It’s more than four years since the first cases of covid-19 were identified — but many of its longer-term effects, including for those living with long covid, remain unclear.

Now, a new study has some worrying findings that suggest covid may have longer-term effects on cognition and memory — and that these lead to measurable differences in cognitive performance.

The study, published Thursday in the New England Journal of Medicine, found that participants who recovered from covid symptoms had a cognitive deficit equivalent to three IQ points compared with those who were never infected, while participants suffering from unresolved covid symptoms lasting 12 weeks or more experienced a loss equivalent to six IQ points.