Spontaneous activity and functional connectivity in patients with hoarding disorder comorbid with attention-deficit/hyperactive disorder

Despite recent studies suggesting an important association of hoarder disorder (HD) and attention-deficit/hyperactive disorder (ADHD), no neuroimaging study has investigated the differences between patients with HD comorbid with ADHD and those without ADHD. This study investigated the regional spontaneous activity and functional connectivity in HD, focusing on the comorbidity with ADHD. Resting-state functional magnetic resonance imaging (MRI) data were obtained from 24 patients with HD and 31 healthy individuals. We investigated the group differences using the fractional amplitude of low-frequency fluctuation (fALFF). The altered regions in the fALFF were used as seeds in a functional connectivity analysis where we conducted group comparisons among the three groups: healthy controls (HCs), HD with ADHD (HD +ADHD), and HD without ADHD (HD -ADHD). Compared to HCs, patients with HD had a reduced fALFF in the right inferior frontal gyrus (IFG). Functional connectivity analysis revealed that patients with HD + ADHD had reduced functional connectivity between the IFG and dorsolateral prefrontal cortex (DLPFC) compared to HCs, while the HD -ADHD group was intermediate level between HD +ADHD and HCs groups. In conclusion, patients with HD have altered spontaneous activity of the IFG. Additionally, patients with HD + ADHD had significantly reduced functional connectivity between the IFG and the DLPFC. Our findings suggest the potential need to distinguish between subgroups of HD+ADHD to identify novel neurobiological models of HD that could guide future therapeutic strategies.