Depressed less likely to recognise disgust - study

New research on New Zealanders shows psychiatric patients with severe depression find it harder to interpret facial expressions than healthy people - particularly expressions of disgust.

The study, to be published in the August issue of the British Journal of Psychiatry, was carried out by Otago University researchers Katie Douglas and Professor Richard Porter.

They showed a total of 96 images of faces to 68 people at Christchurch's Hillmorton Hospital who had been diagnosed with severe depression, and asked them to distinguish five basic emotions: angry, happy, sad, fearful and disgusted expressions.

The depression patients were also shown faces displaying neutral expressions, and their performance was compared with a control group of 50 healthy individuals from Christchurch.

The researchers found that the healthy people were significantly better than those suffering depression at recognising facial expressions of disgust.

"The specific impairment we found in the ability of people with severe depression to recognise disgusted facial expressions has not been previously reported," said Prof Porter.

"Disgust recognition" had been shown to be impaired in patients with Parkinson's disease who were not taking medication, he said. "We know that people with Parkinson's disease don't have enough of a brain chemical called dopamine. It's possible that the ability to recognise disgust is associated with dopamine dysfunction in people with severe depression as well."

Another potential explanation was that people's emotional processing was affected when they were severely depressed.

"Admission to a psychiatric hospital is stressful, and patients are removed from their usual social environment and placed in close proximity with other distressed individuals."

The researchers have called for further research into whether the trait could possibly be used as a marker of treatment outcome for people with major depression -- with their ability for recognition improving as the depression abated.

The study also found people with depression were more likely than the healthy subjects to interpret neutral faces as sad, and less likely to interpret neutral faces as happy.