The complicated role loneliness plays in 26 common health conditions

The idea that loneliness leads to certain health conditions is now being called into question. Although loneliness is associated with a range of negative physical health outcomes, including an increased risk of premature death, it might just be correlated with many of the conditions it was previously assumed to cause.

“Loneliness seems to act as more of an indicator of disease rather than a direct cause,” says Jihui Zhang at Guangzhou Medical University. “Instead, socioeconomic factors, lifestyle choices and genetic predisposition might be driving risk for diseases like diabetes and heart diseases.”

Social connection is essential to our mental health and ability to thrive. Yet loneliness – the painful feeling that arises from social disconnection – affects a growing number of people around the world.

To learn more about how this affects health, Zhang and his colleagues analysed data from several biomedical databases, including the medical information of 476,100 people in the UK, 16,000 in China and 14,000 in the US. They found that participants who reported feelings of loneliness were at a higher risk of 30 out of 56 individual conditions, ranging from cancers to digestive system conditions.

Then the researchers performed a second round of statistical analysis on 26 of those 30 conditions, focusing on the subset of participants whose genetic data was available. The results revealed that most of the conditions were not, in fact, caused by loneliness. These health problems, including cardiovascular disease, obesity and type 2 diabetes, merely occurred alongside loneliness. But loneliness could still potentially play some role in causing six of the conditions: depression, hypothyroidism, asthma, sleep apnea, substance abuse and hearing loss.

According to Yu He, also at Guangzhou Medical University, the findings have important implications for real-world interventions. “Addressing loneliness is important, but it’s not the only factor in preventing diseases,” she says. “Public health authorities should also focus on improving mental health services and promoting healthy lifestyles.”

David Sbarra at the University of Arizona says the new study “should give us pause in how we think about the public health goals of reducing loneliness to improve human health”.

“To be sure, loneliness itself is highly aversive and seems to be causally associated with the emergence of depressive episodes, but in terms of the connection to health, some of the most cherished findings in the field need to be reconsidered,” says Sbarra. “It is important to understand where the causal effects might exist and where the correlations seem to exist.”

Zhang, He and their colleagues are planning to investigate the underlying biological mechanisms behind their findings, including how loneliness affects things like stress hormones and inflammation. They also hope to run studies on groups of people from other parts of the world to see if their current findings – which are predominately based on data from people in the UK – hold up.

Sbarra adds that, to truly determine whether loneliness causes certain conditions, researchers will need to study whether having better social connection leads to health improvements. “Obviously, any intervention studies showing that you can improve health markers by reducing loneliness would be truly remarkable,” he says. “We have very few examples suggesting this is indeed possible.”