High Levels of Zinc Found in Hair of Parkinson’s Patients with Depression, Psychiatric Symptoms, Study Says

Parkinson’s disease patients with either depression or psychiatric symptoms such as hallucinations, confusion, or illusion may have higher levels of the mineral zinc in their hair, researchers report.

Their study, “Higher zinc concentrations in hair of Parkinson’s disease are associated with psychotic complications and depression,” was published in the Journal of Neural Transmission.

Besides the typical motor symptoms, Parkinson’s patients may also experience non-motor symptoms such as cognitive impairment, sleep difficulties, depression, anxiety, and psychosis. Psychosis, although not fully understood, is common in Parkinson’s, particularly in its later stages. Symptoms include minor illusions, vivid dreams, occasional visual hallucinations, paranoia, and panic attacks.

Evidence indicates an imbalance of metal compounds is somewhat associated with Parkinson’s disease mechanism. In fact, too much iron has been found within patients’ substantia nigra and striatum — two brain regions involved in motor control that are extensively damaged in Parkinson’s — as well as in other peripheral tissues.

In this neurodegenerative disorder, calcium has also been suggested to play a role by promoting cellular death, while zinc may influence non-motor features of the disease.

These minerals are strongly correlated to psychiatric complaints and mood disorders in Parkinson’s, but the exact relationship between calcium, iron, and zinc levels in Parkinson’s patients with psychiatric complaints remains to be clarified.

Therefore, researchers at the University of Copenhagen in Denmark, along with collaborators in Brazil and Ireland, set out to investigate the link between these metal compounds and the co-occurrence of depression, anxiety, and psychotic symptoms in Parkinson’s disease.

Twenty-two patients (15 men and seven women, with a mean age of 69.8 years), who were registered in the 13th Regional Health Board in Jequié, Bahia (Brazil), had their mood and psychiatric complications assessed by clinically validated scales. Using the participants’ hair samples, scientists also quantified calcium, iron, and zinc levels.

To do so, the investigators applied a technique called flame atomic absorption spectroscopy (FAAS), which uses the absorption of electromagnetic radiation to measure the concentration of gas-phase atoms. The results were compared to 33 healthy individuals.

Significantly higher zinc levels were found to be correlated with depression or with one or more psychotic complications, including hallucinations, illusion, paranoid ideation (when the patient believes he or she is being harassed or persecuted), altered dream phenomenon, and confusion, compared with patients without these symptoms and healthy controls.

Altered concentrations of calcium and iron were not associated with Parkinson’s-related psychiatric disturbances.

Although the sample size was small, the study seemed to suggest that zinc levels could be a biomarker for psychiatric manifestations in Parkinson’s, and as such, a potential target for novel disease management therapies.

“FAAS is simple to implement, and low in cost, and as it can be used with a biological sample easy to obtain, such as hair, this methodology offers the real advantage of being feasible for a wide range of clinics to implement,” the team said, adding that further research and larger studies are still warranted.