A study published in Brain and Behavior teased apart the unique effects of loneliness and depression on the processing of emotional facial expressions. In a facial emotion processing task, loneliness was tied to increased accuracy in identifying sad faces, while depression was tied to decreased accuracy in identifying happy faces. Additionally, being either lonely, depressed, or both lonely and depressed was associated with mislabeling neutral faces as sad.
Previous studies have revealed that loneliness and depression are both associated with deficits in social information processing. But because the two conditions often co-occur, it is tricky to discern which deficits result from the combination of loneliness and depression, and which result from either loneliness or depression on its own. By recruiting a very specific sample of participants, study authors Survjit Cheeta and her team were able to tease apart these unique effects.
The researchers recruited four groups of participants. Using a screening questionnaire, they identified 21 participants with high loneliness and high depression scores, 11 participants with high loneliness and low depression scores, and 10 participants with low loneliness and high depression scores. A final group of 35 participants had low scores in both loneliness and depression (control group).
All subjects then performed a facial emotion processing task where they were shown a total of 144 faces on a computer screen that were expressing different emotions at different intensities. Participants were then asked to select the emotion being portrayed in the face from a list of six options — happy, sad, anger, fear, disgust, or surprise.
The researchers found that loneliness on its own was associated with greater accuracy in identifying sad faces, which is consistent with previous findings showing that lonely people are especially sensitive to certain emotional cues. However, loneliness on its own was also tied to a reduced accuracy in identifying fearful faces, which is inconsistent with this viewpoint.
Loneliness was additionally associated with a lower likelihood of labeling neutral faces as happy, which is in line with previous studies showing a negative processing bias among lonely people. Depression on its own was tied to reduced accuracy in identifying happy faces, suggesting a negative bias among depressed people which limits their accuracy in recognizing happy faces.
The study additionally uncovered a new finding — comorbid loneliness and depression was associated with misidentifying neutral faces as sad. Interestingly, both loneliness on its own and depression on its own were also associated with misidentifying neutral faces as sad. The authors say that, overall, these findings point to the importance of treating both loneliness and depression when addressing emotion processing deficits.
Cheeta and her team note that their study design required them to recruit participants who were only lonely and not depressed, as well as participants who were only depressed but not lonely. The challenges of recruiting these specific groups of individuals led to varying sample sizes in the four groups, which may have affected their findings.
The study, “Seeing sadness: Comorbid effects of loneliness and depression on emotional face processing”, was authored by Survjit Cheeta, Joseph Beevers, Sophie Chambers, Andre Szameitat, and Chris Chandler.