• A study suggests that in the United States in 2020, around a third of COVID-19 survivors were diagnosed with a neurological or mental health condition within 6 months of their COVID-19 diagnoses.
• Anxiety and mood disorders were the most common diagnoses.
• Neurological conditions, such as stroke and dementia, occurred less often but were more common among people with severe COVID-19.
• The overall effect of these disorders, many of which are chronic, may be substantial for health and social care systems due to the scale of the pandemic.

From the start of the COVID-19 pandemic, there have been concerns that survivors may have an increased risk of neurological and mental health conditions.

Initially, these concerns were based on past experience with other coronaviruses, but suspected cases linked with COVID-19 soon followed.

There was also early evidence that the illness can affect the central nervous system.

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In November 2020, an observational study from scientists at the University of Oxford, in the United Kingdom, reported that survivors had a greater risk of developing mood and anxiety disorders in the 3 months after receiving a COVID-19 diagnosis.

The same researchers have now used the health records of more than 236,000 patients in the U.S. to estimate the risks of developing neurological and psychiatric conditions in the 6 months after a COVID-19 diagnosis.

Participants had received COVID-19 diagnoses between January 20 and December 13, 2020.

The researchers estimate that the overall incidence of neurological or mental health diagnoses was 34%.

In the 6 months after their COVID-19 diagnoses, 13% of the participants received their first diagnosis of a neurological or psychiatric condition.

The most common diagnoses were anxiety disorders, in 17% of all the participants, mood disorders, in 14%, substance misuse disorders, in 7%, and insomnia, in 5%.

The incidence of neurological disorders was lower — 2.1% of all the participants experienced an ischemic stroke, 0.7% developed dementia, and 0.6% developed a brain hemorrhage.

This new study has been published in The Lancet Psychiatry.

Links with disease severity

Those who experienced more severe COVID-19 had a greater risk of mental health and neurological diagnoses.

Participants who experienced delirium, which is a sudden state of confusion, or encephalopathy, which is brain disease or damage, during their illnesses had the highest overall risk, at 62%, during the following 6 months.

Prof. Paul Harrison, the senior author of the study, says that the results confirm the high rates of mental health diagnoses after COVID-19.

He emphasized that while the incidence of neurological disorders was much lower than that of mental health conditions, this risk was still significant, particularly among people with severe COVID-19.

Prof. Harrison believes that resources to cope with the extra demands on primary and secondary care services should be provided.

“Although the individual risks for most disorders are small, the effect across the whole population may be substantial for health and social care systems due to the scale of the pandemic, and […] many of these conditions are chronic,” he adds.

Respiratory infection comparison

The researchers analyzed data from the health records of 236,379 people with diagnosed COVID-19 in the TriNetX database.

They compared outcomes for this group with those of 105,579 people with influenza and 236,038 people with any respiratory tract infection diagnosed between January and December 2020. The latter two groups acted as controls.

To account for underlying health risks, the team matched the people in each group in terms of characteristics such as age, sex, ethnicity, and other ongoing health conditions.

The odds of having a diagnosis of a neurological or mental health condition were 44% higher after COVID-19 than after the flu. These odds were 16% higher after COVID-19 than after another respiratory tract infection.

Meanwhile, there was no clear evidence of more diagnoses of Parkinsonism or Guillain-Barré syndrome after COVID-19 than after the flu or other respiratory tract infections.

“We now need to see what happens beyond 6 months,” says Dr. Maxime Taquet, the lead author of the research paper.

“The study cannot reveal the mechanisms involved but does point to the need for urgent research to identify these, with a view to preventing or treating them,” he adds.

Dr. Musa Sami, a clinical associate professor of psychiatry at the University of Nottingham, in the U.K., who was not involved in the research, agrees that the causes of the increased risk of neurological and mental health conditions were unclear.

He told the Science Media Centre, in London:

“What we do not fully understand at the moment is the mechanism by which COVID-19 has this effect — psychological stress, longer stays in hospital, and characteristics of the illness itself may play a part.”

Underestimated risks?

The authors of the present research acknowledge that studies like theirs, which are based on electronic health records, have some inherent weaknesses.

For example, the records may be incomplete, the diagnoses were not validated, and there was insufficient information about participants’ lifestyles and socioeconomic statuses.

In addition, the authors note that the flu and other respiratory tract infections are seasonal, so most occurred earlier in 2020 than the COVID-19 infections.

This may have led to an underestimation of the additional risks, as the majority of COVID-19 infections occurred when access to regular health services was limited by the pandemic.

In addition, some people in the control groups may have had undiagnosed COVID-19, which would also lead to an underestimation of the additional risks.

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