(WTVO) — Patients with lingering COVID-19 symptoms can have them for more than a year.

That is the finding of a new Northwestern study. Researchers looked at 52 patients, each who got sick from COVID-19 without needing hospitalization. A vast majority are reportedly still suffering lingering effects up to 15 months later.

Brain fog and fatigue are the chief complaints.

“The fatigue becomes absolutely crushing. The cognitive symptoms, the brain fog,” said Emily Caffee, a participant in the study. “I did eventually return to work after a week being out sick, but if 100% was kind of my level beforehand, I returned to work as a barely functional adult.”

The study’s results are published in the “Annals of Clinical and Translational Neurology.”