Plain-language summary of research published in the Georgian Medical Journal. Written for the general public by the GMJ News editorial team.
Parkinson’s disease is famous for what it does to dopamine — the brain chemical whose loss causes tremor, stiffness, and slowness. But dopamine is only part of the story. A study from the South Caucasus, published in the Georgian Medical Journal, turns the spotlight on a second neurotransmitter: serotonin.
What the Researchers Measured
The team conducted a case-control study measuring serum serotonin levels in Parkinson’s patients compared with healthy controls — and, critically, they stratified patients by motor phenotype (the dominant movement pattern of their disease) and by disease duration.
The Key Finding: A Duration-Dependent Decline
Serotonin levels were not simply lower in Parkinson’s patients — they declined progressively with disease duration. The longer a person had lived with Parkinson’s, the lower their serum serotonin. This pattern suggests that the serotonin system degenerates alongside the dopamine system as the disease advances, rather than being a fixed early abnormality.
Why Serotonin Matters in Parkinson’s
Serotonin influences mood, sleep, appetite, and pain perception — and depression, sleep disturbance, and fatigue are among the most disabling non-motor symptoms of Parkinson’s disease. A progressive serotonin decline offers a biological explanation for why these symptoms often worsen over time, and why they deserve treatment as seriously as tremor and rigidity.
Why It Matters
For clinicians, the finding supports monitoring and managing non-motor symptoms throughout the disease course. For researchers, serum serotonin emerges as a candidate biomarker of disease progression — potentially measurable with a simple blood test. And for the South Caucasus region, this study adds original neurological research from a population rarely represented in the international Parkinson’s literature.
Read the Original Research
Original article: Duration-dependent decline of serum serotonin in Parkinson’s disease: a motor-phenotype-stratified case-control study from the South Caucasus
Authors: Shorena Vashadze, Ketevan Saparidze, Mariam Kekenadze, Keso Gorgiladze et al.
Published in: Georgian Medical Journal, Vol. 1 No. 2 (2026) — Health Systems Performance and Quality of Care
DOI: 10.66636/gmj.v1.i2.a112
📄 Read the full article at gmj.ge →
Georgian Medical Journal (GMJ) · ISSN 3088-4322 · gmj.ge · Open Access CC BY 4.0 · Published by the Public Health Institute of Georgia (PHIG). This summary is an independent editorial product of GMJ News; for clinical decisions, consult the original peer-reviewed article and a qualified professional.
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