The diagnosis estimate was much higher for patients admitted to intensive care units (ITU), with the percentage rising to 46.42 percent. The study analyzed the outcome in 236,379 mostly US patients diagnosed with COVID-19.

Researchers examined the incidences of 14 neurological and psychiatric outcomes, including dementia, anxiety disorders, insomnia and Parkinson's disease. High percentages of anxiety disorder (19.15 percent) and psychotic disorder (2.77 percent) were recorded, however, doctors have said they are unsure as to why patients who were previously ill with COVID-19 experienced such after-effects.

"Most diagnostic categories were more common in patients who had COVID-19 than in those who had influenza ... and those who had other respiratory tract infections," the study explains.

The study also showed that, among patients admitted to ITU with severe COVID-19, seven percent experienced a stroke within six months of their admittance and two percent were diagnosed with dementia.

"The present data show that COVID-19 is followed by significant rates of neurological and psychiatric diagnoses over the subsequent 6 months. Services need to be configured, and resourced, to deal with this anticipated need," the study concluded.

There is currently no scientific explanation to define a link between neurological and psychiatric outcomes and COVID-19. Past studies by the same researchers showed that 20 percent of former COVID-19 patients were diagnosed with some form of mental illness within three months of their COVID-19 diagnosis.