Attentional bias toward threatening stimuli in major depressive disorder: A free-viewing eye-tracking study

Limited evidence exists regarding negative attentional bias toward threatening stimuli in patients with major depressive disorder (MDD). This cross-sectional study aimed to explore attentional bias toward threatening stimuli in patients with MDD.

Hamilton Depression Scale-24 items (HAMD-24) and Hamilton Anxiety Scale (HAMA) were used to assess all participants. The MDD and healthy participants freely viewed images with positive, threatening, and neutral valence for 1000 ms, during which eye movements were recorded with the Eyelink system. Eye-tracking metrics including the mean fixation duration, mean fixation counts, mean saccade counts, mean saccade velocity, mean saccade amplitude, and mean pupil diameter were compared between MDD and healthy groups. Correlations between eye-tracking variables and both HAMD-24 total scores and factor scores were analyzed.

The study included 100 MDD participants and 100 matched healthy controls. The MDD patients had longer mean fixation duration and reduced saccade counts on threatening and neutral images compared to the healthy controls. Additionally, the MDD patients showed prolonged mean fixation duration and reduced mean fixation counts and saccade counts when viewing threatening images compared to positive images. In contrast, no bias was observed in the healthy controls. Regarding mean pupil diameter, MDD participants showed greater mean pupil diameter for threatening images compared to neutral and positive images. No significant differences were observed in mean saccade velocity and saccade amplitude between the groups. There were positive correlations between mean fixation duration on threatening stimuli and retardation factor scores of HAMD-24.

Patients with MDD exhibit abnormal attentional bias toward threatening stimuli, which is associated with the severity of retardation symptoms in MDD.