The study included 76 children aged 7 to 9, which is when anxiety-related traits and symptoms can first be reliably detected, according to the Stanford University School of Medicine researchers.
The parents provided information about their youngsters' anxiety levels, and the children also underwent MRI scans of their brain structure and function.
The investigators focused on an area of the brain called the amygdala, which is a person's "fear center," and found that kids with high anxiety levels had a larger amygdala compared to children with low anxiety levels. This part of the brain, the researchers noted, had more connections to other brain regions involved in attention, emotion perception and regulation.
The researchers also developed a way to predict children's anxiety levels based on brain scan measurements of amygdala size and its level of connection to other brain areas, according to the study in the June issue of the journal Biological Psychiatry.
"It is a bit surprising that alterations to the structure and connectivity of the amygdala were so significant in children with higher levels of anxiety, given both the young age of the children and the fact that their anxiety levels were too low to be observed clinically," first author Dr. Shaozheng Qin said in a journal news release.
The study is an important advance in identifying young children at risk for anxiety disorders and improves understanding of how anxiety develops in people, according to Qin.
While the study found an association between reported levels of anxiety and the structure and connectivity of the amygdala in kids, it did not prove a cause-and-effect relationship.
The American Academy of Child & Adolescent Psychiatry has more about children and anxiety.