BBC Science's Tracy Logan: Anxiety disorders cause severe disabilities

The new mouse is more afraid of raised, open walkways than normal mice, but its worries can be treated with doses of Valium-type drugs. It is the first mouse to have a defined genetic mutation related to the biological mechanisms which cause anxiety disorders in humans.

About 25% of people develop an anxiety disorder at some time in their lives. These include phobias, panic attacks and post-traumatic stress disorders (PTSDs) which can have devastating effects on people's lives.

The disorders are partly determined by life experience, but genes are likely to play a role too. For example, it is more likely for identical twins (who have identical genes) both to suffer PTSD after war combat than non-identical twins.

Model mouse

The mouse was developed by a team at the Swiss Federal Institute of Technology and the University of Zurich and reported in the journal Nature Neuroscience.

Commenting on the research, Stephan Anagnostaras, a neurobiologist at the University of California, Los Angeles, said: "The mutant mice may represent a good genetic model because they are likely to overreact to many anxiety-provoking situations."

Professor Anagnostaras said there were three areas where the mice could be useful:

• Improving drug discovery.
• Predicting the mutations that may occur in people with anxiety disorders.
• Studying how genes and environment interact to give anxiety disorders.

The anxious mice were bred to have a mutation in the gene which controls the brain receptor for GABA, an important neurotransmitter.

"Hairy mouse" is used to investigate hair loss (Photo: Linda Degenstein and Chuck Wellek)

When faced with elevated walkways without a restraining wall, they spent less than half the time exploring than unmutated mice - they were frightened. However, when treated with diazepam, similar to Valium, they were just as brave as the normal mice.

In another test, the anxious mice spent about 40% less time in the more brightly-lit areas of a maze, preferring to hide in the dark. Again, treatment with diazepam removed the differences.

The fact that the diazepam has the same effect as it does in humans suggests that the underlying mechanism is similar. This mechanism is still not completely understood but the nervous mice's twitchy behaviour will certainly help to reveal it further.