounted for by mental health trajectories, which suggests that other traits may influence mental health. Mental health trajectories and closeness centrality may have largely non-overlapping genetic components that could be tested by examining the genetic overlap between them in future studies with a larger sample size. The information from this study supports findings from previous studies; therefore, we propose an intervention that may help children with peer relationship problems. The friendship networks of a classroom could be rewired with the help of a peer leader who is highly central within the classroom network. This approach may promote social inclusion, increased peer relationships, and the number of reciprocated friendships.
These findings are novel in many ways. Firstly, they suggest long-term links between a child’s early emotional and behavioral problems and later position within peer networks. Second, they show that a key property of a child’s position in a network—closeness centrality—is partly heritable. This “social” property thus might be a useful target for future genomic studies. The long-term hope is that understanding peer networks could help us intervene at the classroom level to promote childhood mental health.
The study by Szekely et al. appears in the Journal of Child Psychology and Psychiatry in June 2016 http://onlinelibrary.wiley.com/doi/10.1111/jcpp.12493/abstract.
About the Author
Eszter Szekely, Ph.D.
Dr. Eszter Szekely is a postdoctoral research fellow in Dr. Philip Shaw’s Section on Neurobehavioral Clinical Research within the Social and Behavioral Research Branch of the National Human Genome Research Institute. She completed degrees in clinical child and adolescent psychology, cognitive neuroscience, and epidemiology and received her Ph.D. in psychiatric epidemiology from the Erasmus University Medical Center in Rotterdam, the Netherlands. In her current research, Dr. Szekely combines genomic, neurobiological, and social-behavioral information to better understand common childhood mental health problems.
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