MRI scans have shown some interesting ways in which loneliness appears to alter the human brain – specifically a part of the brain known as the default network, which is involved in inner thoughts such as reminiscing, future planning, imagination, and thinking about others.
Researchers found the default networks of lonely people were more strongly wired together and that grey matter volume in these regions was greater.
This may be because those who are lonely are more likely to use imagination, memories of the past or hopes for the future to overcome their social isolation.
Generally, greater grey matter volume in the brain signals a greater integrity of the neural circuit, explains Nathan Spreng, the study’s lead author, from The Neuro (the Montreal Neurological Institute-Hospital of McGill University). When people learn how to juggle, for example, the grey matter regions of motor cortex – the part of your brain involved in movement and control – increase in size.
Similarly, this new study found the regions of the default network may also grow in size with loneliness.
The default network is known to be involved in social information processing and memory. “Lonely people tend to imagine the social world to a greater degree, as well as imagine and reminisce about social experiences more,” says Spreng. “So, we think that in the absence of social stimulation in the world, the brain is compensating by upregulating these functions of the default network.”
Spreng says this “upregulation” leads to greater grey matter volume and a higher integrity of the fornix, which is the bundle of nerve fibres that carries signals from the hippocampus to the default network.
The study found loneliness correlated with differences in the fornix – in lonely people, the structure of this fibre tract was better preserved. “We do not have direct causal evidence of these changes, but this study does provide suggestive evidence to this effect,” he adds.
The findings were unearthed when Spreng and his co-worker Danilo Bzdok from McGill University in Canada examined MRI scans, genetics and psychological self-assessments of roughly 40,000 middle-aged and older adults from the UK Biobank – an open-access database available to scientists around the world.
They then compared the MRI data of participants who reported often feeling lonely with those who did not.
Loneliness is increasingly recognised as a major health problem. Past studies have found correlations between increased loneliness and a decrease in memory and poorer cognitive function overall. It’s also been linked to a greater risk of dementia, specifically Alzheimer’s disease.
Researchers said understanding how loneliness manifests in the brain could be key to preventing neurological disease and developing better treatments.
Bzdok, a researcher at The Neuro and the Quebec Artificial Intelligence Institute, says: “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.”
The study suggests the changes to the default network and fornix have to do with how social humans are and the importance of being immersed in a connected social environment. “In the absence of this experience of social connection, the brain appears to compensate,” adds Spreng.