What does loneliness do to the brain?

Loneliness can be defined as the distress a person experiences due to a discrepancy between perceived and desired social relationships. It is different from social isolation, or the number of social contacts someone has [1].

How loneliness affects the brain

The so called “loneliness epidemic” is a paradox of today’s society. Despite innovations like the internet and social media facilitating connections between people across the World, we are lonelier than ever with an estimated 3.83 million people in Great Britain experiencing chronic loneliness [2]. This has even led to the development of the first loneliness strategy for the UK in 2018. But is loneliness in any way reflected in our brains? And why is understanding this important to ensure good mental health?

Numerous studies have linked loneliness with the risk of mortality and morbidity, meaning that lonely people are more likely to become sick more often, and have shorter lives than people who do not feel lonely. Imaging studies have also found that lonelier individuals have different grey and white matter volumes in different areas and systems of the brain [1].  

Brain areas associated with loneliness  

Researchers have found that some areas of the brain, including the prefrontal cortex, insula, hippocampus, and amygdala, are different in lonely people. The prefrontal cortex is responsible for higher-order functioning, personality, and inhibition – in short, a lot of what makes us who we are. Some of these areas are also involved in the way people process real-world social interactions and social rejection, and the extent to which brief feelings of social distress are linked to how people perceive their own overall social disconnection.

A study has found that those with more activity in the affective and pain processing areas of the brain (e. g. dorsal anterior cingulate cortex, amygdala), during these interactions were more likely to feel social distress only briefly, whereas those showing more activity in regions associated with autobiographical memory (e. g. hippocampus, medial prefrontal cortex) showed a greater correspondence between the brief experiences of social distress and their end-of-day assessments, suggesting that brief experiences of social rejection may lead to general feelings of not being accepted by others or belonging to a community [3].   

The insula has been implicated in self-awareness and affect generation like pain, meaning it is an area of the brain strongly associated with creation of emotion. It therefore is not surprising that changes in white and grey matter connectivity in this area have also been associated with loneliness [4].  

As many readers may know, the hippocampus plays a significant role in memory. White matter structural efficiency and smaller grey matter volume were found to be strongly associated with loneliness, especially in older adults [5].  

The amygdala is critical to our threat-perception and fight or flight response. Numerous studies have demonstrated that the amount of grey-matter in this area of the brain is associated with loneliness, especially in males and older people [6]. 

Brain networks

Some studies have found that the primary visual cortex of lonely females is more reactive to unpleasant social stimuli than unpleasant non-social stimuli compared to non-lonely females and males. This means that lonely females are more likely to focus on negative social images and potential social threats [6].  

Loneliness can make ignoring irrelevant information more difficult too. This is because it is linked with poorer connectivity between dorsal (focus) and ventral (shift) attentional networks [7].   

Other studies have found that reduced connectivity in the default mode network (DMN), which supports self-referential processes like autobiographical memory and interoception, was associated with increased loneliness, higher social disability, and smaller social networks [8]. This effect was especially evident when researchers compared healthy older adults and adults with long-lasting depression. They found that those with long-lasting depression processed negative stimuli differently than healthy older adults, suggesting that areas of the brain that have been implicated in rumination – the replaying negative social interactions in the mind – and negative feelings, are also associated with loneliness. 

So, can loneliness change the structure of the brain? We would say the short answer is yes. Although we cannot pinpoint a single “loneliness centre”, and there is still much we do not yet know, researchers have certainly begun to sketch the structure of the lonely brain. It is hoped that understanding the biological bases of loneliness will lead to the development of therapeutic and preventive interventions that will reduce the negative impact of this epidemic [1].  

What to do when you feel lonely 

In the meantime, here are some agencies that people who have been struggling with loneliness can contact. You are not alone.    

• NHS 
• Campaign to end loneliness 
• Mind 
• Red Cross 
• Marmalade Trust 

References 

[1] Lam, J.A., Murray, E.R., Yu, K.E., Ramsey, M., Nguyen, T.T., Mishra, J., & Lee, E.E. (2021). Neurobiology of loneliness: a systematic review. Neuropsychopharmacology, 46(11), 1873-1887. https://doi.org/10.1038/s41386-021-01058-7 

[2] Campaign to end loneliness. (2024, February 23). Facts and statistics about loneliness. https://www.campaigntoendloneliness.org/facts-and-statistics/#:~:text=Approximately%207.1%25%20of%20people%20in,or%20always’%20%5B2%5D. 

[3] Eisenberger, N. I., Gable, S. L., & Lieberman, M. D. (2007). Functional magnetic resonance imaging responses relate to differences in real-world social experience. Emotion, 7(4), 745-754.

[4] Nakagawa S, Takeuchi H, Taki Y, Nouchi R, Sekiguchi A, Kotozaki Y, et al. (2015). White matter structures associated with loneliness in young adults. Scientific Reports, 5(1), 17001

[5] Düzel S, Drewelies J, Gerstorf D, Demuth I, Steinhagen-Thiessen E, Lindenberger U, et al. (2019). Structural brain correlates of loneliness among older adults. Scientific Reports, 9(1), 13569.

[6] Kiesow H, Dunbar R, Kable J, Kalenscher T, Vogeley K, Schilbach L, et al. (2020). 10,000 social brains: sex differentiation in human brain anatomy. Science Advances, 6(12), eaaz1170.

[7] Tian, Y., Yang, L., Chen, S., Guo, D., Ding, Z., Tam, K. Y., & Yao, D. (2017). Causal interactions in resting-state networks predict perceived loneliness. PloS One, 12(5), e0177443.

[8] Wong NM, Liu HL, Lin C, Huang CM, Wai YY, Lee SH, et al. (2016). Loneliness in late-life depression: structural and functional connectivity during affective processing. Psychological Medicine, 46(12), 2485-2499.