Unipolar depression is a common comorbidity in children with ADHD with rates ranging from 12-50%. Compared to children with ADHD alone, children with comorbid ADHD and depression require more intense interventions since they experience higher levels of stress and more psychosocial and familial problems. One mechanism hypothesized to underlie the relationship between ADHD and depression is emotion dysregulation. Cross-sectional and longitudinal research has shown that emotion dysregulation mediates the relationship between ADHD and depression. However, there are a number of limitations in the extant literature regarding emotion dysregulation as a mechanism underlying the relationship between ADHD and depression. This article aims to review those limitations and propose that by examining a specific type of emotion dysregulation, poor frustration tolerance, we may gain critical insight into the mechanisms underlying ADHD and depression. We discuss the construct of frustration, its neural basis and evidence that poor frustration tolerance is a key impairment in children with ADHD. We conclude by suggesting that poor frustration tolerance may be a key mechanism underlying the relationship between ADHD and depression, and provide recommendations for how future research can utilize affective neuroscience techniques to examine the neural, behavioral and clinical correlates of frustration tolerance in children with ADHD to more comprehensively examine this relationship.
Keywords: ADHD; Commentary; Comorbid ADHD and depression; Depression; Developmental disorders.