The tendency to have an enhanced response to negative facial expressions is common in people with depression. The findings of a new study show that treatment can reduce this bias.

People with depression can be highly sensitive to negative events. Past studies have found that these individuals can recollect negative words and identify sad facial expressions more accurately than those not living with depression.

These findings fall into the emotional information processing category.

A new study, appearing in Biological Psychology, has investigated whether a similar pattern occurs in a different form of information processing.

Automatic information processing refers to cognitive processes that occur with little effort or attention from the person. For example, walking or driving a car.

Researchers at the University of Jyväskylä, Finland, wanted to see whether the negative bias in emotional information processing happened automatically and whether the findings changed over time.

"It is important to study the automatic processing phase because the brain constantly encodes stimuli that are outside of the conscious attention," says doctoral student Elisa Ruohonen.

Following the methods of earlier studies, the researchers chose pictures of facial expressions as the stimuli to examine whether a relationship exists between brain responses to sad expressions and the outcome of cognitive therapy.

A long-term approach

The researchers recruited equal numbers of people with and without depression for the study. They displayed various facial expression images on a screen in front of each participant but told them to pay attention to a playing audiobook and keep their gaze firmly on the middle of the screen.

During the experiment, the team asked the participants questions about the story to ensure that they were listening to it. They also recorded their electrical brain responses throughout.

Follow-ups took place for the depression group 2 months and 39 months after the initial test. The researchers measured the brain responses each time.

At the 2 month follow-up, about half of the participants with depression had undergone a short course of cognitive behavioral therapy. The 39 month follow-up saw all of the participants receive this treatment.

This staging was another deliberate decision to determine whether a reduction in symptoms affected brain responses to facial expressions.

A final questionnaire divided participants into recovered and unrecovered groups.

"Long-term follow-up studies give important insights, since many studies on treatment effects only focus on short-term outcomes," Ruohonen explains.

Bias is not permanent

In line with other findings, the results from the initial experiment showed that people with depression had a more significant brain response to sad expressions than to neutral ones.

As Ruohonen says, "The results indicate that the depression-related bias in the processing of sad facial expressions is present already in the early and automatic phase of information processing."

However, follow-up findings showed that this negative bias is not permanent and that it can, in fact, decrease when symptoms lessen.

The brain responses at baseline did not help predict which individuals would recover with treatment. They may, however, prove applicable in identifying depression itself.

Although the study was long-term, it is still unclear if the bias that it focused on "is a cause or a symptom of depression," Ruohonen notes.

Further research with a bigger sample size and equal gender distribution may achieve stronger or different findings.

"We aim to find brain response markers that could be used to predict treatment response," Ruohonen states, adding: "It is important to take into account the heterogeneity of depression and individual factors that could affect treatment response."

"One study focus could be to investigate whether depressed participants that have stronger negative bias benefit from treatment that specifically targets this bias."

—Elisa Ruohonen