Abstract

Parkinson's disease (PD) is classically considered a motor disease; however, several non-motor symptoms are also present, including psychiatric complaints. In recent decades, the metals Ca, Fe, and Zn have gained prominence as potential etiologic factors in motoric signs of PD. However, metal alterations could be associated with the non-motor symptoms of PD. We wished to correlate the levels of these metals with the co-occurrence of depression, anxiety, and psychotic symptoms in PD patients. To this end, the Beck Depression Inventory, the Beck Anxiety Inventory, and the Scales for Outcomes in Parkinson's disease-Psychiatric Complications (SCOPA-PC) were implemented to evaluate mood disorders and psychiatric complications. Flame atomic absorption spectrometry (FAAS) was used to assess concentrations of Ca, Fe, and Zn in hair samples collected from 22 clinically diagnosed PD patients, which represented the entire cohort of accessible patients in a Brazilian health registry, and 33 healthy individuals. While Ca and Fe alterations were not found to be associated with psychiatric complaints in the PD group, significantly higher levels of Zn were correlated in PD patients with depression and some psychotic symptoms. Within individual domains of the SCOPA-PC, significantly higher levels of Zn were correlated with the presence of hallucination, illusion, and paranoid ideation when compared to controls and PD patients who did not present these symptoms. Although our sample size is small and findings need to be replicated in larger and heterogeneous populations, our results provide a new perspective on the use of monitoring of Zn levels as a potential biomarker of psychiatric complaints, and may be useful in the development of more effective therapeutic approaches for the management of PD patients with co-occurrence of psychiatric disorders.