Study Finds Dopamine System Damage in Long COVID Patients’ Brains

A groundbreaking brain imaging study conducted by the Centre for Addiction and Mental Health (CAMH) has unveiled compelling evidence linking long COVID symptoms to injury of dopamine-releasing neurons in the brain. Published in eBioMedicine, the research leverages positron emission tomography (PET) to reveal a significant reduction of dopamine transporter markers in key striatal regions, potentially accounting for hallmark long COVID symptoms such as fatigue, cognitive impairment, and motor slowing.

Long COVID affects approximately five percent of the global population, manifesting as a constellation of persistent symptoms—many neurological—lasting months beyond the initial SARS-CoV-2 infection. Until now, the pathophysiological mechanisms underlying these chronic neuropsychiatric symptoms remained poorly understood, hindering therapeutic development. This study marks a pivotal advance by characterizing clear dopaminergic neuronal injury in affected individuals.

Dopamine neurons, crucial for motivation, movement, and cognition, predominantly reside in the striatum, a deep brain region. Using PET imaging with a highly specific marker for vesicular monoamine transporter 2 (VMAT2), the researchers quantified dopamine neuron integrity in long COVID patients versus healthy controls. The findings revealed reduced VMAT2 binding across the striatum’s ventral and dorsal components, correlating tightly with clinical symptom severity. Depletion in the ventral striatum aligned with diminished motivation, while loss in the dorsal putamen corresponded to bradykinesia, and reductions in the caudate putamen mirrored memory deficits.

Dr. Jeffrey Meyer, senior author and senior scientist at CAMH’s Brain Health Imaging Centre, emphasized that this is the strongest evidence to date implicating dopaminergic neurodegeneration in long COVID. Such neuronal loss has been extensively documented in other neurological disorders associated with overlapping symptoms, providing a pathophysiological framework for understanding the enduring neurological impairments reported by long COVID patients.

This research builds decisively on previous findings by the same group demonstrating elevated neuroinflammation within dopaminergic brain regions in long COVID. Inflammation is known to mediate dopamine neuron injury, and this study’s direct evidence of reduced dopamine transporter density offers a mechanistic link tying inflammation to neuronal dysfunction and symptomatology.

The implications for treatment are profound. Current long COVID therapeutic strategies largely neglect the dopaminergic system, focusing instead on inflammation and immune modulation. The CAMH team suggests that repurposing drugs aimed at boosting dopamine neurotransmission—such as dopamine precursors or inhibitors of dopamine metabolism—could represent a rational and promising intervention strategy.

Importantly, the study sets the stage for clinical trials to test dopamine-targeted therapies in long COVID. With collaboration from the University Health Network, trials will soon explore whether enhancing dopamine signaling can alleviate long COVID’s neuropsychiatric sequelae including fatigue, memory impairment, and motivational deficits.

For millions suffering worldwide, these findings offer both validation and hope—affirming that their symptoms have a biological basis and opening new avenues for evidence-based treatments. As research progresses, understanding the dopaminergic basis of long COVID may reshape how this multifaceted syndrome is approached clinically and scientifically.