Mild affective symptoms in de novo Parkinson's disease patients: relationship with dopaminergic dysfunction

Background and purpose: The investigation of the relationship between affective symptoms and dopamine transporter (DAT) density provided conflicting data in both Parkinson's disease (PD) and non-PD patients. However, the potential interference of psychoactive as well as anti-parkinsonian drugs on DAT density should be taken into account. Objective: To investigate the relationship between affective symptoms and presynaptic dopaminergic function in de novo PD patients. Methods: Forty-four de novo PD consecutive outpatients were recruited, and the severity of anxious symptoms was evaluated with the Hamilton Anxiety Rating Scale (HAM-A), the severity of depressive symptoms with the Hamilton Depression Scale (HAM-D) and the Beck Depression Inventory (BDI). Six patients had a formal diagnosis of depression. All patients performed I-123-FP-CIT SPECT, and semi-quantitative striatal indices were calculated. Results: Disease severity, as measured by Unified Parkinson's Disease Rating Scale (UPDRSIII), was inversely correlated with bilateral striatal indices. Bilateral striatal uptake was significantly positively correlated with HAM-D (r.329; r.423, respectively, right and left), BDI (r.377; r.360, respectively, right and left) and HAM-A (r.338; r.340, respectively, right and left). After controlling for age, disease duration and severity, and Mini Mental State Examination (MMSE), no significant reduction in r-values was observed (P < 0.05). Conclusion: Our data support the existence of a relationship between depressive and anxious symptoms and the striatal I-123-FP-CIT uptake. The finding of an increased DAT density associated with mild affective symptoms could be due to the lack of compensatory mechanisms usually present in early PD, and/or it might have a pathogenic role in affective symptoms by reducing the dopaminergic tone in the synaptic cleft.