Vegetative symptoms and sexual well being are among the most serious non-motor symptoms in Parkinson disease (PD) patients. In the present study we evaluated symptom of diminished libido in patients with idiopathic PD and its relationship with depression severity. One-hundred fourteen consecutive PD patients (56 men; 49%) and 98 healthy controls (HC) (39 males; 40%) matched for age, educational level and gender, were evaluated during their phase of clinical and dopaminergic drug regimen stability. Sexual functioning was assessed using the Hamilton Depression Rating Scale item measuring diminished libido. Depression and anxiety severity were evaluated using the Beck Depression Inventory (BDI) and the Hamilton anxiety rating scale. Unipolar depression diagnosis was performed using the Structural Clinical Interview for DSM-IV (SCID-P).

Eighteen (18%) of the HC and 35 (31%) of the PD subjects showed clinically significant diminished libido and the difference in prevalence rate between the two groups was significant (chi-square=4.276; df=1; p=0.0387). An Analysis of Variance (ANOVA) showed that diminished libido was strongly associated with depression severity both in HC (F=44.013; df=1,208; p<0.0001) and in idiopathic PD (F=19.179; df=1,208; p<0.0001). No significant interaction effect between the two variables was present (F=0.074; df=1,208; p=0.786).

Diminished libido is present in a significant percentage of PD patients but this symptoms may be directly derived by the presence of unipolar depression. Future studies should ascertain if treatment of depression with antidepressant drugs may improve symptom of diminished libido in patients responding to the treatment.