Identifying an oculomotor phenotype for adolescent depression with an interleaved pro- and anti-saccade task

Numerous studies have shown that adults with depression have distinct oculomotor alterations during saccade tasks, but whether similar alterations occur in adolescents is largely unknown. The purpose of this study was to test if eye-tracking during a structured saccade task could distinguish a group of adolescents with depression from healthy controls. We hypothesized that, due to overlapping circuitry between depression pathology and the oculomotor system, adolescents with depression would show alterations in fixation, saccade, and pupil behaviour. 51 adolescents with depression and 66 age-matched healthy controls completed the Interleaved Pro- and Anti-Saccade Task (IPAST) and several self-reported questionnaires for psychiatric symptoms. Oculomotor outcomes included fixation acquisition, fixation breaks, correct rate, saccadic reaction time, rate of correct express-latency pro-saccades, rate of express- and regular-latency anti-saccade errors, baseline pupil size, as well as pupil constriction and dilation sizes following task instruction. In comparison to healthy controls, adolescents with depression displayed impairments acquiring fixation (p<.001), made more fixation breaks in pro- (p=.023) and anti-saccade trials (p=.005), more anti-saccade errors (p=.013), more express-latency saccades overall (ps=.016), had a smaller pupil constriction in pro-saccade trials (p=.047) and had a smaller pupil dilation in pro- (p=.011) and anti-saccade trials (p=.041). No differences were found for saccadic reaction time, rate of correct pro-saccades, rate of regular-latency anti-saccade errors, pupil constriction size during anti-saccade trials, or baseline pupil size. Patients had psychiatric comorbidities and were using psychotropic medication. While this reflected clinical reality, these factors may have influenced oculomotor behaviour. Adolescents with depression had altered fixation, saccade, and pupil behaviour during IPAST. Given that many cases of adolescent depression remain undetected, accessible and objective screening approaches are highly needed. This oculomotor phenotype may be used in the development of such a screening tool to detect those at risk.