TORONTO -- COVID-19 has invaded all aspects of our waking lives -- and according to a new study on dreams, it’s also inside our sleeping minds.

Published last week in the journal Frontiers of Psychology, this new research out of Finland used computer modelling to track similarities across hundreds of peoples’ pandemic-related dreams.

"We were thrilled to observe repeating dream content associations across individuals that reflected the apocalyptic ambience of COVID-19 lockdown," said lead author Dr. Anu-Katriina Pesonen, head of the Sleep & Mind Research Group at the University of Helsinki, in a press release.

"The results allowed us to speculate that dreaming in extreme circumstances reveal shared visual imagery and memory traces, and in this way, dreams can indicate some form of shared mindscape across individuals."

More than 4,000 participants reported on the quality of their sleep over the sixth week of COVID-19 lockdown in Finland, with 811 people additionally reporting on the content of their dreams in that time.

A quarter of the participants reported having nightmares, and more than half of the dreams that were assessed to be nightmares or bad dreams were directly related to the pandemic.

In order to look for similarities in the hundreds of dream descriptions written out by participants, researchers plucked out keywords from each description that summed up the dream. These words, translated from Finnish to English, were then sorted by a computer into 33 dream clusters that aggregated dreams with similar motifs.

“For example, word pairs in a dream cluster labelled "disregard of distancing" included mistake-hug, hug-handshake, handshake-restriction, handshake-distancing, distancing-disregard, distancing-crowd, crowd-restriction and crowd-party,” the release explained.

The most common type of dream for all respondents who described them was having travel difficulties, with overcrowding somehow involved.

The second most common nightmare was the “disregard of distancing” cluster, in which other people — or the dreamer themselves — either purposefully or accidentally disregarded physical distancing. Surgery and medical complications due to COVID-19 came in third.

Some of the other common COVID-19-related nightmares involved dealing with quarantine, concerns about personal protective equipment, elderly people in trouble due to COVID-19, an event being cancelled, or the dreamer having COVID-19 symptoms.

Even some of the dream clusters that weren’t classified as nightmares were affected by COVID-19, such as people dreaming about the concept of touch, or about homeschooling.

More than half of the respondents indicated an increase in stress due to the pandemic, and the study noted that woman were more likely to be stressed and have more frequent nightmares.

Looking at the frequency of certain words in dream descriptions versus the level of stress participants had reported revealed different preoccupations as well.

The top five words to crop up in dreams of the most stressed participants were: coronavirus, death, work, friend and crowd.

The top five dream words for those who said their stress was unchanged were: crowd, friend, coronavirus, work and escape. Death was seventh on their list.

Sleep patterns outside of dreaming were also affected by the pandemic. Participants reported that they were sleeping twice as long, but many were more likely to wake up at some point during the night.

Researchers acknowledged that because participants were found through crowdsourcing, the study could have attracted more people who were experiencing issues with their sleep and wanted to vent.

But previous research has shown that large societal struggles such as war, natural disasters or outbreaks of disease do cause an increase in nightmares due to overall stress and increasing fear.

Pesonen said in the press release that researchers were excited not only by the implications of “shared imagery” in the dreams, but also by the results of a computational approach to dream research.

“We hope to see more AI-assisted dream research in future. We hope that our study opened the development towards that direction,” she said.