Abstract
Preschool-onset major depressive disorder (PO-MDD) is an impairing pediatric mental health disorder that impacts children as young as three years old. There is limited work dedicated to uncovering neural measures of this early childhood disorder which could be leveraged to further understand both treatment responsiveness and future depression risk. Event-related potentials (ERPs) such as the P300 have been employed extensively in adult populations to examine depression-related deficits in cognitive and motivational systems. Few studies examine the prospective relationships between depression and P300, especially in young children. Moreover, limited research examines the relationship between P300 with psychotherapy treatment responsiveness in youths. The current study sought to examine the prospective relationships between pre-intervention P300 (i.e., choice-locked) elicited from the doors task in depressed preschool children (i.e., PO-MDD; ages 3-to-6) with reductions in depressive symptoms after completing an 18-week long dyadic psychotherapy intervention (n = 59). We also explored relations to risk for depression assessed at a follow-up visit during preadolescence (ages 8-to-12; n = 82). Those with PO-MDD exhibiting reduced choice (doors)-locked P300 demonstrated worse treatment response to psychotherapy and were more likely to meet criteria for depression during preadolescence. Moreover, the relationship between pre-intervention P300 and later preadolescence depression was significantly mediated by response to treatment. These findings suggest that deficits in brain systems linked to the choice-locked P300 component (i.e., cognitive and motivational) might be indicative of non-responsiveness to early dyadic psychotherapeutic intervention efforts for depression which impacts risk for recurrent patterns of depression in youths.