The global coronavirus pandemic affected just about everyone across the globe in ways that we're still trying to understand. It appears that one of the effects is that many of us became moodier along the way, often to the point of becoming more neurotic and less agreeable.

According to a new study of 7,109 people aged between 18 and 90, the shift was most noticeable in younger adults. Amongst the elderly people included in the research, there were no statistically significant changes.

Whereas previous research has suggested that collectively stressful but localized events – such as a natural disaster – don't move the needle on most personality traits, this study shows that global environmental pressures can indeed make a difference.

"There was limited personality change early in the pandemic but striking changes starting in 2021," say the authors of the study. "Of most note, the personality of young adults changed the most, with marked increases in neuroticism and declines in agreeableness and conscientiousness."

"That is, younger adults became moodier and more prone to stress, less cooperative and trusting, and less restrained and responsible."

The researchers used the Big Five personality trait model – covering neuroticism, extroversion, openness, agreeableness, and conscientiousness – to assess the study participants, with extroversion one of the traits taking a dip overall.

Considering the lockdowns that swept the world, limiting how often we could go out and interact with other people face-to-face, it's perhaps no surprise that we ended up less extroverted – a trait linked to being outgoing and getting joy from socializing with others.

Openness is another characteristic that now seems to be less prevalent after the pandemic.

The researchers report that taken as a whole, the personality shifts would normally take several years to occur.

"The changes were about one-tenth of a standard deviation, which is equivalent to about one decade of normative personality change," write the researchers in their published paper.

Interestingly, the declines in extroversion, openness, agreeableness, and conscientiousness happened during 2021 and 2022 but weren't significant in 2020. That suggests the stresses became different as the pandemic progressed, or that we had a delayed reaction to them.

As well as age groups, there were more pronounced differences in Hispanic and Latino populations, in terms of both the timings of the shifts in personality (they occurred earlier) and the level of the drops in extraversion, openness, and conscientiousness.

As the researchers note, this indicates that the stresses of the pandemic were not shared out equally – and that some parts of the community had it better than others in regards to the financial cost of COVID and how easily its risks could be avoided.

The next question is how permanent these changes are likely to be: whether they're going to last for years to come, or whether our personalities can bounce back to something like their previous state. That has important knock-on effects for our mental and physical health.

"We do not know yet whether these changes are temporary or will be lasting, but if they do persist, they could have long-term implications," says behavioral scientist Angelina Sutin from Florida State University.

"Neuroticism and conscientiousness predict mental and physical health, as well as relationships and educational and occupational outcomes, and the changes observed in these traits could increase risk of worse outcomes."

The research has been published in PLOS One.