For years, long COVID patients have described debilitating neurological symptoms — brain fog, apathy, memory loss, slowed movement — with little scientific explanation and no proven treatments. A new study published in eBioMedicine may finally offer some answers, pointing to measurable damage in the brain's dopamine system as a key culprit.

Researchers at Toronto's Brain Health Imaging Centre used PET brain imaging to measure vesicular monoamine transporter 2 (VMAT2) — a marker of dopamine neuron integrity — in 24 adults with long COVID and 24 healthy controls. They found significantly reduced VMAT2 levels across all major regions of the striatum in long COVID patients, suggesting a real loss of dopamine-releasing nerve terminals. Crucially, the pattern of loss matched patients' symptoms by brain region.

The findings open a promising new treatment avenue: existing medications that boost dopamine function — including dopamine precursors and inhibitors of dopamine metabolism — could potentially be repurposed for long COVID. A clinical trial targeting dopamine function is planned in collaboration with University Health Network.

By the Numbers

• 16–20% lower VMAT2 levels in long COVID patients vs. healthy controls across striatal regions
• 5% of the global population estimated to be affected by long COVID
• 24 long COVID patients and 24 healthy controls in the primary analysis (extended to 43 controls for exploratory analyses)
• Lower ventral striatum binding → reduced motivation; lower dorsal putamen binding → slowed movement; lower caudate binding → memory difficulties

Why it matters: This study shifts long COVID brain research from symptom description to measurable biology, giving clinicians a potential mechanism to target — and patients a biological validation of their very real struggles.