(CNN) As many people face the prospect of being alone for the holidays, new science is showing how loneliness might actually help build structures in the brain tied to imagination.
Lonely people were more likely to have increased activity in areas of the brain tied to reminiscing, thinking about others and future planning, according to a study published Tuesday in the journal Nature Communications.
The researchers had hypothesized that the so-called default network in the brain, which is involved in memory and social cognition, was likely to undergo changes related to loneliness.
"What surprised us was that overwhelmingly was the largest effect in the data," said lead study author Nathan Spreng, associate professor of neurology at McGill University in Montreal.
Ties between these areas had become strengthened and gray matter volume there was greater than in those who weren't lonely.
The results converged on the default network as most impacted by perceived isolation and loneliness.
Well before the pandemic, loneliness was increasingly being seen as a public health concern, enough so that the United Kingdom appointed a minister for loneliness in 2018.
Data has shown that lonely adults are about 1.64 times more likely to develop dementia compared with those who don't self-report loneliness, according to a 2015 review of worldwide studies.
Results like those motivated the researchers to comb through brain images from 40,000 subjects, all pulled from the UK Biobank, a large-scale database storing biomedical information from some 500,000 British people.
Participants in that study, who ranged in age from 40 to 69, filled out assessments that included questions asking whether they felt lonely or not.
The researchers then compared MRI scans of self-identified lonely people with those who did not feel loneliness on a regular basis.
The sheer size of the data sample is a rarity in this area of science, Spreng said, and it was the result of the biobank dramatically scaling up its available brain images this past February.
"We started working with that immediately when they came out and it was very exciting," Spreng said.
Prior to this, most of his neuroscience work had focused on cohorts with just hundreds of participants -- a significant number in itself. But now, with tens of thousands of subjects' data to draw from, there was a lot more to learn.
The researchers' hypothesis that the default network in the brain was active during loneliness was a logical one, because those are parts involved in thinking about self, according to Dr. Kenneth Heilman, professor emeritus in the University of Florida's department of neurology, whose books include "Creativity and the Brain" and "The Believer's Brain." Heilman, a fellow of the American Academy of Neurology, was not involved in the McGill study.
"There's an old, old saying in neurology that we always use. And that's 'use it or lose it,'" Heilman said.
Although parts of the brain primed for creativity and thinking about the self can grow during loneliness, that could mean that other social parts of the brain would atrophy from inactivity.
"The big question comes up, do you start losing other parts of the brain that are important for interactions?" Heilman asked. "If you don't use them, eventually, will that lead to more of a dementing kind of disorder?"
One key way this study could benefit medicine more broadly is by helping scientists better understand how social isolation -- an even more crucial topic during an isolating pandemic -- might change the structure of the brain, putting people at risk for Alzheimer's as they age.
"There's still a lot of other factors that need to be examined, like how does loneliness interact with APOE-4 genotype," Spreng said.
That gene has been linked to up to 25% of Alzheimer's cases, according to the Alzheimer's Association.
And because seniors at risk for dementia are often more isolated when living alone or in shared living facilities, more research could reveal how loneliness could exacerbate an already present genetic predisposition.
"This first study was really important in terms of identifying what parts of the brain are impacted by loneliness," he said. "We're using that information and we're following a large sample of older adults. We're seeing how their brain ages over multiple years, and how their experience of loneliness might actually accelerate atrophy patterns."
And the study has greater significance after a pandemic year in which social isolation is more common.
"Feeling socially connected is extremely important," Spreng said. "Coming out of Covid-related isolation will probably be a lot easier for some people, young adults in particular. Older adults may require more assistance."