The study, which appears in this week's Neuroscience, sheds new light on the phenomenon of panic disorder -- the intensely fearful "out-of-the-blue" symptoms that are often confused with a heart attack.
A tendency toward panic disorder and panic attacks is often passed down in families, and researchers have long suspected a genetic component. Recent animal studies have indicated that a genetic abnormality disrupts the balance of serotonin (a chemical messenger in the brain) and may increase risk for the disorder.
This newest study -- the first involving humans -- shows in brain scans that a type of serotonin receptor is reduced by nearly one-third in people at risk for panic disorder, reports researcher Alexander Neumeister, PhD, with the National Institutes of Health.
In his study, Neumeister used brain scans and MRI (magnetic resonance imaging) to visualize the brains of 16 people with panic disorder and 15 people with no history of panic disorder. Seven of the panic disorder patients also had co-existing major depression.
Using radioactivity to scan the brain, researchers were able to view serotonin receptors and their positions in the brain -- finding that receptors were reduced by nearly one-third in many regions of the brain, especially those regions involved in controlling anxiety.
They found specific brain areas of reduced serotonin activity only in the patients with panic disorder, including those who also had depression. The same receptors have been recently linked to major depression and suicide, writes Neumeister.
The results show that this "may be a source of vulnerability in humans," he writes. It is also more evidence that panic disorder and depression have "important genetic overlaps."