Cause or Effect? A Review of Evidence from the Past Two Decades Analyzing the Impact of Gut Dysbiosis on Parkinson’s Disease

The relationship between gut dysbiosis and Parkinson's disease has emerged as a focal point of scientific inquiries in the early 21st century due to a proliferation in knowledge surrounding the role of the gut-brain axis in neurological disorders.Over the last two decades in particular, evidence has suggested that the gut microbiota's release of pro-inflammatory cytokines, formation of alpha-synuclein, and decreased production of short-chain fatty acids (SCFAs)-whilst in a state of dysbiosis-have detrimental impacts on brain health, leading to profuse issues such as blood-brain barrier (BBB) permeability which catalyze Parkinson's disease.While many adopt this viewpoint, this topic remains contentious as numerous gut microbial researchers disagree with the notion that dysbiosis governs the disease, viewing it more as a consequence of Parkinson's ability to reduce motor integrity and alter lifestyle habits.This review aims to provide a nuanced resolution to the prevailing debate, analyzing research over the last 20 years to see whether the gut microbiota primarily causes Parkinson's disease or is just an effect of its modes of action.