Brain Scans Point to Dopamine Damage in Long COVID
A new brain imaging study led by scientists at the Centre for Addiction and Mental Health (CAMH) has found what researchers describe as the strongest evidence yet that long COVID is associated with damage to dopamine-releasing neurons in the brain. Published in eBioMedicine, the findings could help explain persistent fatigue-related loss of motivation, slower movement, and memory difficulties. They may also point toward new treatment strategies that target the brain's dopamine system.
Long COVID is estimated to affect about five per cent of the global population, including roughly two million people in Canada. The condition can involve a broad range of symptoms that continue for at least three months after the initial COVID-19 infection. Common brain-related symptoms include fatigue, brain fog, memory problems, and low mood. Despite how widespread and disruptive long COVID can be, there are currently no evidence-based treatments, in part because scientists still do not fully understand what is happening in the brain.
What the Study Examined
To investigate the biological roots of these symptoms, the CAMH-led team used positron emission tomography (PET), an imaging technique that can measure biological activity inside the brain. The researchers examined a well-established marker associated with the health and integrity of dopamine neurons in people with long COVID and compared the results with those from healthy participants.
Dopamine is a chemical messenger that plays a central role in motivation, movement, and cognitive function. The marker used in the study is not a direct count of dopamine neurons, but it offers a signal about the condition of dopamine nerve terminals. When levels of this marker are lower, it suggests a reduced density of dopamine nerve terminals.
Lower Marker Levels Across the Striatum
The researchers found substantially lower levels of the marker in people with long COVID across all major areas of the striatum. The striatum is a group of brain regions that helps regulate motivation, movement, and thinking. Because the striatum depends heavily on dopamine signaling, the widespread reduction is a notable finding. It suggests that long COVID may not be limited to one small brain area but may affect the dopamine system more broadly.
The study also found that different patterns of marker loss were associated with different symptoms. Lower levels in the ventral striatum were linked to greater loss of motivation. Reductions in the dorsal putamen were associated with slower movement, while lower levels in the caudate putamen were connected with memory difficulties.
Why the Striatum Matters
The striatum is often described as a hub for translating motivation into action. It helps people initiate movement, sustain effort, and process rewards. It also contributes to aspects of learning and memory. When dopamine signaling in this region is disrupted, the effects can reach far beyond movement alone.
That broad role may explain why the long COVID symptoms identified in the study overlap with functions supported by the striatum. Fatigue-related loss of motivation, slowed movement, and memory problems are all part of the symptom cluster that can make long COVID so disabling. The region-specific links found by the researchers add detail to the picture. They suggest that different parts of the striatum may contribute to different neurological symptoms.
Importantly, the study describes an association. It does not prove that COVID-19 directly causes the damage or that dopamine loss is the only factor behind long COVID fatigue and brain fog. The researchers describe the finding as a possible cause and the strongest evidence so far of a connection, which means the result is significant but not the final word.
Symptom Patterns Match Specific Brain Regions
The symptom-by-region pattern is one of the study's most striking features. Rather than finding a single uniform change, the researchers observed that lower marker levels in particular striatal areas tracked with particular complaints.
- Ventral striatum: Lower levels were linked to greater loss of motivation, a symptom that can make even simple tasks feel overwhelming.
- Dorsal putamen: Reductions were associated with slower movement, which may contribute to the physical sluggishness reported by some patients.
- Caudate putamen: Lower levels were connected with memory difficulties, a core feature of the cognitive fog that many people with long COVID describe.
These findings do not mean that every person with long COVID has the same brain changes. They do suggest, however, that the condition may have a measurable neurological signature in at least some patients. That signature could help researchers separate long COVID from other conditions that cause similar symptoms and could guide more targeted approaches to care.
The Global Burden of Long COVID
Long COVID is not a rare complication. It is estimated to affect about five per cent of the global population, and roughly two million people in Canada alone. The condition can involve a broad range of symptoms that persist for at least three months after the initial infection. Brain-related symptoms such as fatigue, brain fog, memory problems, and low mood are among the most common and most disruptive.
For many patients, these symptoms interfere with work, school, family life, and daily functioning. Yet there are currently no evidence-based treatments for long COVID. That gap has left clinicians and patients searching for explanations and options. A clearer understanding of the underlying biology is therefore a critical step toward better care.
A New Target for Treatment Research
The discovery could lead to new treatments that target the brain's dopamine system. While the study does not propose a specific therapy, it identifies a biological pathway that future research can explore. If dopamine neuron damage or dysfunction contributes to long COVID symptoms, then interventions aimed at protecting, restoring, or compensating for dopamine signaling might one day help.
That possibility is especially important because current treatment options are limited. Without evidence-based therapies, care for long COVID often focuses on managing symptoms rather than addressing root causes. By pointing to the dopamine system, the study offers a concrete direction for drug development and clinical trials.
The findings also highlight the value of brain imaging in understanding post-infectious illness. PET scans can reveal changes that are not visible on standard structural imaging. In this case, the technique allowed researchers to compare the health and integrity of dopamine neurons in people with long COVID against healthy participants. The result was a measurable difference across the striatum.
What the Findings Mean for Patients
For people living with long COVID, the study may offer more than a scientific explanation. It provides evidence that their symptoms are tied to measurable changes in the brain. Fatigue, brain fog, and low motivation are often invisible to others, and patients sometimes struggle to have their experiences recognized. A biological finding does not solve the problem, but it can help validate the reality of the condition and focus attention on the need for treatments.
The research also reinforces that long COVID is a complex condition with effects that extend beyond the lungs or the acute infection. The brain is clearly involved in at least some cases. Understanding how the virus or the immune response affects dopamine neurons could shed light on other post-viral syndromes as well, though the current study focuses specifically on long COVID.
Key Takeaways
- A CAMH-led PET imaging study found substantially lower levels of a marker linked to dopamine neuron health in people with long COVID.
- The reductions appeared across all major areas of the striatum, a brain region involved in motivation, movement, and thinking.
- Different patterns of marker loss were associated with different symptoms: ventral striatum with loss of motivation, dorsal putamen with slower movement, and caudate putamen with memory difficulties.
- Long COVID affects about five per cent of the global population and roughly two million people in Canada, yet there are no evidence-based treatments.
- The findings, published in eBioMedicine, could lead to new therapies that target the brain's dopamine system.
The study adds an important piece to the long COVID puzzle. It does not answer every question, but it points researchers toward the dopamine system as a promising area for future investigation. For patients, that direction offers hope that the invisible symptoms of long COVID may eventually have visible, treatable causes.
This article is based on reporting by Science Daily. Read the original article.
Originally published on sciencedaily.com
