Covid-19 increases risk of some neurological and psychiatric conditions for two years following infection

Covid patients are at increased risk of developing some neurological and psychiatric conditions for two years following infection, compared to other respiratory infections.

Previous research has suggested that Covid-19 patients may be at increased risk of psychosis, dementia, ‘brain fog’, seizures, depression and anxiety for up to six months following infection, but there has been no large-scale study to examine the risks of these conditions over a longer time period.

To fill this gap, a team of researchers analysed data from over 1.25 million patient health records, mainly from the US, over a two-year period.

Risk of anxiety and depression two years following Covid infection same as other respiratory diseases

The study, published in The Lancet Psychiatry, included 1,284,437 people with a confirmed SARS-CoV-2 infection on or after January 20, 2020. These individuals were matched to an equal number of patients with another respiratory infection to act as a control group.

While the risk of having depression or anxiety increased in the immediate period following Covid-19 infection, it dropped to the same level as other respiratory infections after a relatively short time (depression at 43 days, anxiety at 58 days). After two years, there was no difference in the overall incidence of depression and anxiety between the Covid-19 group and the other respiratory infections group.

However, adults aged 18-64 who had Covid-19 up to two years previously had a higher risk of cognitive deficit, or ‘brain fog’, and muscle disease, compared to those who had other respiratory infections up to two years previously (Table 1).

Table 1. Adults aged 18-64, two years following infection

In adults aged 65 and over who had Covid-19 up to two years previously, there was a higher occurrence of ‘brain fog’, dementia and psychotic disorder compared to those who previously had a different respiratory infection (Table 2).

Table 2. Adults aged 65 and over, two years following infection

Children were at no greater risk of anxiety or depression following Covid-19 compared to any other infection. However, children with Covid were at greater risk of seizures and psychotic disorders in the two years following infection compared to other respiratory conditions (Table 3).

Table 3. Children (under 18), two years following infection

The researchers also looked at the differences between each variant of Covid-19. Overall, the delta and Omicron variant were associated with more disorders than the previous alpha variant.

Indeed, the emergence of the delta variant was associated with significantly higher six-month risks of anxiety (10% increased risk), insomnia (19% increased risk), cognitive deficit (38% increased risk), epilepsy or seizures (26% increased risk), and ischaemic strokes (27% increased risk).

However, there was a 40% decreased risk of dementia in those diagnosed with Covid-19 just before the delta wave compared to the previous alpha variant.

The risks during the omicron wave were similar to those when delta was the dominant variant.

Risk of developing neurological or psychiatric condition following Covid infection ‘still low’

Dr Max Taquet from the University of Oxford, who led the analyses, said while the findings are concerning, it is important to note that the risk of developing one of these conditions is still low.

He explains: “Our findings shed new light on the longer-term mental and brain health consequences for people following Covid-19 infection. 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. 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.”

More support for healthcare practitioners to diagnose and treat these neurological and mental health conditions

The researchers highlight some important limitations to the study. Firstly, the study may underrepresent self-diagnosed and asymptomatic cases of Covid-19 as these are unlikely to be recorded in electronic health records.

Secondly, they did not look at the severity or length of each condition after diagnosis or whether these are similar after Covid-19 than after other respiratory infections.

Despite this, they warn that the number of new Covid-19 cases is likely to lead to a relatively short-lived increase in the number of mood and anxiety conditions. For this reason, they are calling for more resources and support for mental health practitioners to diagnose and manage these conditions.

Additionally, the sustained increased risk for some neurological and psychiatric diagnoses over two years post-Covid-19 indicates that patients and clinicians must remain alert to the possibility of these delayed conditions.

Healthcare centres should be well supported to diagnose and treat these neurological and mental health conditions since new cases are likely to occur for a considerable time after the pandemic has subsided, the authors suggest.