Anhedonia, but not irritability, is associated with illness severity outcomes in adolescent major depression

Unlike adult major depressive disorder (MDD) which requires anhedonia or depressed mood for diagnosis, adolescent MDD can be sufficiently diagnosed with irritability in the absence of the former symptoms. In addition, the current Diagnostic and Statistical Manual of Mental Disorders (DSM) schema does not account for the interindividual variability of symptom severity among depressed adolescents. This practice has contributed to the high heterogeneity and diagnostic complexity of adolescent MDD. Here, we sought to examine relationships between two core symptoms of adolescent MDD - irritability and anhedonia, assessed both quantitatively and categorically - and other clinical correlates among depressed adolescents.

Ninety adolescents with MDD (51 females), ages 12-20, were enrolled. Anhedonia and irritability scores were quantified by summing related items on the Children's Depression Rating Scale-Revised and the Beck Depression Inventory. Extremes of score distribution were defined as high or low irritability/anhedonia subgroups. A significance level of p=0.01 was set to adjust for the five comparisons.

Despite all subjects exhibiting moderate to severe MDD, both irritability and anhedonia scores manifested a full and normally distributed severity range including the lowest values possible. However, only anhedonia severity was associated with more severe clinical outcomes, including greater overall illness severity (p<0.001), suicidality scores (p<0.001), episode duration (p=0.006), and number of MDD episodes (p=0.01). Similarly, only the high-anhedonia subgroup manifested more severe outcomes; specifically, greater illness severity (p<0.0001), number of MDD episodes (p=0.01), episode duration (p=0.01), and suicidality scores (p=0.0001).

Our findings suggest the significance of anhedonia as a hallmark of adolescent MDD and the need to incorporate dimensional analyses. These data are preliminary, and future prospective studies are needed to better characterize the syndrome of adolescent MDD.