Disaggregation of between- and within-subject effects of internalizing symptoms on P300 amplitude during adolescence

Deviations in P300 activity have been implicated in depression and anxiety; however, much of this research has been conducted in adult samples and has primarily examined the association between P300 amplitude and internalizing symptoms between participants. We sought to simultaneously examine the between- and within-subject associations between depression and anxiety symptoms with P300. Self-report and neural data from a flanker task were collected at three timepoints over the course of two years in a large sample of adolescents (n = 490). Blunted P300 was robustly related to elevated between-subject depression. Conversely, elevations in within-subject anxiety were associated with larger P300. Results implicate the P300 as a reliable correlate of between-subjects level depression-related deficits in cognitive functions that is not susceptible to within-subject changes. Additionally, P300 also serves as a correlate of within-subject elevations in youth anxiety symptoms likely reflecting greater hyperarousal at the time of assessment.