Perceptual Differences in Emotionally Ambiguous Neutral Faces Among Individuals Displaying Clinically Significant Insomnia Symptoms

Many psychiatric populations present deficits in the processing of neutral faces. While insomnia is associated with perceptual alterations of facially expressed fear, sadness, and happiness, the perception of neutral faces have not been explored in this population. This study compared normal sleepers and individuals experiencing insomnia symptoms in their expression intensity ratings of neutral faces. A total of 56 normal sleepers scoring <5 on the Insomnia Severity Index and 58 individuals experiencing clinically significant insomnia symptoms scoring ≥15 on the Insomnia Severity Index (19.24 ± 3.53) observed 12 neutral facial photographs from the Karolinska Directed Emotional Faces database. Participants rated the extent to which each face appeared as attractive, sad, happy, trustworthy, approachable, healthy, and sociable. The results revelated a main effect of group, F(1,117) = 4.04, p = .047, and expression, F(7, 819) = 39.08, p = .001, on intensity ratings. While no significant Group × Expression interaction was confirmed, F(7,819)=1.03, p = .41, simple effects analysis determined that those experiencing insomnia symptoms rated neutral faces as significantly more attractive (34.30 ± 14.82; t(117) = −2.73, p = .007; Cohen’s d =  0.50) and happy (34.83 ± 13.87; t(117) = −2.23, p = .028; Cohen’s d =  0.41) compared with normal sleepers (Attractive: 26.89 ± 14.76; Happy: 28.90 ± 12.48). The present outcomes tentatively suggest that individuals experiencing clinically significant insomnia symptoms differentially perceive neutral faces when compared with normal sleepers. These outcomes present potentially negative psychosocial implications for those with insomnia.