Anxiety disorders observed in preschoolers — including social phobia, separation anxiety and generalized anxiety disorder — can lead to physiological changes in brain development, a new study from the Yale Child Study Center shows.

The researchers imaged the brains of children with and without preschool anxiety disorders. They found that in those who had an anxiety disorder, the prefrontal cortex and the amygdala, two regions whose “cross-talk” is important in modulating anxiety, effectively talked less to each other in a phenomenon known as weaker functional connectivity. They also found that different anxiety disorders led to different connectivity patterns.

In other words, not only are anxiety disorders strongly based in biology, but they also result in physically different brains.

“Now that [we] know what a mechanistic brain characteristic of anxiety looks like in preschoolers, we have a much more reliable and quantitative [understanding of anxiety rather] than a broad diagnosis,” said Kevin Pelphrey, senior author and the co-director of the center for translational developmental neuroscience.

Helen Egger, senior author and professor of psychiatry and behavioral sciences at Duke University Medical Center, said she believes that preschool anxiety disorders are too often misperceived as transient, insignificant childhood problems. This study, she said, disproves that notion and shows that preschool anxiety disorders can leave “enduring differences in brain function.”

Preschoolers between the ages of two and five were tested using the Preschool Age Psychiatric Assessment, developed by Egger. The assessment comprises interviews with children’s parents about their children’s behavior and feelings. When those children reached the ages of five to nine, the researchers then administered fMRI scans to observe any changes in the brain.

The changes varied depending on the type of anxiety disorder, giving biological credence to Egger’s hypothesis that the different anxiety disorders are fundamentally distinct.

“It’s very interesting,” said Gabriela Rosenblau, a postdoctoral associate at the Child Study Center, noting that these anxiety disorders are typically differentiated by associated symptoms and behaviors. These findings, though, show that the disorders are also differentiated by biology, and there may be potential neural markers to distinguish them.

Whether these physical brain changes can be fixed is not known yet. Neuroscientists are still grappling with the magnitude of neuroplasticity, or to what extent grown brains can change. But Pelphrey believes there is a good chance.

“Five years ago, you would have had scientists saying, ‘[Changing brain connectivity is] not possible in adults … You’re not going to change their underlying brain biology,’” Pelphrey said. “But I think neuroscientists are more and more surprised as to just how plastic the brain is all the way through adulthood.”

According to Michael Crowley, co-director of the Center for Translational Developmental Neuroscience, the study was the first to administer fMRIs to children at such an early age. He said he thinks that looking at the biological underpinnings of anxiety can help us refine treatments and understand how to make them more “potent.”

Egger added that early treatment will be key in reducing suffering caused by preschool anxiety disorders. She also noted that treatment has to be disorder-specific — not all anxiety disorders can be clumped together.

The researchers said their next step is to test the effectiveness of various interventions by administering fMRIs to participants and observing changes in brain connectivity.

Approximately 5 to 6 percent of preschoolers suffer from an anxiety disorder. Anxiety disorders are caused by the “interplay” of genetics, biology and environmental factors.