Author: Gowda Shilpa
Date: November 2007
Results published in PLoS One suggest that inhalation of carbon dioxide can trigger symptoms in healthy individuals that resemble those of panic attacks in anxiety-prone individuals. These results imply that neuronal misfiring leads to the body's oversensitive reaction to changes in carbon dioxide levels. This, in turn, causes the body to believe that it is suffocating and leads to symptoms that resemble panic attacks. One implication of the findings is the possibility of inducing anxiety in the laboratory for the purpose of testing of anti-anxiety drugs.
Researchers from the Department of Psychiatry and Neuropsychology at the University of Maastricht in the Netherlands used 64 volunteers for the study, including 33 males and 21 females. The individuals were between the ages of 18 and 65 and in good general health, as defined by a lack of pulmonary or cardiovascular disease, cerebral aneurysm (weakness in the wall of a cerebral artery or vein), pregnancy, epilepsy, excessive smoking habits (such as the consumption of greater than 15 cigarettes in a day), and usage of adrenergic receptor blockers (which affects the nervous system) or psychotropic (mood-altering) medication. They were also excluded from the study if they had a family history of affective or anxiety disorders within a first-degree relative, if they reported common specific fears, or if there was any suspicion of a history of panic attacks.
The experiments were conducted as a double-blind study (both experimenter and subjects were blinded to the goal of the study) and took place within one week on four separate days. Subjects were asked to exhale to the maximum, to position an inhalation mask on their faces, and inhale their full capacity as quickly as possible. Then, they were supposed to exhale again, emptying their lungs, and refill them immediately with gas, holding their breath for five seconds before exhaling. They inhaled four different concentrations of carbon dioxide in compressed air over the course of the experiment: 0, 9, 17.5, and 35 percent.
Using the Panic Symptom List and electronic visual analogue scale, which use criteria established by the American Psychiatric Association, to measure anxiety levels, the researchers found that panic symptoms increased when increasing concentrations of carbon dioxide were administered. Moreover, the panic symptoms were more acute for younger participants of the study, between the ages of 18 and 31 years, compared to older participants, between the ages of 38 and 62 years.
The researchers believe these otherwise healthy subjects experienced panic from carbon dioxide because the buildup of carbon dioxide led their bodies to feel that they were suffocating. If indeed the perception of suffocation is responsible for panic effects, then this would bring important insight into the problem of anxiety disorders, which could then be understood as a maladaptive side-effect of evolutionary evolved biological alarms. Along these lines, Eric Griez, lead author of the paper with these findings, says, "Panic seems to be a very special kind of anxiety which can truly be called a suffocation alarm...Panic, which is the most dramatic form of acute anxiety, is the cry for life." Perhaps one possible cause of anxiety disorders could be hypersensitive responses to changes in carbon dioxide buildup in the blood. It is hoped that these findings will lead to new insight into and possible treatments for panic and anxiety disorders in the future.
Written by Shilpa Gowda
Reviewed by Jeffrey Kost, HoiSee Tsao
Published by Pooja Ghatalia.