The study is published in the August issue of the British Journal of Psychiatry.
Researchers Professor Richard Porter and PhD student Katie Douglas asked 68 people who had been diagnosed with severe depression to take part in a facial expression recognition task. They were shown a total of 96 faces displaying 5 basic emotions: angry, happy, sad, fearful and disgusted expressions. The participants were also shown faces displaying neutral expressions. Their performance was compared with a control group of 50 healthy individuals.
The researchers found that the control group were significantly better than the depression group at recognising facial expressions of disgust, indicating impairment in the ability of people with severe depression to recognise disgusted facial expressions.
Professor Porter, of the Department of Psychological Medicine, said: “The specific impairment we found in the ability of people with severe depression to recognise disgusted facial expressions has not been previously reported. However, disgust recognition has been shown to be impaired in patients with Parkinson’s disease who are not taking medication. 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 explanation is that people’s emotional processing is affected when they are 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 people who are successfully treated for severe depression become better at disgust recognition. If so, this could possibly be used as a marker of treatment outcome for people with major depression.
The study also found differences in the way the two groups interpreted neutral faces. Those people with depression were more likely to interpret neutral faces as sad, and less likely to interpret neutral faces as happy compared to the control group – findings which are consistent with previous research studies.
The study was funded by the Tertiary Education Commission’s Top Achiever Doctoral Scholarship.
For an interview contact
Professor Richard Porter
University of Otago, Christchurch,
Tel 64 3 372 0402