Early childhood shyness could predict teen anxiety, according to a recent study.

Infants who frequently react to unfamiliar objects, people, and situations by becoming afraid and withdrawing are referred to as having a behaviorally inhibited temperament. As they grow up, many continue to be inhibited or reticent when they experience new things, including meeting new people.

Researchers from the University of Maryland, the National Institute of Mental Health and the University of Waterloo found that inhibited children are more likely than their peers to develop anxiety problems, especially social anxiety, as they get older. The new longitudinal study suggests that behavioral inhibition that persists across early childhood is associated with social anxiety in adolescence, but only among youth who were insecurely attached to their parents as infants.

Social anxiety disorder is one of the most common psychiatric disorders among children and adolescents, with rates of about 5.5 percent among 13- to 18-year-olds.

Our study suggests that it is the combination of both early risk factors that predicts anxiety in adolescence, particularly social anxiety," Erin Lewis-Morrarty, research associate at the University of Maryland, said in a statement. "The findings can inform the prevention and treatment of adolescent social anxiety by identifying specific factors that increase risk for this outcome among children who are persistently shy."

For the study, researchers collected and analyzed data from 165 European-American, middle- to upper-middle-class adolescents (ages 14-17 years) who were recruited as infants at 4 months.

At 14 months, infants and their parents were observed in the lab to see how the babies responded to brief separations from their parents. Infants were classified as having a secure or insecure attachment (to their parent) based on this observation. Securely attached infants initiated contact with their parents after separation and, if they had been upset, they could calm down when their parents returned. Insecurely attached infants showed one of two patterns: Either they ignored or avoided contact with their parents after being separated, or they wanted to be physically close to their parents but were angry and unable to calm down when their parents returned.

Years later (when the children were 14 to 17 years old), participants and their parents completed questionnaires about the adolescents' anxiety.

Researchers found that children who were both insecurely attached to their parents as infants and who were inhibited throughout their childhoods went on to have higher levels of anxiety as adolescents, specifically social anxiety. Teen males who were insecurely attached to their parents as infants and who were inhibited across early childhood were at the most risk for social anxiety. In addition, the association between childhood inhibition and adolescent social anxiety was strongest for children who reacted angrily and weren't able to calm down when reunited with their parents (during the lab task at 14 months), compared to children who showed other types of attachment patterns as infants.

Previous studies have examined either infant attachment or behavioral inhibition as risk factors for anxiety separately, but not both risk factors together.

The findings are detailed in the journal Child Development.