Researchers from Stanford University School of Medicine can predict the degree of anxiety a young child is experiencing by measuring the size of the amygdala brain region, which is associated with emotion and decision-making. In fact, they discovered that a child experiencing greater anxiety than normal had a larger amygdala with stronger connections to other parts of the emotional brain.

"We are not at a point where we can use these findings to predict the likelihood of a child developing mood and anxiety disorders as an adult, but it is an important step in the identification of young children at risk for clinical anxiety," Vinod Menon, PhD, professor of psychiatry and behavioral sciences and senior author of the study, stated in a press release.

Anxiety and the Amygdala

Although anxiety is a common emotional reaction to stress, it can lead to disabling conditions such as phobia, post-traumatic stress disorder, and generalized anxiety disorder when sustained for too long. Neuroimaging studies conducted on adults with an anxiety disorder have demonstrated one effect of prolonged stress to be an enlarged and highly connected amygdala. Shaped like an almond (from which it gets its name), the amygdala is located in an evolutionarily primitive part of the brain deep within the temporal lobe. The amygdala is the seat of intense emotion, including aggression and fear. Other studies have revealed how the amygdalae of laboratory animals placed in an environment causing chronic stress grew additional synapses; even more, synaptic connections in the brains of these animals increased in response to persistent anxiety.

To conduct the current study which appears in Biological Psychiatry, the team of researchers enlisted 76 children between the ages of seven and nine. All the children were developing typically, and none had experienced so much anxiety in daily life to be considered clinically anxious. Additionally, none had a history of neurological or psychiatric disorders, and none were using medications. At the outset of the study, each child’s parents filled out the Childhood Behavior Checklist, a standard measure of general cognitive, social, and emotional well-being. Next, the research team used magnetic resonance imaging (MRI) to measure the size of the various subregions of the amygdala, as well as a functional MRI to measure the connectivity of those regions to other areas of the brain. Then, they compared the results of the parents' assessment to the size and connectivity data for each child's brain.

What they found among the more anxious children was an enlargement in the basolateral amygdala, a subregion involved in both the acquisition and expression of conditional fear. This subregion also helps process emotion-related sensory information and communicates it to the neocortex — an evolutionarily newer part of the brain.

"The basolateral amygdala had stronger functional connections with multiple areas of the neocortex in children with higher anxiety levels," Shaozheng Qin, PhD, a postdoctoral scholar and co-author of the study, stated in a press release. Specifically, he identified four functional neocortical systems that had been impacted: One deals with perception, another with attention and vigilance, a third with reward and motivation, and the fourth with detection of salient emotional stimuli and regulation of emotional responses.

The researchers felt surprised that alterations to the structure and connectivity of the amygdala could be so significant in some of their participants, given both their ages and the fact that their anxiety levels were too low to be considered clinical. Although prolonged stress in childhood is a risk factor for developing anxiety disorders and depression later in life, these findings do not mean that every young child with an enlarged and highly connected amygdala will go on to develop a mood disorder.

Source: Menon V, Qin S, et al. Amygdala Subregional Structure and Intrinsic Functional Connectivity Predicts Individual Differences in Anxiety During Early Childhood. Biological Psychiatry. 2013.