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Published: 10 April 2025

Blood Proteins Reveal Biological Effects of Social Isolation

A recent study, published in the online journal Nature Human Behaviour, demonstrates how the health effects of isolation and loneliness in humans can be studied through the analysis of human blood proteins. Unlike the traditional animal studies, this approach offers valuable insights that are directly relevant to human health.

Researchers from Fudan University in Shanghai, China, and the University of Cambridge, UK, examined the blood protein profile – known as the plasma proteome. The study was based on data from over 42,000 participants in the UK Biobank, providing new insights into the biological mechanisms associated with loneliness.

By analyzing more than 2,900 blood proteins, the study identified five proteins that are elevated in people experiencing loneliness. These proteins play a central role in inflammation and immune response (1). Alarmingly, more than half of these proteins are associated with an increased risk of cardiovascular diseases, diabetes, stroke, and a shortened life expectancy (1).

Until now, loneliness has mainly been considered a psychological burden. However, the new findings emphasize that social isolation has profound biological consequences Chronic loneliness can intensify inflammatory processes and weaken the immune system, increasing the risk of serious health issues (1). The study underscores the importance of recognizing loneliness as a serious health risk and developing targeted prevention and intervention measures.

Loneliness and social isolation have often been studied in animal experiments, such as those where rats or mice were kept in isolation. For example, in one study, mice were isolated for 30 weeks, leading to behavioral changes like hesitation to enter open areas in a maze and increased daytime activity in nocturnal animals.This behavior was interpreted as an anxiety-driven response (2).

According to Doctors Against Animal Experiments (DAAE), such experiments are unsuitable for studying complex social phenomena like human loneliness. The complex emotional and cognitive experiences of humans cannot be adequately reflected in animal models. Additionally, the human immune system, which was found to be strongly affected by loneliness in the current study, differs significantly from that of animals. These differences further emphasize the importance of using human data to understand the biological effects of loneliness. In the opinion of DAAE, only human-relevant research can provide precise and reliable results, leading to effective health promotion strategies.

References

(1) Shen C et al. Plasma proteomic signatures of social isolation and loneliness associated with morbidity and mortality. Nature Human Behaviour 2025; doi:10.1038/s41562-024-02078-1

(2) Benfato ID et al. Effects of long-term social isolation on central, behavioural and metabolic parameters in middle-aged mice. Behavioural Brain Research 2022; 417:113630