Research to Better Understand Loneliness

Neurobiology of loneliness: a systematic review

Lam, J. A., Murray, E. R., Yu, K. E., Ramsey, M., Nguyen, T. T., Mishra, J., Martis, B., Thomas, M. L., & Lee, E. E. (2021). Neurobiology of loneliness: a systematic review. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 46(11), 1873–1887. https://doi.org/10.1038/s41386-021-01058-7

• “Loneliness is associated with increased morbidity and mortality. Deeper understanding of neurobiological mechanisms underlying loneliness is needed to identify potential intervention targets.”
• “We did not find any systematic review of neurobiology of loneliness. Using MEDLINE and PsycINFO online databases, we conducted a search for peer-reviewed publications examining loneliness and neurobiology. We identified 41 studies (n = 16,771 participants) that had employed various methods including computer tomography (CT), structural magnetic resonance imaging (MRI), functional MRI (fMRI), electroencephalography (EEG), diffusion tensor imaging (DTI), single-photon emission computed tomography (SPECT), positron emission tomography (PET), and post-mortem brain tissue RNA analysis or pathological analysis.”
• “Our synthesis of the published findings shows abnormal structure (gray matter volume or white matter integrity) and/or activity (response to pleasant versus stressful images in social versus nonsocial contexts) in the prefrontal cortex (especially medial and dorsolateral), insula (particularly anterior), amygdala, hippocampus, and posterior superior temporal cortex. The findings related to ventral striatum and cerebellum were mixed. fMRI studies reported links between loneliness and differential activation of attentional networks, visual networks, and default mode network. Loneliness was also related to biological markers associated with Alzheimer’s disease (e.g., amyloid and tau burden).”
• “Although the published investigations have limitations, this review suggests relationships of loneliness with altered structure and function in specific brain regions and networks. We found a notable overlap in the regions involved in loneliness and compassion, the two personality traits that are inversely correlated in previous studies.”

The default network of the human brain is associated with perceived social isolation

Spreng, R. N., Dimas, E., Mwilambwe-Tshilobo, L., Dagher, A., Foellinger, P., Nave, G., Ong, A., Kernbach, J. M., Wiecki, T. V., Ge, T., Li, Y., Holmes, A. J., Yeo, B., Turner, G. R., Dunbar, R., & Bzdok, D. (2020). The default network of the human brain is associated with perceived social isolation. Nature communications, 11(1), 6393. https://doi.org/10.1038/s41467-020-20039-w

• “Humans survive and thrive through social exchange. Yet, social dependency also comes at a cost. Perceived social isolation, or loneliness, affects physical and mental health, cognitive performance, overall life expectancy, and increases vulnerability to Alzheimer’s disease-related dementias.”
• “Despite severe consequences on behavior and health, the neural basis of loneliness remains elusive. Using the UK Biobank population imaging-genetics cohort (n = ~40,000, aged 40–69 years when recruited, mean age = 54.9), we test for signatures of loneliness in grey matter morphology, intrinsic functional coupling, and fiber tract microstructure.”
• “The loneliness-linked neurobiological profiles converge on a collection of brain regions known as the ‘default network’. This higher associative network shows more consistent loneliness associations in grey matter volume than other cortical brain networks. Lonely individuals display stronger functional communication in the default network, and greater microstructural integrity of its fornix pathway.”
• “The findings fit with the possibility that the up-regulation of these neural circuits supports mentalizing, reminiscence and imagination to fill the social void.”

Social isolation and loneliness: the new geriatric giants: Approach for primary care

Freedman, A., & Nicolle, J. (2020). Social isolation and loneliness: the new geriatric giants: Approach for primary care. Canadian family physician Medecin de famille canadien, 66(3), 176–182.

• “Objective: To review the problems of social isolation, loneliness, and social vulnerability in older adults and the associated risks, and to help primary care providers identify patients at risk and recommend effective interventions.”
• “Social isolation, loneliness, and social vulnerability are very common in older adults and are associated with considerable morbidity and mortality, comparable to established risk factors such as smoking, alcohol consumption, obesity, and frailty.”
• “Numerous interventions addressing loneliness and social isolation have been studied: social facilitation (including technology), exercise, psychological therapies, health and social services, animal therapy, befriending, and leisure and skill development. However, current evidence of effectiveness is limited.”
• “A patient-centred approach is essential to the selection of interventions. The needs of underserviced and marginalized populations, including new immigrants, older adults identifying as LGBTQ+ (lesbian, gay, bisexual, transgender, queer or questioning, and related communities), Indigenous seniors, and seniors living in poverty, as well as the needs of long-term care residents and older caregivers, require further evaluation.”
• “Conclusion: Social isolation, loneliness, and social vulnerability are common problems in older adults and have important health consequences. Family physicians are uniquely positioned to identify lonely and socially isolated older adults and to initiate services.”

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