Specific white matter connectivity reduced in anxiety patients

By Mark Cowen, Senior medwireNews Reporter

Patients with generalized anxiety disorder (GAD) have reduced functional connectivity between areas of the brain associated with fight-or-flight response and emotion regulation, researchers report.

The team found that GAD patients had significantly weaker white matter connections between the amygdala and the prefrontal and anterior cingulate cortex (ACC) than individuals without the disorder.

The findings "indicate that the altered structure of a neural pathway involved in both normative emotion regulation and fear extinction processes may contribute to atypical emotional processing in GAD," say Jack Nitschke (University of Wisconsin-Madison, USA) and team.

The results come from a study of 49 patients (30 women) with GAD and 39 controls without a history of psychopathologic conditions. Of the patients with GAD, 21 had a comorbid Axis I disorder.

All of the participants underwent diffusion-tensor and functional magnetic resonance imaging of the brain.

Overall, patients with GAD had significantly lower fractional anisotropy (FA) values than controls in the bilateral uncinate fasciculus - a white matter tract that connects the amygdala and ACC.

There were no significant between-group FA differences in other white matter tracts.

Further analysis showed that GAD patients without comorbid Axis I disorders had significantly lower FA values in the uncinate fasciculus than controls, whereas the difference between GAD patients with comorbid Axis I disorders and controls was not significant.

Consistent with this finding, analysis of a subgroup of 21 GAD patients without a comorbid Axis I disorder and 21 age-, gender-, and education-matched controls revealed no significant difference in uncinate fasciculus FA values between the groups.

Nitschke et al conclude in the Archives of General Psychiatry: "We identified evidence of reduced integrity of the uncinate fasciculus, a crucial white matter pathway linking ventral regions of the prefrontal cortex and ACC to limbic regions, in patients with GAD."

They add: "Decreased structural integrity of the uncinate fasciculus in patients with GAD may have detrimental functional consequences for emotion regulation, contributing to heightened anxiety."

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