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 inpatients, they are still common in those who were only treated outpatient, the researchers note.
“This rate increased gradually as the severity of Covid-19 disease increased. If we look at patients who were admitted, it increased to 39%,”
The results help shed light on how the health care system should continue to help Covid-19 survivors, the researchers said.
“Our results indicate that brain diseases and psychiatric disorders are more common after Covid-19 than after influenza or other respiratory infections, even when patients are matched with other risk factors. We now need to see what happens beyond six months,” Taquet added.
Covid-19 as a ‘brain disease’
It is the largest study of its kind yet and involved the electronic health records of more than 236,000 Covid-19 patients, mostly in the United States. The researchers compared their records with those who experienced other respiratory infections in the same time frame.
They observed that those with Covid-19 had a 44% increased risk of neurological and psychiatric illness compared to people returning from influenza. And they were 16% more likely to experience these effects compared to people with other respiratory infections.
Approximately one in 50 Covid-19 patients had an ischemic stroke, which is a blood clot that affects the brain.
However, Covid-19 did not necessarily increase the risk of the full range of neurological diseases.
“Two important negative findings were related to parkinsonism and Guillain-Barré syndrome,” Taquet said. “Both of these conditions are neurological conditions that we know are sometimes associated with viral infection. We did not find them to be more common after Covid-19 and after the other respiratory infections we looked at.”
The study was important in part because of the large number of patient records that the researchers were able to analyze, according to 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 showing the link between Covid-19 and psychiatric and neurological complications,” he said in a statement. “This is a very important issue as there has been considerable concern about Covid-19 as a ‘brain disease’. “”
Sami, who was not associated with the study, stressed the need for further study of how Covid-19 exactly affects the brain and nervous system. “Psychological stress, longer stays in the hospital and characteristics of the disease itself can play a role,” he said.
One clue: psychological symptoms are more common than serious neurological complications, according to Masud Husain, professor of neurology and cognitive science at the University of Oxford, and a co-author of the study.
“It is really the people with very serious illness who are at greater risk of developing the neurological complications, as opposed to what we see with the mental complications, which are much more across the board with severity,” he said.
Covid-19’s long-term burden on the health system
One limitation of the Lancet Psychiatry study is that it uses “routine health data” rather than research data, according to Paul Harrison, a professor of psychiatry at the University of Oxford, and the study’s lead author.
This may mean that diagnoses are missing, they have not been fully investigated, or that they are incorrect.
And just being diagnosed can make a difference.
“Patients who had Covid-1919 could be more likely to get a neurological and psychiatric diagnosis, simply because they received more follow-up, more medical care compared to patients with respiratory infections. This may explain some of the differences we have observed in the rates, ”Taquet told a news briefing.
But still, the study provides a wonderful overview of the long-term burden that the pandemic will have for those affected.
“Although the individual risks for most disorders are small, the impact across the entire population can be significant for health and social care systems due to the scale of the pandemic and the fact that many of these conditions are chronic,” Harrison said. “As a result, healthcare systems must have the resources to meet the expected needs, both in primary and secondary care services.”