The relationship of serotonin transporter (SERT) availability and age of onset in untreated patients with obsessive-compulsive disorder (OCD)

Objectives Differences of the results of brain SERT studies in OCD might be due to distinct phenotypes, i.e. the age of onset. We investigate SERT availability with PET and C-11-DASB in relation to the age of onset.

Methods Seventeen untreated OCD patients (37±9yrs, 8 females) and 11 age-and gender-matched healthy controls (HC) underwent dynamic PET after IV injection of 570 MBq C-11-DASB. Distribution volume ratios (DVR) images were generated using MRTM2 (Ichise et al. 2003). VOI analysis was performed after co-registration of the DVR maps with individual MRI. Severity of OCD was rated by the Yale-Brown Obsessive Compulsive Scale (YBOCS).

Results Age had a significant effect on DVR across the brain regions in patients (r=-0.713, p=0.001 in the insula, r=-0.473, p=0.055 in the left dorsolateral frontal/DLF cortex) but not in HC. There was a negative relationship between DVR and age of onset (e.g. left thalamus r=-0.467, p=0.044, age-corrected) with significant lower values in the LO-OCD compared with EO-OCD. DVR of EO-OCD patients did not differ from HC. Lower than normal DVR were found in LO-OCD in any brain region (p=0.003 in the hippocampus/amygdale, p<0.001 in the striatum and the thalamus). YBOCS and DVR were correlated in the right DLF (r=0.504, p=0.028) and the left medial frontal cortex (0.473, 0.041).

Conclusions Late but not early onset of OCD is associated with abnormal low SERT availability. With increasing age, SERT availability showed a pronounced decline in OCD compared with HC.