A new study by researchers from the UK and China has revealed the profound impact of social connections on physical health. Analyzing blood proteins from over 42,000 adults, the research shows that interactions with friends and family significantly boost the immune system and protect against diseases. Conversely, prolonged loneliness increases vulnerability to conditions like heart disease, stroke, and type 2 diabetes.

Social isolation and loneliness are not merely psychological states; they’re important factors affecting physical health. Humans are inherently social creatures, and our connections play a key role in maintaining overall well-being. When these connections are lacking, the body activates stress responses that can compromise health.

Doctors and scientists are starting to realize just how big this impact can be.

Social isolation and loneliness are increasingly recognized as global health concerns. Their impact on health is comparable to risk factors like smoking and obesity.

In the new study, researchers showed just how much of an impact loneliness can have.

The researchers first calculated social isolation and loneliness scores. The two are not the same: social isolation is an objective measure that considers whether someone lives alone and how often they meet and interact with family and friends or attend social events. Meanwhile, loneliness is a subjective measure. Social isolation is how often you meet with others (or lack these interactions) and loneliness is how you feel.

The study identified over 175 proteins associated with social isolation and 26 linked to loneliness, with significant overlap between the two. When the researchers corrected for factors like age, sex, and socioeconomic background, they found that approximately 85% of the proteins associated with loneliness were shared with social isolation.

Loneliness and proteins

In essence, loneliness is a form of physiological stress. It therefore triggers a stress response that alters the body’s molecular processes. The body can even perceive loneliness as a form of threat, releasing hormones that influence immune function, leading to inflammation and disrupting antibody responses. This stress-induced state is also what activates specific proteins. In other words, these proteins are biological indicators of loneliness.

“We know that social isolation and loneliness are linked to poorer health, but we’ve never understood why. Our work has highlighted a number of proteins that appear to play a key role in this relationship, with levels of some proteins in particular increasing as a direct consequence of loneliness,” said Chun Shen from the Department of Clinical Neurosciences at the University of Cambridge and Fudan University in China.

Adrenomedullin (ADM) is a protein linked to loneliness that seems to be particularly important. It can dilate blood vessels in a short period of time, trigger antimicrobial properties and even inhibit bacterial growth, and regulate various endocrine systems. ADM seems to be strongly influenced by loneliness. Another key protein, ASGR1, is associated with higher cholesterol and an increased risk of cardiovascular disease.

Beyond the bloodstream, the effects of social isolation and loneliness extend to the brain. The study connected proteins to changes in brain regions involved in emotion, social processing, and interoception (the sense of the internal state of the body). For instance, higher levels of ADM correlated with reduced grey matter volume in the insula, a region crucial for integrating emotional and social information.

A public health crisis flying under the radar

The findings of this study have far-reaching implications for public health. Firstly, understanding the biological underpinnings of social isolation and loneliness could lead to novel interventions targeting these molecular pathways.

But perhaps even more importantly, these insights suggest the need for social interventions in disease prevention strategies. Programs that foster community connections could have tangible health benefits, potentially lowering the burden of chronic diseases. Your doctor may prescribe to go out more or engage with your local community.

“These findings drive home the importance of social contact in keeping us well. More and more people of all ages are reporting feeling lonely. That’s why the World Health Organization has described social isolation and loneliness as a ‘global public health concern’. We need to find ways to tackle this growing problem and keep people connected to help them stay healthy,” says Professor Barbara Sahakian from the Department of Psychiatry at the University of Cambridge.

For the general public, the main takeaway is that you should take loneliness seriously. It’s not just a fleeting state of mind, it has serious biological impacts. It’s time to prioritize social well-being as a cornerstone of health policy and medical practice.

Journal Reference: Shen, C et al. Plasma proteomic signatures of social isolation and loneliness associated with morbidity and mortality. Nat Hum Behav; 3 Jan 2025; DOI: 10.1038/s41562-024-02078-1