The most common diagnosis was anxiety, found in 17% of those treated for Covid-19, followed by mood disorders, found in 14% of patients.
And while the neurological effects are more severe in hospitalized patients, they are still very common in those who were only treated on an outpatient basis, the researchers note.
“That percentage gradually increased as the severity of Covid-19 disease increased. Looking at patients admitted to the hospital, that percentage increased to 39%,” said Maxime Taquet, an academic clinical fellow in psychiatry. at the University of Oxford, and a co-author of the new study.
The results help light the way for how the health care system should continue to help Covid-19 survivors, the researchers said.
“Our results indicate that brain and psychiatric disorders are more common after Covid-19 than after influenza or other respiratory infections, even when patients are matched for other risk factors. We now need to see what happens after six months,” added Taquet.
Covid-19 as a ‘brain disease’
It is the largest study of its kind to date and involved the electronic health records of more than 236,000 Covid-19 patients, mainly in the US. The researchers compared their data with those who had experienced other respiratory infections in the same time frame.
They noted that those with Covid-19 had a 44% increased risk of neurological and psychiatric illness compared to those recovering from the flu. And they were 16% more likely to experience those effects compared to people with other respiratory infections.
About one in 50 Covid-19 patients had an ischemic stroke, a blood clot that affects the brain.
However, Covid-19 did not necessarily increase the risk for the full spectrum of neurological disorders.
“Two major negative findings were related to Parkinsonism and Guillain-Barré syndrome,” said Taquet. “Both conditions are neurological conditions that we know are sometimes associated with viral infection. We did not find that they were more common after Covid-19 and the other respiratory tract infections we looked at.”
The study was important in part because of the sheer number of patient records the researchers were able to analyze, said Dr. Musa Sami, a clinical associate professor of psychiatry at the University of Nottingham.
“This is a robust piece of work in a large cohort demonstrating the association between Covid-19 and psychiatric and neurological complications,” he said in a statement. “This is a very important topic as there is considerable consternation about Covid-19 as a ‘brain disease’.”
Sami, who was not involved in the study, stressed the need for further research into how exactly Covid-19 affects the brain and nervous system. “Psychological stress, longer hospital stays and features of the disease itself may play a role,” he said.
One clue: Psychological symptoms are more common than serious neurological complications, according to Masud Husain, a professor of neurology and cognitive science at the University of Oxford and co-author of the study.
“It is really the people with very serious illness who are at greater risk of developing the neurological complications, contrary to what we see with the mental health complications, which are much more serious across the board,” he said.
The longer-term burden of Covid-19 on the health system
One limitation of the Lancet Psychiatry study is that it uses “routine health data” rather than research data, said Paul Harrison, a professor of psychiatry at the University of Oxford and the study’s lead author.
This could mean that diagnoses are missing, not fully investigated, or incorrect.
And the diagnosis alone can make a difference.
“Patients who had Covid-1919 are more likely to receive a neurological and psychiatric diagnosis simply because they received more follow-up and more medical attention compared to patients with respiratory infections. The rates have seen,” Taquet said in a newsletter.
Yet the study provides a comprehensive picture of the long-term burden the pandemic will have on those it affected.
“While the individual risks are small for most conditions, the impact across the population could be significant for health and social care systems because of the scale of the pandemic and the fact that many of these conditions are chronic,” said Harrison. “As a result, healthcare systems must be provided with resources to meet anticipated needs, both within primary and secondary care.”