People with generalized anxiety disorder (GAD) have abnormalities in the way their brain unconsciously controls emotions.

A study conducted at Stanford University School of Medicine (SUSM) concluded this, which could open up new avenues for treatments and change our perception of how emotion is regulated in everyday life.

GAD in particular is marked by extreme feelings of fear and uncertainty; people with this disorder live in a state of non-stop worry and often struggle to do their daily tasks normally.

"Patients experience anxiety and worry and they respond excessively to emotionally negative stimuli, but it's never been clear really why," added Amit Etkin, assistant professor of psychiatry and behavioral sciences, who was the head of the study.

For the study, 17 people were recruited with GAD and 24 healthy participants and functional magnetic resonance imaging (fMRI) and a behavioural marker to compare what happened were used ,when the two groups performed an emotion-based task.

The task involved viewing images of happy or fearful faces, overlaid with the words "fear" or "happy," and using a button box to identify the expression of each face.

Not all the words matched up - some happy faces featured the word "fear", and vice versa - which created an emotional conflict for participants.

In the current study, Etkin and his colleagues found that both healthy participants and GAD patients were able to identify the expressions.

Healthy participants, as was expected, reacted more quickly to incongruent images when the previous image was also incongruent.

When later asked if they were aware of any pattern that might have helped or hindered their performance, the volunteers said they were not; Etkin said this demonstrated that this process was carried out unconsciously.

However, the researchers found that in the GAD patients, the reaction-time effect seen in healthy patients was absent - and in the most anxious patients, reaction time actually worsened when there were two incongruent images in a row.

"GAD patients had decreased ability to use emotional content from previous stimuli to help them with the task," said Etkin. He said the differences between the two groups were striking.

The work was published this month in the American Journal of Psychiatry, an online journal.