Loneliness isn’t just a feeling; it appears to deeply affect our brain networks. When nobody is around, our imagination might fill the void. Researchers led by Nathan Spreng from Canada’s McGill University have found that lonely brains have a distinct wiring of neural networks that form a “signature” of loneliness.
This signature is strongest in the brain regions linked to remembering and imagining – called the default network – and this suggests that loneliness makes us reminisce and imagine happy times or loved ones more, to ease the social void.
Loneliness is estimated to affect up to 20% of adults, and is closely related to hypertension, immune dysfunction and even early death. It is also a major risk in older people, as it can lead to cognitive decline and dementia for currently unknown reasons.
“We are just beginning to understand the impact of loneliness on the brain. Expanding our knowledge in this area will help us to better appreciate the urgency of reducing loneliness in today’s society,” says Danilo Bzdok, co-author of a paper in Nature Communications.
The team used machine learning to compare genetics and MRI scans of the brains of 40,00 middle-aged adults with self-assessed loneliness. They found that the self-proclaimed lonely brain activity centred around the brain regions that focused on future planning, imagining, reminiscing and thinking about other people.
The nerve fibres that carry signals to the hippocampus during this processing were better preserved in lonely people.
Potentially, this happens because lonely people must rely on memories and imagination instead of social interaction to fill their social needs, so the imagination part of the brain gets more of a workout.
“In the absence of desired social experiences, lonely individuals may be biased towards internally-directed thoughts such as reminiscing or imagining social experiences. We know these cognitive abilities are mediated by the default network brain regions,” says Spreng.
“So this heightened focus on self-reflection, and possibly imagined social experiences, would naturally engage the memory-based functions of the default network.”
Interestingly, there was also a small difference between men and women. They found that men had a more prominent association between brain structure and loneliness, so there may be slight variation between sexes.
However, they also note that this might be due to social stigma against men reporting loneliness and urge further research.
Deborah Devis is a science journalist at Cosmos. She has a Bachelor of Liberal Arts and Science (Honours) in biology and philosophy from the University of Sydney, and a PhD in plant molecular genetics from the University of Adelaide.
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