Anxiety: A Very Short Introduction - Daniel Freeman, Jason Freeman 2012

Biological perspectives on GAD
Generalized anxiety disorder

What do we know about what’s happening in the brain when we worry? Neurological research on worry is in its early days, but some insights have already emerged.

In one study, scientists asked people with GAD and non-anxious individuals to spend time thinking about a variety of faces and sentences, some of which had no emotional resonance while others were designed to induce worry. During the task, the participants’ brain activity was recorded in a functional magnetic resonance imaging (fMRI) scanner.

For both the anxious and non-anxious groups, the same areas of the brain were activated when they worried. These areas were the medial prefrontal cortex, which plays an important role in our thoughts about our self, and the anterior cingulate region, which — among other tasks — is involved in problem-solving and the processing of emotions. But there was a difference between the two groups. In the individuals with GAD, the ’worrying’ areas of the brain remained active even when they were told to stop thinking about a sentence or face and instead relax. We know that people with GAD find it extremely difficult to stop worrying; this experiment provides neurological confirmation.

When it comes to genetic influences, the evidence suggests that these are less significant for GAD than for many other anxiety disorders. The disorder seems to run in families, at least to a degree, but this seems to be overwhelmingly the result of environmental factors. No genetic influence at all was found in two twin studies, while three others estimated heritability at around 20%. Moreover, the genetic vulnerability for GAD is very close indeed to that for depression, leading some researchers to suggest that ’from a genetic perspective, MD [major depression] and GAD seemed to be the same disorder’.