Abstract
Introduction: Early-onset obsessive-compulsive disorder (EOCD) and late-onset obsessive-compulsive disorder (LOCD) are distinct subtypes of obsessive-compulsive disorder. EOCD patients respond poorer to pharmacotherapy with serotonin reuptake inhibitors (SRIs) blocking serotonin transporters (SERTs). Still, there has been no study investigating two subgroups who are under pharmacotherapy. The aim of this study was to compare SERT binding potentials (BPs) using [11C]DASB PET in EOCD and LOCD patients currently taking escitalopram.
Methods: Six EOCD patients whose age of onset was <17 years and six LOCD patients whose age of onset ≥17 years were enrolled. They underwent serial PET scans during maintenance therapy with escitalopram and their plasma concentration of escitalopram was measured simultaneously with the scan. Drug-free BPs were obtained from an Emax modelling we previously developed.
Results: SERT availability was significantly different between subgroups in putamen (t=2.386, p=0.038), but not in caudate nucleus (t=0.740, p=0.476), thalamus (t=0.019, p=0.985), and dorsal raphe nucleus (t=1.658, p=0.128). Drug-free BPs of putamen had a negative correlation (r=-0.580, p=0.048) with age of onset of the disease, but not with the YBOCS scores.
Conclusions: SERT availability was higher in putamen of EOCD patients than LOCD, and negatively correlated to the age of onset, in putamen of OCD patients. The finding suggests less extent of serotonergic pathology in younger EOCD patients even after long-term pharmacotherapy and that the non-SRI therapies would be a better option for them.