A study published Monday with the Lancet medical journal found that people who were bedridden for 7 days or more with COVID-19 were more likely to experience anxiety and depression a year after their diagnosis.

“Our findings are in line with the limited existing literature on both inpatients and outpatients, indicating a link between COVID-19 diagnosis and mental health status,” the study reported.

The study also found that milder COVID symptoms did not produce the same mental health stressors, and in fact may have improved mental health.

Unnnur Anna Vladimarsdottir, a psychiatric epidemiologist at the University of Iceland, who helped lead the research for this study, told USA Today that close to 80% of those who have had COVID-19 are not at high risk for mental health symptoms in the long term.

“The good news is that the patient group as a whole is not at higher risk of developing long-term (mental health) symptoms,” said Vladimarsdottir. “There might be a relief associated with having gone through the infection.”

“Individuals with a mild COVID-19 infection were able to return to somewhat more normal lives after the benign infection as compared with their more severely impacted counterparts who still could be restrained by fear of ongoing symptoms,” the study read.

However, the study could not confirm why those who ‌report more acute COVID symptoms, like those who were bedridden for a week or more, are more at risk for long-term negative mental health symptoms like anxiety and depression.

Also, since the study began before the pandemic, long COVID was still not a concept people were widely familiar with. So, experiencing lingering symptoms and having no explanation for them may have contributed to some of the depression and anxiety experienced in those with more severe cases of COVID.

The anxiety and depression seen in acute cases of COVID could also result from the virus itself and its effects on the brain. More research is necessary to understand the long-term effects of COVID.

“In conclusion, in this study, we found that severe COVID-19 acute illness was associated with long-term mental health symptomology among recovered patients,” the study revealed.

“More than a fifth of the included patients with COVID-19 had a severe acute illness course (the large majority at home, although some in hospital), which was associated with persistent risks of depressive and anxiety symptoms up to 16 months after diagnosis,” the study concluded.