Many Covid-19 survivors are likely to be at greater risk of developing mental illness, psychiatrists have said, after a large study found 20 per cent of those infected with the coronavirus are diagnosed with a psychiatric disorder within 90 days.

Anxiety, depression and insomnia were most common among recovered Covid-19 patients in the study who developed mental health problems, and the researchers also found significantly higher risks of dementia, a brain impairment condition.

“People have been worried that Covid-19 survivors will be at greater risk of mental health problems, and our findings ... show this to be likely,” said Paul Harrison, a professor of psychiatry at Britain’s Oxford University.