Neurodegeneration in Parkinson’s Disease Linked to Depression, Psychosis, Study Suggests

Eric Taipale
2 min readNov 22, 2021
Photo by Robina Weermeijer on Unsplash

A study published in the American Journal of Geriatric Psychiatry entitled ‘Brainstem Pathologies Correlate With Depression and Psychosis in Parkinson’s Disease’ has concluded the existence of a possible link between the neuronal loss and gliosis associated with the symptomatic characteristics of Parkinson’s Disease (PD) with psychosis and depression.

Nicole Mercado Fischer, MPH of Johns Hopkins University, Baltimore and her colleagues who had oriented this study affirmed the importance of their research, describing the lack of research concerning the impact of Lewy bodies in Parkinson’s Disease and the link between the associated neurodegeneration with depression and psychosis.

The researchers analyzed the brains of 175 individuals with primary pathologic diagnosis of PD and semi-quantitatively measured the burden of gliosis, Lewy body pathology, and neuronal loss within two parts of the brain; the locus coeruleus (LC), located in the brain stem, and the substantia nigra (SN), located in the midbrain. Among the participants, the average age of onset of Parkinson’s Disease was 62.4 years; 97.8 percent were white; 67.4% of the individuals were male, and the mean duration of illness was 16 years.

The researchers established that of 175 individuals; 55 had anxiety, 98 had psychosis, and 88 had depression. Additionally, it was concluded that there was a significant association between psychosis and severe neuronal loss and the presence of gliosis in the locus coeruleus and substantia nigra. Depression was also significantly associated with severe neuronal loss in the substantia nigra, however, not in the locus coeruleus. The research also yielded important information relating to the connection between anxiety and neuronal loss; in which there was no link.

It was also concluded that “psychosis and depression in Parkinson’s disease are associated with the underlying neurodegenerative process and demonstrate that cell loss and gliosis may be a better marker of neuropsychiatric symptoms than Lewy body pathology.”

Furthermore, the researchers noted that they were limited by seven factors — namely the retrospective design and incapability to accumulate pathology data for all individuals. Although, the large sample size reinforced the results.