"Hopefully we'll be able to use that eventually to determine what kind of treatment to provide to people," lead author Jack Nitschke, of the University of Wisconsin-Madison School of Medicine and Public Health said in a statement.

The study, published in the American Journal of Psychiatry, used functional magnetic resonance imaging to examine patients with generalized anxiety disorder and found high levels of amygdala activity -- a part of the brain involved in memory of emotional reactions

This response in a "safe" lab settings was a disproportionately large response to the idea that something negative might happen, Nitschke said.

"It suggests that there are differences in anticipatory brain processing in these individuals," he said. "That's the crux of what's debilitating in people with anxiety disorders, whether it's panic disorder, obsessive compulsive disorder or post-traumatic stress disorder."

However, these patterns of brain activity may hold predictive power on how these patients will respond to treatment. After an eight-week course of treatment with a common antidepressant, clinical improvement was associated with higher levels of pre-treatment brain activity, Nitschke said.