Delirium and confusion may be common among some seriously-ill hospital patients with Covid-19, a study in The Lancet suggests.
Long stays in intensive care and being ventilated are thought to increase the risk, the researchers say.
Doctors should look out for depression, anxiety and post-traumatic stress disorder (PTSD) after recovery.
Most patients, particularly those with mild symptoms, will not be affected by mental health problems.
The evidence is based on studies of patients with severe acute respiratory syndrome (Sars) and Middle-East respiratory syndrome (Mers), as well early data on Covid-19 patients.