If you find yourself extra irritable or feeling sad after recovering from Covid, there may be a biological reason.
Scientists have found the virus can infect brain cells responsible for mood, stress and movement, which could stop them from functioning properly.
Lab experiments using human cells showed Covid damages dopamine production, deteriorating cells to the point they can’t grow and divide.
Dopamine – dubbed the happy hormone – is also responsible for sleep, concentration, movement learning and memory, so the finding would explain why Covid causes symptoms such as brain fog and the blues.
Damage to dopamine neurons can cause fatigue, lack of concentration, moodiness and anxiety, depression , loss of interest and pleasure in experiences and trouble sleeping.
For the study, a team from Weill Cornell Medicine, Columbia University and Memorial Sloan Kettering Cancer Center used human stem cells to generate multiple types of cells found in the human body to see how the Covid virus affected each.
Researchers used the lab-grown cells and confirmed their findings with autopsy samples from people infected with Covid.
The study showed it was only dopamine neurons that became infected with SARS-CoV-2, which caused them to stop working and send out chemical signals that cause inflammation.
Researchers said the results of their study were unexpected as they initially set out to discover how Covid affects multiple cells, but only found this impact on dopamine neurons.
Senior author Dr Shuibing Chen of Weill Cornell Medicine said: ‘This project started out to investigate how various types of cells in different organs respond to SARS-CoV-2 infection. We tested lung cells, heart cells, pancreatic beta cells, but the senescence pathway is only activated in dopamine neurons.
‘This was a completely unexpected result.’
Senescence, or biological aging, is the gradual deterioration of function in living organisms.
It results in the inability of healthy cells to grow and divide.
Wrinkles, worsening eyesight and loss of hearing as people age are all examples of normal senescence.
The process also leads to stem cell damage and chronic inflammation.
Dr Chen added: ‘The infection rate of dopamine neurons isn’t as high as lung cells, the virus’s main target, but even a small population of infected cells can potentially have a severe effect.’
The researchers suggest these findings may shed light on the neurological symptoms people suffering from long Covid experience.
The study found approximately five percent of dopamine neurons can be infected by the Covid virus, leading to senescence and inflammation.
However, the team also found three medications – riluzole, metformin, and imatinib – could potentially protect against the Covid virus from infecting dopamine neurons.
Riluzole is a drug used to treat Lou Gehrig’s Disease. Metformin can be used to treat diabetes and imatinub is used to treat leukemia and other types of cancer.
The scientists said further research into these drugs, which are all approved by the Food and Drug Administration, may lead to a way to prevent Covid’s attack on the brain.
Researchers stressed while most people may be exposed to Covid, not all are susceptible to dopamine neuron damage.
There are a number of factors involved in the neurological risk, including genetics and severity of the disease.
They recommend larger human population studies to explore this issue more.
Additionally, because dopamine neuron senescence is a hallmark of Parkinson’s disease, the researchers recommend people suffering from long Covid be monitored for an increased risk of developing Parkinson’s-related symptoms
The study was published in Cell Stem Cell.