We hear a lot about anxiety and depression around the holidays – people feeling lonely and far from family or overloaded with stress. Although we may think of anxiety and depression separately, they often go hand in hand. Scientists are now working to better understand the different types of anxiety people experience, and a new study has found important markers for specific symptoms of anxiety in brain connectivity patterns. This work could help identify risk factors and treatments for anxiety in both clinical and healthy populations.
The new study uses fMRI to study individuals with varying symptoms of anxiety or depression. “In the ‘healthy’ population, there is a continuous range from people who are generally low-anxious to people who are more prone to worry and anxiety,” says Janine Bijsterbosch of the University of Oxford.
Working with Sonia Bishop, Stephen Smith and others, Bijsterbosch, wanted to look at “resting state” brain activity – when people are not actively engaged in a task in people – to identify changes in brain connectivity that underlie different cognitive and physiological anxiety. Cognitive anxiety refers to worrying and drawing negative interpretations about things that happen to you and that may happen in the future. Physiological anxiety includes symptoms of your heart racing, difficulty sleeping, or having butterflies in your stomach.
“We used task-free resting state fMRI, so our findings reflect changes in brain connectivity that are apparent in high-anxious people even when they are not doing anything in particular,” Bijsterbosch says. Previous studies have looked at changes in amygdala connectivity, as the amygdala is hyperactive in people with anxiety and is known to be involved in fear and threat detection. “In this study, we wanted to build on previous findings by extending the focus from just the amygdala to a wider set of brain regions,” she says.
The study revealed that the insula is an important region for distinguishing individuals with symptoms of anxiety versus depression. “We were somewhat surprised to find that altered amygdala connectivity did not play a larger role in differentiating profiles of anxious and depressed affect,” Bijsterbosch says. The researchers found reduced connectivity between the bilateral anterior and posterior insula for anxiety, controlling for depression. “We now hypothesize that the insula mediates connections between the amygdala and regulatory brain regions in the prefrontal cortex, and we hope to test this hypothesis in future work.”
Before looking at a subset of participants using fMRI, the researchers asked 379 participants fill out questionnaires that measured a wide range of cognitive, affective, and physiological features of anxiety and depression. The researchers then used a ‘hierarchical clustering’ approach to control for depression versus anxiety, as well as for “worry” and other sub-dimensions of anxiety. “We believe this novel method is particularly useful because it may help to map the resting-state correlates of symptomatology experienced by different individuals, cutting across traditional DSM diagnostic labels,” Bijsterbosch says.
“The results of our study highlight the insula as playing a key role in anxiety in general, and specifically in physiological anxiety,” Bijsterbosch says. “The insula may be an important node allowing crosstalk between subcortical regions such as the amygdala and other frontal regions such as the ventromedial prefrontal cortex.”
The hope, she says, is that the findings help explain why some people show more physiological or cognitive types of anxiety. “We are keen to extend this work to look in more detail at changes in connectivity linked to depression, and also to see how brain connectivity of people who have specific fears – such as phobias of spiders – differs from people who feel more generally anxious.”
-Lisa M.P. Munoz
The paper, “Resting State Correlates of Subdimensions of Anxious Affect,” Janine Bijsterbosch et al, was published in the Journal of Cognitive Neuroscience online on October 29, 2013. The work was funded by the National Institute of Mental Health, as well as the European Research Council.
Media contact: Lisa M.P. Munoz, CNS Public Information Officer, email@example.com