At least one-third or 34% of Covid-19 survivors were diagnosed with a neurological or psychiatric condition within six months after being infected, showed a study published in The Lancet Psychiatry journal on Wednesday. Almost 13% of these patients had never received a neurological or psychiatric diagnosis before.

Led by Oxford University researchers, the study, which analysed the health records of more than 2,30,000 patients in the United States, stated that the SARS-CoV-2 virus causes serious disorders that affect the nervous system. The data was compared with that of 1,05,579 patients diagnosed with influenza and 2,36,038 patients diagnosed with other respiratory tract infections.

The most common diagnoses after Covid-19 were anxiety disorders, found in 17% of the patients, mood disorders in 14%, substance misuse disorders (7%) and insomnia (5%). Neurological problems were fewer. About 0.6% patients suffered a brain haemorrhage, 2.1% recorded ischaemic stroke, and 0.7% suffered dementia.

“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 that many of these conditions are chronic,” Paul Harrison, lead author of the study, from the University of Oxford, said in a statement. “As a result, health care systems need to be resourced to deal with the anticipated need, both within primary and secondary care services.”

The study further identified distinctions within the severity of the infection. Of the patients who were diagnosed with neurological or psychiatric condition, 38% of them had been admitted to hospital for Covid-19, while 62% had delirium while infected.

“Our results indicate that brain diseases and psychiatric disorders are more common after Covid-19 than after flu or other respiratory infections, even when patients are matched for other risk factors,” said Dr Max Taquet, a co-author of the study, from the University of Oxford. “We now need to see what happens beyond six months. 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.”

There have been several other studies that have established a link between coronavirus and increased risk of neurological disorders. Previously, the same research group had concluded that Covid-19 survivors are at increased risk of mood and anxiety disorders in the first three months after infection. In October, another study found that about 4 out of 5 patients hospitalised with Covid-19 suffer neurological symptoms, including muscle pain, headaches, confusion, dizziness and the loss of smell or taste. Another study from Wuhan in China found that 36% of patients had neurological symptoms ranging from headaches to impaired consciousness.

As of Wednesday, the coronavirus has infected more than 13.23 crore people and killed 28,71,781 worldwide, according to the Johns Hopkins University. More than 7.51 crore people have recovered from the infection. India on Wednesday recorded 1,15,736 cases of coronavirus cases, the most infections reported in the world in a single day since the pandemic began, data from the health ministry showed.