People diagnosed with Covid-19 in the preceding six months were more likely to develop depression, dementia, psychosis and stroke, researchers have found.
A third of those with a Covid infection went on to develop or have a relapse of a previous psychological or neurological condition, the BBC reports.
Those admitted to hospital or in intensive care had an even higher risk. This is likely to be down to both the effects of the stress of hospitalisation, and the virus having a direct impact on the brain.
UK scientists looked at the electronic medical records of more than half a million patients in the US, to analyse their chances of developing one of 14 common psychological or neurological conditions, including: brain haemorrhage, stroke, Parkinson’s, and dementia.
Of the conditions searched for, anxiety and mood disorders were found to be the most common, and these were likely to be explained by the stress of the experience of being very ill or taken to hospital, researchers explained.
On the other hand, conditions like stroke and dementia were more likely to be down to the biological impacts of the virus itself, or of the body’s reaction to infection in general.
The study found that Covid-19 was not associated with an increased risk of Parkinson’s or Guillain-Barre syndrome, which is a risk from contracting flu.
The study was observational, so the researchers couldn’t say whether Covid had caused any of the diagnoses, and some people could have had a stroke or depression in the next six months regardless.
But by comparing a group of people who had had Covid-19 with two groups – with flu and with other respiratory infections respectively – the researchers at the University of Oxford concluded Covid was associated with more subsequent brain conditions than other respiratory illnesses.
The participants were matched by age, sex, ethnicity, and health conditions, to make them as comparable as possible.
Sufferers were 16% more likely to develop a psychological or neurological disorder after Covid than after other respiratory infections, and 44% more likely than people recovering from flu.
On top of this, the more severely ill with Covid the patient had been, the more likely they were to receive a subsequent mental health or brain disorder diagnosis
Dr Sara Imarisio, head of research at Alzheimer’s Research UK, said: “Previous studies have highlighted that people with dementia are at higher risk of developing severe Covid-19. This new study investigates whether this relationship may also hold in the other direction.
“The study doesn’t focus on the cause of this relationship and it is important that researchers get to the bottom of what underlies these findings.”
There is evidence the virus may enter the brain and cause direct damage, University of Oxford neurology professor Masud Husain said.
It can also have other indirect effects, for example by affecting blood clotting which can lead to strokes. Also, the general inflammation which happens in the body as it responds to infection can affect the brain, he said.
Professor Til Wykes, at the Institute of Psychiatry, Psychology and Neuroscience, King’s College London, said: “The study confirms our suspicions that a Covid-19 diagnosis is not just related to respiratory symptoms, it is also related to psychiatric and neurological problems.
“Looking over six months after diagnosis has demonstrated that the after effects can appear much later than expected – something that is no surprise to those suffering from Long Covid.”