Over a third of COVID-19 survivors experience a neurological or mental-health condition in the 6 months after infection, a large-scale study finds

• One in three people with COVID-19 had neurological or mental health conditions in the six months following illness in a new study.
• Anxiety and mood disorders were the most common following COVID-19.
• People with severe illness were at highest risk of rarer neurological complications, the study found.

One in three people infected with COVID-19 develop a neurological or mental-health condition in the six months after, a large study published in Lancet Psychiatry on Wednesday found.

Diagnoses for these conditions were on average 44% more common after COVID-19 than after flu, and the risk increased with the severity of illness, particularly for neurological disorders, the study authors from Oxford University said.

The study looked at more than 236,000 electronic health records, mostly belonging to Americans, and compared people who had COVID-19 with those who hadn't.

The researchers said that, while some neurological effects are more common in hospitalized patients, these symptoms were spotted even in patients with mild cases, suggesting more research is needed on the mental health and neurological impact of a COVID-19 infection.

Paul Harrison, a professor of psychiatry at Oxford University and lead author of the study, told Insider that he expected there to be overlap with long-COVID, whereby people experience COVID-19 symptoms including neurological features and mental health conditions for a number of months after the illness. But he said whether long COVID-19 was more common after severe illness, versus mild, was still unclear.

"We need urgent research to understand how and why the disorders occur and how they can be treated and prevented," Harrison and his fellow authors said in a press briefing.

Symptoms included anxiety and brain bleeds

The most common mental health conditions in the six months after catching COVID-19 were anxiety and mood disorders: 17% of people were diagnosed with anxiety, and 14% of people with a mood disorder, the study found.

The risk of both anxiety and mood disorder increased in patients who got unwell with an altered mental state known as encephalopathy, a sign of systemic infection to 22%. But generally the severity of COVID-19 illness didn't impact the likelihood of a mental health condition.

Neurological complications like stroke, brain bleeds, and dementia were less common. People with severe COVID-19 were at highest risk - 4% of those who were hospitalized and 7% of people that went to ITU were diagnosed with stroke six months after.

Paul Harrison, lead author of the study, said in a statement Tuesday that the results, "confirm the high rates of psychiatric diagnoses after COVID-19, and show that serious disorders affecting the nervous system (such as stroke and dementia) occur too."

Harrison added: "While the latter are much rarer, they are significant, especially in those who had severe COVID-19."

Read more: COVID-19 Vaccine Tracker: AstraZeneca's shot proves safe and effective, and is headed to the FDA

An expert says the report 'confirms our suspicions' that COVID-19 will have psychiatric repercussions

It is too early to make definitive statements or identify the specific mechanisms by which the coronavirus is affecting the neurological system.

The study authors said in a press briefing Tuesday that it was likely to be different mechanisms at play affecting the different disorders. Mental health conditions could be influenced by the effects of the pandemic too, they said.

It was also not clear whether people predisposed to certain conditions were at higher risk - the study found just 13% people overall were diagnosed with a neurological or mental health illness for the first time.

The authors used routine healthcare data which means there could be missing or incorrect diagnosis. It is also not known how bad the mental health or neurological conditions were and whether people recovered after the six month period.

Nonetheless, the study adds to a growing body of evidence that COVID-19 causes neurological and mental health effects, both at the time of illness as well as afterwards.

"The study confirms our suspicions that a COVID-19 diagnosis is not just related to respiratory symptoms, it is also related to psychiatric and neurological problems," Dame Til Wykes, professor of psychology and neuroscience at King's College London said in a statement.