A study of 1.25 million patient records found that people with Covid-19 continued to be at risk of some neurological and psychiatric conditions up to two years after the infection.

The study also found that the Delta variant was associated with more disorders than the Alpha. Omicron too showed neurological and psychiatric risks, similar to those linked to Delta.

“Increased risk of some neurological and psychiatric conditions (such as dementia, psychosis and seizures) are still higher two years after the Covid-19 compared to other respiratory infections,” said the observational study published in The Lancet Psychiatry journal. But an increased risk of depression and anxiety in adults lasted less than two months before returning to rates comparable to those after other respiratory infections, the study added.

This was the first large-scale study to look at the risk of neurological and mental health conditions after Covid-19 in children, the study said, besides assessing the risk across new variants.

“The results have important implications for patients and health services as it suggests new cases of neurological conditions linked to Covid-19 infection are likely to occur for a considerable time after the pandemic has subsided. Our work highlights the need for more research to understand why this happens after Covid-19, and what can be done to prevent or treat these conditions,” said Professor Paul Harrison, lead author of the study, from the University of Oxford, United Kingdom.

Study details

The study analysed data on 14 neurological and psychiatric diagnoses gathered from the electronic health records, mostly from the United States over a two-year period. An equal number of patients with another respiratory infection acted as a control group, against which they were compared, the study explained,

Records from Covid-19 patients infected during different pandemic waves were also compared to investigate differences in the impact of the Alpha, Delta, and Omicron variants on the risk of neurological and psychiatric diagnoses.

Detailing the long-term effects, the study said, adults aged 18-64 who had Covid-19 up to two years previously had a higher risk of cognitive deficit, or ‘brain fog’, and muscle disease, compared to those who had other respiratory infections up to two years previously.

In adults aged 65 and over who had Covid-19 up to two years previously, there was a higher occurrence of ‘brain fog’, dementia and psychotic disorder, compared to those who previously had a different respiratory infection, the study noted.

“The likelihood of most neurological and psychiatric diagnoses after Covid-19 was lower in children than in adults, and they were not at greater risk of anxiety or depression than children who had other respiratory infections,”the study said. However, like adults, children were more likely to be diagnosed with some conditions, including seizures in the Covid-19 group.

Little change was observed in the risks of neurological and psychiatric diagnoses six months post Covid-19 just before and after the emergence of the alpha variant. “However, the emergence of the delta variant was associated with significantly higher six-month risks of anxiety, insomnia, cognitive deficit, epilepsy or seizures, and ischaemic strokes, but a lower risk of dementia when compared to those diagnosed with Covid-19 just before the delta wave. The risks during the omicron wave were similar to those when delta was the dominant variant,”the study found.

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