Developmental Depression in Adolescents: A Potential Sub-type Based on Neural Correlates and Comorbidity.

Diagnosis of depression has low reliability (kappa = 0.28) due to "covert heterogeneity," making the identification of sub-types a focus of research. Very high rates of moderate or sub-threshold depression among adolescents (35-45 % beyond the 20-25 % with MDD), prompt consideration of a potential sub-type of moderate sub-threshold depression, linked to adolescent development. Previously, developmental depression (DD) has been proposed as sub-type of moderate depression that is a normative developmental process of spiritual individuation, the integration of existential and spiritual experience. DD as a potential sub-type is supported both by clinical observation and by an emerging body of research identifying a common physiology to underlie both depression and spirituality (neurotransmitters, structural MRI and long-term clinical course), as well as research showing a surge of spirituality in adolescence (concomitant with window of risk of depression). We test for unique patterns of comorbidity and neural correlates as support for a sub-type. Based upon existing literature, we propose that DD will be (1) associated with the unique neural correlate of increased volume in the occipital region and (2) co-morbid with symptoms of affected regulation and processing. A sample of 125 adolescents (64 girls and 61 boys; ages 15-19 years) from the larger National Institute of Health Magnetic Resonance Imaging (MRI) Study of Normal Brain Development (Evans in Neuroimage 30(1):184-202, 2006) was assessed using the Cloninger Self-Transcendence Scale to examine correlates of sub-threshold mild to moderate symptoms of depression. Findings lend support to the possibility of a DD. Sub-threshold depression was associated with greater volume in the occipital region, as well as comorbidity with symptoms of affected regulation and processing (mania, ADHD, anxiety). By contrast, in adolescents with a low level of transcendence, sub-threshold depression was associated with conduct disorder and heavy substance use, both of which previous research have found to be associated with low levels of personal spirituality.