The risk of developing dementia, psychosis or brain fog remains higher for two years for patients who have had Covid-19 than it does for those with other respiratory diseases, a major study has found.
Neurological and psychiatric effects of Covid-19 also include a heightened risk of depression and anxiety for a short period after contracting the virus, although at two years there is no difference when compared with patients with other respiratory diseases.
“It is worrying that some other conditions, such as dementia, continue to be more frequently diagnosed after Covid-19″
Max Taquet
The observational study, of 1.25m people, which was published in The Lancet Psychiatry this week, also found that the delta variant of Covid-19 was associated with more psychiatric disorders than the previous alpha variant, and that the omicron variant had similar neurological and psychiatric risks to the delta variant.
There had been evidence since the pandemic began that those who had contracted Covid-19 may be at increased risk of neurological and psychiatric conditions. A previous observational study by the same team of researchers from Oxford University found a heightened risk at six months after infection.
Their latest study analysed data on 14 psychiatric and neurological diagnoses from patient records, mainly in the US, looking at infections from different waves of the pandemic, as well as studying data from a similar number of patients infected with other respiratory diseases over the same period.
The study found that although there was an increased risk of adults suffering depression after Covid-19, it lasted only 43 days, and for anxiety the figure was 58 days.
But the risk of being diagnosed with other neurological disorders lasted longer, with 640 cases of cognitive deficit per 10,000 patients aged 18-64 being recorded two years after Covid-19. This was compared with 550 cases per 10,000 patients for those who had had other respiratory infections.
In patients over 65, the number of dementia diagnoses was 450 per 10,000 for those who had had Covid-19, compared with 330 per 10,000 for those who had had other respiratory diseases.
In addition, also in adults aged over 65 who had Covid-19 up to two years previously, there was a higher occurrence of ‘brain fog’, with 1,540 cases per 10,000 people. This was compared to those who previously had a different respiratory infection which accounted for 1,230 cases per 10,000 for brain fog.
Overall, the likelihood of most neurological and psychiatric diagnoses after Covid-19 was lower in children than in adults, and they were not at greater risk of anxiety or depression than children who had other respiratory infections.
However, like adults, children were more likely to be diagnosed with some conditions, including seizures and psychotic disorders, over the two years following Covid-19, researchers found.
“The emergence of the delta variant was associated with an increase in risk for several conditions”
Max Taquet
For example, there were 260 cases of seizures per 10,000 in children within the Covid-19 group, compared with 130 cases per 10,000 in the group with other respiratory diseases.
“It is good news that the higher risk of depression and anxiety diagnoses after Covid-19 is relatively short-lived and there is no increase in the risk of these diagnoses in children,” said Dr Max Taquet from the University of Oxford, who led the analyses.
“However, it is worrying that some other conditions, such as dementia and seizures, continue to be more frequently diagnosed after Covid-19, even two years later.
“The emergence of the delta variant was associated with an increase in risk for several conditions; however, it’s important to note that the overall risk of these conditions is still low.
“With omicron as the dominant variant, although we see much milder symptoms directly after infection, similar rates of neurological and psychiatric diagnoses are observed as with delta, suggesting that the burden on the healthcare system may continue even with variants that are less severe in other respects.”
