Why do we get panic attacks?

Scientists think they may have discovered why we have panic attacks.

It's been known for over a century that breathing carbon dioxide can trigger panic attacks, and people with a condition known as panic disorder are particularly susceptible to them. Until now, no-one has been able to explain why this happens.

But scientists have discovered that the part of the brain which registers fear - the amygdala - contains a chemical sensor which can activate a fear response when acidity levels in the brain start to rise, for instance when breathing in carbon dioxide.

This may be linked to our innate fear of suffocation.

"It's interesting that evolution positioned an acid sensor right in this central circuit," said Michael Welsh, one of the authors of the study, from the University of Iowa.

"Detecting an elevated carbon dioxide is critical for survival. When you are suffocating, this circuit triggers mechanisms for escape or relief of the problem."

This discovery, published in the journal Cell, may help to explain and perhaps even correct what goes wrong in those who suffer from panic attacks, the researchers said.

In laboratory tests, mice with reduced brain acidity levels due to breathing in carbon dioxide were shown to act in a more fearful manner. When the animals were treated to prevent a fall in brain acidity, the fear response was reduced.

People prone to panic attacks and post-traumatic stress disorder may carry genetic variations which make them more susceptible to changes in brain acidity levels, the scientists said.

"It has been proposed that panic and anxiety disorders involve a suffocation alarm gone haywire," said Dr. Welsh.

"Now, this work may shed some light on this well-known phenomenon and suggests strategies for further exploration."

This article was published on Thu 26 November 2009