Lower recognition thresholds for sad facial expressions in subthreshold depression: a longitudinal study

Subthreshold depression (StD) is more prevalent than major depressive disorder (MDD) all over the world. Previous studies have indicated that depression is associated with impaired perception of facial expressions. However, for individuals with StD, whether perceptual sensitivity toward facial expressions could be altered and whether these alterations could stabilize over time remain largely unknown. Using the QUEST psychometric procedure, here we assessed recognition thresholds of five facial expressions (angry, fear, happy, sad and neutral) for individuals with StD and non-depressed controls. These subjects were retested after approximately 2-month time intervals. At the initial assessment, individuals with StD demonstrated lower recognition thresholds (i.e., stronger sensitivity) for only sadness compared to non-depressed controls. At the follow-up assessment, we classified the StD group as two subgroups: the non-remitted and the remitted group. For the former, lower recognition thresholds for only sadness were again found; for the latter, there was no significant difference. More importantly, individuals displaying lower recognition thresholds for sadness at the initial assessment were less likely to improve in depressive symptoms at the follow-up assessment. These results indicate that the alteration of perceptual sensitivity toward the sad expression for individuals with StD is associated with the current clinical state.