While severe COVID-19 is associated with a significantly higher risk for psychiatric and neurologic disorders a year after infection, mild does not carry the same risk, a new study shows.
However, less severe COVID-19 was not linked to a higher incidence of psychiatric diagnoses and was associated with only a slightly higher risk for neurologic disorders.
The new research challenges previous findings of long-term risk for psychiatric and neurologic disorders associated with SARS-CoV-2 in patients who had not been hospitalized for the condition.
“Our study does not support previous findings of substantial post-acute neurologic and psychiatric morbidities among the general population of SARS-CoV-2-infected individuals but does corroborate an elevated risk among the most severe cases with COVID-19,” the authors wrote.
The study was published online on February 21 in Neurology.
‘Alarming’ Findings
Previous studies have reported nervous system symptoms in patients who have experienced COVID-19, which may persist for several weeks or months after the acute phase, even in milder cases.
But these findings haven’t been consistent across all studies, and few studies have addressed the potential effect of different viral variants and vaccination status on post-acute psychiatric and neurologic morbidities.
“Our study was partly motivated by our strong research interest in the associations between infectious disease and later chronic disease and partly by international studies, such as those conducted in the US Veterans Health databases, that have suggested substantial risks of psychiatric and neurological conditions associated with infection,” senior author Anders Hviid, MSc, DrMedSci, head of the department and professor of pharmacoepidemiology, Statens Serum Institut, Copenhagen, Denmark, told this news organization.
Investigators drew on data from the Danish National Patient Registry to compare the risk for neurologic and psychiatric disorders during the 12 months after acute COVID-19 infection to risk among people who never tested positive.
They examined data on all recorded hospital contacts between January 2005 and January 2023 for a discharge diagnosis of at least one of 11 psychiatric illnesses or at least one of 30 neurologic disorders.
The researchers compared the incidence of each disorder within 1-12 months after infection with those of COVID-naive individuals and stratified analyses according to time since infection, vaccination status, variant period, age, sex, and infection severity.
The final study cohort included 1.8 million individuals who tested positive during the study period and 1.5 who didn’t. Three quarters of those who tested positive were infected primarily with the Omicron variant.
Hospitalized vs Nonhospitalized
Overall, individuals who tested positive had a 24% lower risk for psychiatric disorders during the post-acute period (incident rate ratio [IRR], 0.76; 95% CI, 0.74-0.78) compared with the control group, but a 5% higher risk for any neurologic disorder (IRR, 1.05; 95% CI, 1.04-1.07).
Age, sex, and variant had less influence on risk than infection severity, where the differences between hospitalized and nonhospitalized patients were significant.
Compared with COVID-negative individuals, the risk for any psychiatric disorder was double for hospitalized patients (IRR, 2.05; 95% CI, 1.78-2.37) but was 25% lower among nonhospitalized patients (IRR, 0.75; 95% CI, 0.73-0.77).
For neurologic disorders, the IRR for hospitalized patients was 2.44 (95% CI, 2.29-2.60) compared with COVID-negative individuals vs an IRR of only 1.02 (95% CI, 1.01-1.04) among nonhospitalized patients.
“In a general population, there was little support for clinically relevant post-acute risk increases of psychiatric and neurologic disorders associated with SARS-CoV-2 infection without hospitalization. This was particularly true for vaccinated individuals and for the more recent variants,” the authors wrote, adding that the only exception was for change in sense and smell.