People with generalized anxiety disorder, or GAD, have abnormalities in the way their brain unconsciously controls emotions, revealed by researchers.
The new study from Stanford University School of Medicine is published online in this month’s American Journal of Psychiatry.
According to the National Institute of Mental Health, 18 percent of Americans have an anxiety disorder. GAD in particular is marked by extreme feelings of fear and uncertainty; people with the disorder live in a state of non-stop worry and often struggle getting through their daily lives.
“Patients experience anxiety and worry and respond excessively to emotionally negative stimuli, but it’s never been clear really why,” said Amit Etkin, MD, PhD, acting assistant professor of psychiatry and behavioral sciences and first author of the study.
Etkin said clinical data have suggested that adult GAD patients initially register negative stimuli in a largely normal way, but have deficits in how they then control negative emotions.
For the study, Etkin recruited 17 people with GAD and 24 healthy participants and used functional magnetic resonance imaging and a behavioral marker to compare what happened when the two groups performed an emotion-based task. The task involved viewing images of happy or fearful faces, overlaid with the words “fear” or “happy,” and using a button box to identify the expression of each face. Not all the words matched up – some happy faces featured the word “fear,” and vice versa – which created an emotional conflict for participants.
In the current study, Etkin and his colleagues found that both healthy participants and GAD patients were able to identify the expressions. Healthy participants, as was expected, reacted more quickly to incongruent images when the previous image was also incongruent. When later asked if they were aware of any pattern that might have helped or hindered their performance, the volunteers said they were not; Etkin said this demonstrated that this process was carried out unconsciously.
However, the researchers found that in the GAD patients, the reaction-time effect seen in healthy patients was absent – and in the most anxious patients, reaction time actually worsened when there were two incongruent images in a row. “GAD patients had decreased ability to use emotional content from previous stimuli to help them with the task,” said Etkin.
During this study, the brains of healthy participants reacted as expected. But for patients with GAD, the pregenual anterior cingulate failed to light up and to inhibit the amygdala, showing something went awry with this circuit. This has never been shown before, Etkin noted.
Understanding that the prefrontal cortex is an important site of abnormality could potentially lead to advances in more accurate diagnosis and effective treatment. By targeting this region more directly, clinicians might be able to improve regulation function in GAD patients. Etkin also suspects that a faulty pregenual cingulate-amygdala circuit during unconscious emotion regulation is involved in other psychiatric disorders, such as post-traumatic stress disorder, so the work could lead to a better understanding of those conditions.
Source: Stanford University Medical Center, USA