The Go/No-Go P3 and Depressive Symptoms in Adolescents: Trial-Level Change and Mean Amplitude Relate Differently to Anhedonic Versus Negative Mood Symptoms.

Prior studies have found an association between reduced P3 brain responses-a neural marker of task engagement-and increased depressive symptoms during adolescence. However, it is unclear whether P3 correlates with depression globally, or with certain facets. Existing depression studies have also typically quantified P3 as a cross-trial average, neglecting possible trial-by-trial effects. Among 72 adolescents (44% female), the current study evaluated relations of distinct depression symptom facets-anhedonia and negative mood-with P3s from a three-stimulus go/no-go task, quantified both in average- and trial-level terms. Although no relationship was evident between overall depressive symptoms and average P3 amplitudes, opposing relations were found for each symptom facet with P3 to frequent and infrequent 'go' stimuli: higher anhedonia predicted smaller P3, whereas increased negative mood predicted larger P3. Single-trial, multilevel modeling analyses clarified these effects by showing reduced P3 across stimuli types at task outset, along with greater trial-to-trial attenuation of P3 to infrequent-go stimuli, for adolescents experiencing greater anhedonia. Conversely, increased negative mood was distinctly related to larger P3 at task onset but was unrelated to amplitude change across trials. Results demonstrate differential relations for anhedonic and negative mood symptoms with P3-indicative of task disengagement versus heightened vigilance, respectively-that may be obscured in analyses focusing on overall depressive symptoms. The divergent associations for anhedonia and negative mood with P3 underscore the need to consider these distinct symptom facets in research aimed at clarifying the nature of neural-circuitry dysfunction in depression.