Distinct resting state functional connectivity abnormalities in hoarding disorder and major depressive disorder.

Emerging research suggests that hoarding disorder (HD) is associated with abnormal hemodynamic activity in frontal brain regions. Prior studies have not examined intrinsic network connectivity in HD during unstructured "resting state" fMRI. Furthermore, it remains unclear whether previously observed HD abnormalities might be better explained by the presence of other disorders frequently comorbid with HD, such as major depressive disorder (MDD). The current study compared resting state functional connectivity in HD-only patients (n = 17), MDD-only patients (n = 8), patients with co-occurring HD and MDD (n = 10), and healthy control participants (n = 18). Using independent component analysis, we found that HD-only patients exhibited lower functional connectivity in a "task positive" cognitive control network, compared to the other three groups. The HD group also had greater connectivity in regions of the "task negative" default mode network than did the other groups. Findings suggest that HD is associated with a unique neurobiological profile, and are discussed in terms of recent neurological and neuropsychological findings and models in HD and related disorders.