Mild cognitive or depressive symptoms are common in Parkinson disease (PD) and may represent a prestage for dementia or depression.^1-3 Patients with PD with cognitive and depressive symptoms are at higher risk of developing clinically manifest dementia or depression.^1-3 Mild cognitive or depressive symptoms in PD that do not fulfill the DSM-IV criteria for dementia or depression can be defined by performing validated neuropsychological screening scales using the Mini-Mental State Examination (MMSE)⁴ or DemTect⁵ scale and the Beck Depression Inventory (BDI),^6,7 respectively.

The pathogenetic role of central serotonin transporters (SERT) in obsessive–compulsive disorder (OCD) has been investigated in vivo by positron emissi