Why and how our dreams are affected by our daily lives has long fascinated scientists, and a new study sheds some light on how the spread of COVID-19 – and the ongoing changes in our habits – is impacting what we dream about.

Anger and sadness have become more common in dreams as the pandemic has progressed, the study found, and there are stronger links with themes like contamination and cleanliness as we deal with the spread of the virus.

While dreams are already thought to be a natural continuation of what's happening during the time we're awake, this new research gives scientists some interesting insights into how social distancing and hand washing might be more on our dream minds than actually catching COVID-19.

"These results corroborate the hypothesis that pandemic dreams reflect mental suffering, fear of contagion, and important changes in daily habits that directly impact socialisation," write the researchers in their paper, which has been published in PLOS One.

The team looked at a total of 239 dream reports submitted by 67 different people in Brazil, from both before and after lockdowns were imposed in March and April when the coronavirus pandemic began to take hold.

There was a statistically significant rise in the number of words related to anger and sadness in the pandemic dreams, and a rise in words related to contamination and cleanliness (the word "bathroom" would qualify, for example).

Pandemic dreams also presented more words in general, although there was no substantial difference in the number of words related to sickness, health, death or life. The number of words related to positive and negative emotions stayed about the same too.

The dream report comparison "reflects a collective traumatic experience, as is often the case during plagues, wars and natural disasters" write the researchers in their paper.

The focus on changing daily habits around lockdowns, rather than worries about sickness or death, may be because the dream reports were collected early on in the first wave of the pandemic, suggest the study authors (only one participant in the study reported being diagnosed with COVID-19).

It's no real surprise that our night-time dreams are changing as our daily lives are changing – scientists have long accepted that dreams are a way for our brains to process our experiences and emotions – but it's interesting to see these shifts in specific detail as we all experience similar disruptions in the way we're living.

The coronavirus pandemic has also seen a rise in the number of people having vivid dreams, something that experts say could be caused by disrupted sleep schedules – or just having a lot more to process and deal with at the end of every day.

"Overall, our results are consistent with the hypothesis that dreams during the lockdown period reflect the waking challenges presented by the COVID-19 pandemic," write the researchers in their paper.

The research has been published in PLOS One.