Brain activity reflects differences in types of anxiety
Diana Yates, Life Sciences Editor
217-333-5802; diya@uiuc.edu
May 29, 2007
CHAMPAIGN, Ill. — All anxiety is not created
equal, and a research team at the University of Illinois now has the data to
prove it. The team has found the most compelling evidence yet of differing
patterns of brain activity associated with each of two types of anxiety: anxious
apprehension (verbal rumination, worry) and anxious arousal (intense fear,
panic, or both).
Their work appears this month online in Psychophysiology.
“This study looks at two facets of anxiety that often are not
distinguished,” said U. of I. psychology
professor Gregory A. Miller, co-principal investigator on the study with
psychology professor Wendy Heller. “We had reason to think there were
different brain mechanisms, different parts of the brain active at different
times, depending on what type of anxiety one is facing.”
According to a recent national survey, anxiety disorders are the most commonly
reported psychiatric disorders in the U.S. The Diagnostic and Statistical Manual
of Mental Disorders classifies nearly a dozen different anxiety disorders, from
acute stress disorder to obsessive-compulsive disorder to panic attack and PTSD.
But those who study and treat patients with anxiety disorders do not always
differentiate the patients who worry, fret and ruminate from those who
experience the panic, rapid heartbeat or bouts of sweating that characterize
anxious arousal. These two kinds of anxiety may occur alone or in combination,
with potentially important implications for treatment.
To test whether neural activation patterns supported the hypothesis that these
two categories of anxiety are distinct, the researchers selected 42 subjects
from a pool of 1,099 undergraduate college students, using psychological tests
to categorize them as “high anxious apprehension,” “high anxious
arousal,” or neither.
Other psychological assessments standardized the pool of participants by
removing those with mood disorders or other complicating factors.
The researchers used functional Magnetic Resonance Imaging (fMRI) to map the
brain areas with heightened neural activity during a variety of psychological
probes.
As the researchers had predicted, the anxious apprehension group exhibited
enhanced left-brain activity and the anxious arousal group had heightened
activity in the right brain. The anxious apprehension group showed increased
activity in a region of the left inferior frontal lobe that is associated with
speech production. The anxious arousal group had more activity in a region of
the right-hemisphere inferior temporal lobe that is believed to be involved in
tracking and responding to information signaling danger.
Other studies using electroencephalographic (EEG) methods had found that
patients diagnosed with generalized anxiety disorder and obsessive-compulsive
disorder had heightened activity in the left brain, whereas patients with panic
disorder, panic symptoms or those subjected to high stress situations exhibited
enhanced activity in the right hemisphere.
This is the first study, however, to localize
the affected regions to identify areas within each hemisphere that seem to
matter.
Miller stressed the importance of a related finding: The researchers
distinguished the left-brain region involved in anxious apprehension from a
nearby structure that is associated with positive emotional processing.
“Left and right is not the only distinction we made,” Miller said. “We did
left/right comparisons with groups, but we also did comparisons within the left
hemisphere to show that these different areas are doing different things.”
“This is biological validation of the proposal of the psychological
differentiation of types of anxiety,” Miller said. “Whether you want to
treat anxiety psychologically or biologically – and we know that either type
of intervention affects both the psychology and the biology of the person –
these findings are a reminder that you might want to assess people carefully
before you embark on a particular type of treatment.”
This research is based on a master’s thesis submitted by graduate student Anna
S. Engels to the U. of I. The work was supported primarily by the National
Institute of Mental Health and also by the National Institute on Drug Abuse,
both at the National Institutes of Health. Support also was provided by the Beckman
Institute, the department of psychology and the Intercampus Research
Initiative on Biotechnology at the U. of I.
Miller is affiliated with the Beckman Institute; the department of psychology
and the Neuroscience Program
in the College of Liberal Arts and Sciences;
and the department of psychiatry in the College
of Medicine.
Editor’s note: To reach Gregory A. Miller, call 217-333-4507; e-mail: gamiller@uiuc.edu.
University of Illinois at Urban - Champaign: http://www.uiuc.edu/