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Obsessive-compulsive disorder (OCD) is an impairing psychiatric condition, which often onsets in childhood. Growing research highlights dopaminergic alterations in adult OCD, yet pediatric studies are limited by methodological constraints. This is the first study to utilize neuromelanin-sensitive MRI as a proxy for dopaminergic function among children with OCD. N = 135 youth (6-14-year-olds) completed high-resolution neuromelanin-sensitive MRI across two sites; n = 64 had an OCD diagnosis. N = 47 children with OCD completed a second scan after cognitive-behavioral therapy. Voxel-wise analyses identified that neuromelanin-MRI signal was higher among children with OCD compared to those without (483 voxels, permutation-corrected p = 0.018). Effects were significant within both the substania nigra pars compacta (p = 0.004, Cohen's d = 0.51) and ventral tegmental area (p = 0.006, d = 0.50). Follow-up analyses indicated that more severe lifetime symptoms (t = -2.72, p = 0.009) and longer illness duration (t = -2.22, p = 0.03) related to lower neuromelanin-MRI signal. Despite significant symptom reduction with therapy (p < 0.001, d = 1.44), neither baseline nor change in neuromelanin-MRI signal associated with symptom improvement. Current results provide the first demonstration of the utility of neuromelanin-MRI in pediatric psychiatry, specifically highlighting in vivo evidence for midbrain dopamine alterations in treatment-seeking youth with OCD. Neuromelanin-MRI likely indexes accumulating alterations over time, herein, implicating dopamine hyperactivity in OCD. Given evidence of increased neuromelanin signal in pediatric OCD but negative association with symptom severity, additional work is needed to parse potential longitudinal or compensatory mechanisms. Future studies should explore the utility of neuromelanin-MRI biomarkers to identify early risk prior to onset, parse OCD subtypes or symptom heterogeneity, and explore prediction of pharmacotherapy response., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Altered brain response to errors in anxiety and obsessive-compulsive disorders (OCD) suggests cognitive control abnormalities across both types of illness, but behavioral metrics of cognitive control function have yet to be compared in patients selected from these different diagnostic categories. Thus, we examined post-error slowing (PES), a behavioral adjustment that typically occurs after a mistake, in children and adolescents with and without a primary anxiety disorder (N = 103 anxiety and N = 28 healthy controls) and adolescents and adults with and without OCD (N = 118 OCD and N = 60 healthy controls) using a go/no-go task. Primary analyses tested for differences in PES between diagnostic groups (anxiety, OCD, healthy), controlling for age, overall reaction time, and overall accuracy. Results indicated that patients with anxiety disorders exhibited more post-error slowing than both patients with OCD and healthy volunteers. In contrast, participants with OCD did not differ from healthy volunteers in post-error slowing. In subgroup analyses restricted to adolescent participants (ages 13-17 years), more post-error slowing was observed in the anxiety disorders group compared with either the OCD or healthy groups. These data suggest that excessive post-error slowing, an index of behavioral adjustment following errors, may uniquely characterize patients with anxiety disorders relative to healthy individuals and those with OCD., (© 2021. The Psychonomic Society, Inc.)