Participants
Demographic and clinical characteristics are summarized in Table 1. One subject with MDD had been treated with Lexapro and Ambien for 7 months, but was medication-free for approximately 14 months prior to scanning. A second subject with MDD had a brief trial with Prozac which was self-discontinued prior to participation in this study. All other subjects were psychotropic medication-naïve. Fifteen subjects with MDD had experienced only one episode of depression, with length of episode ranging from 4 to 48 months, and two patients reported having two distinct episodes. Two Shapiro–Wilk tests revealed that anhedonia and irritability were both normally distributed within the MDD group, ps = 0.81, 0.48, respectively. Depression severity (excluding the anhedonia- or irritability-related items) was significantly correlated with both severity of anhedonia (r = 0.66, p < 0.005) and irritability (r = 0.66, p < 0.005) within our MDD sample. Anhedonia and irritability were not correlated (r = 0.37, p = 0.15).
Table 1  Demographic and clinical characteristics of adolescents with major depressive disorder (MDD) and healthy controls.   a Respective percentages (may not add up to 100% due to rounding). b Children’s depression rating scale – revised. c Beck depression inventory, 2nd ed. d Beck scale for suicidal ideation. e Multidimensional anxiety scale for children. f Attention deficit hyperactivity disorder. g Generalized anxiety disorder.

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