COVID-19 has infiltrated our dreams and nightmares, according to researchers at the University of Helsinki. People are traveling back to their high school or college days in recurring dreams and experiencing attacks of anxiety that relate to a lack of social distancing and contracting the disease.

According to Ladders, the Finnish researchers used artificial intelligence to decode the distressing dreams in which participants forgot to attend a class or finish an assignment. Half the dreams included references to the pandemic.

“We were thrilled to observe repeating dream content associations across individuals that reflected the apocalyptic ambiance of COVID-19 lockdown,” said professor Anu-Katriina Pesonen, who was the lead study author. “The findings enabled us to speculate that dreaming in the middle of exceptional circumstances is a form of shared mindscape between individuals,” she added in a news release.

Many of the themes the researchers observed in the dreams of 4,000 study participants had COVID-19 content. For example, people dreamed about shaking hands or attending large parties, ignoring social distancing measures, and had nightmares about subsequently falling ill.

According to the news release, participants said they were sleeping more than ever, but 10% said they had trouble falling asleep, and 25% reported having more nightmares than before the pandemic. More than half admitted that their stress levels increased, and those who experienced the most severe stress also had more COVID-19 associated dreams, according to the study.

A similar study conducted by Harvard Medical School showed that pandemic nightmares have become widespread. One common theme, said Harvard psychology professor Deirdre Barrett, are dream clusters about being attacked by bugs, a dream that is unique to the coronavirus.

“I had never seen one of those after 9/11 or after World War II,” Barrett said, according to Live Science.