According to positron emission tomography scans published in eBioMedicine by researchers at the Centre for Addiction and Mental Health, long COVID is associated with measurable injury to dopamine-releasing neurons in brain regions that regulate motivation, movement, and memory. The findings provide a potential biological explanation for persistent neurological symptoms affecting an estimated five percent of the global population.
PET Scans Reveal Dopamine Neuron Loss in Long COVID Patients
Researchers used positron emission tomography, an imaging technique that measures biological activity inside the living brain, to examine a marker of dopamine neuron integrity. According to the study, participants with long COVID showed substantially lower levels of this marker across all major areas of the striatum when compared with healthy control participants.
This reduction points to a lower density of dopamine nerve terminals in brain regions responsible for motivation, movement, and thinking. “Our findings provide compelling evidence that long COVID involves the loss of dopamine-releasing neurons,” says Dr. Jeffrey Meyer, senior author of the study, senior scientist at the Brain Health Imaging Centre, and Canada Research Chair.
Symptom Patterns Match Specific Brain Region Deficits
Different patterns of marker loss mapped directly onto specific clinical symptoms experienced by patients, according to study data. Lower levels in the ventral striatum were linked to a greater loss of motivation, while reductions in the dorsal putamen correlated with slower movement.
Additionally, lower marker levels in the caudate putamen were connected with memory difficulties. “This kind of injury is well known to produce symptoms like lack of motivation and motor slowing, and may contribute to memory difficulties in other neurological conditions,” Dr. Meyer explains.
Did You Know? Long COVID is estimated to affect approximately nine million adults in the United States and about 5% of the population worldwide, making it one of the most common chronic conditions emerging from the pandemic.
Connection Between Brain Inflammation and Dopamine Damage
The new imaging results build on previous work by the same research team at the Centre for Addiction and Mental Health, which found unusually high levels of inflammation in the brains of people with long COVID. That inflammation was especially pronounced in regions rich in dopamine-producing neurons.
“We know that inflammation can injure dopamine neurons,” notes Dr. Meyer. While the earlier research documented high inflammation levels in those areas, the latest study provides direct evidence that the dopamine neuron marker is reduced in those exact regions and correlates directly with patient symptoms.
New Directions for Clinical Trials and Treatments
The findings could shift how the medical community approaches long COVID treatment. Very few clinical trials have focused directly on dopamine-releasing neurons, as most previous research centered on general brain inflammation and immune activity.
“These results indicate that long COVID is, at least in part, a disorder of the brain’s dopamine system,” Dr. Meyer states. The study suggests that repurposing medications that augment dopamine function, such as dopamine precursors and inhibitors of dopamine metabolism, could represent a promising therapeutic strategy.
Susan Deuville, a lived experience research advisor to Dr. Meyer who contracted COVID-19 in 2021, notes that the findings offer validation. “For five years I have been seeking answers on what happened to me,” Deuville says. “It was a crushing loss of the life I had and the person I was before. The research of Dr. Meyer brings hope.”
Building on these results, researchers plan to launch a clinical trial in the upcoming couple of months in collaboration with the University Health Network. The trial will evaluate whether modifying dopamine activity can improve memory, motivation, and fatigue in long COVID patients. The underlying work was supported by the Canadian Institutes of Health Research.
Frequently Asked Questions
What is long COVID?
Long COVID is a chronic condition characterized by symptoms such as fatigue, brain fog, memory difficulties, and mood changes that continue for at least three months after an initial SARS-CoV-2 infection.
How did researchers discover dopamine damage in long COVID?
Researchers used positron emission tomography (PET) scans to measure a marker of dopamine neuron health in the striatum, comparing individuals with long COVID against healthy control participants.
Are there approved treatments for long COVID dopamine damage?
No evidence-based treatments are currently approved, but researchers plan to launch clinical trials to test whether repurposing medications that augment dopamine function can improve patient symptoms.