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The story behind a spectacular finding:
Loneliness could be a direct cause of type 2 diabetes

A decade of thinking about loneliness led to a discovery with international implications.

It all started when Roger Ekeberg Henriksen noticed a mysterious connection: If you are shy, you catch colds more easily. Now a similar finding means that publications ranging from Newsweek to Hindustan Times have been writing about him.

On 30 September, Diabetologia, a periodical about diabetes, published the astounding finding of Henriksen and his two fellow researchers, Roy Miodini Nilsen and Ragnhild Strandberg, all three from the Western Norway University of Apploed Sciences (HVL).

Their research showed that loneliness could be a direct cause of type 2 diabetes, one of the 10 deadliest diseases in the world.

The risk factor is on par with other typical risk factors, such as poor diet and insufficient physical activity.

A solid finding

Initially, the notion that a lack of good social relationships could be so directly connected to serious illness felt like an audacious hypothesis when Henriksen formed it 10 years ago. But the finding is solid and leaves no room for doubt. It is also closely related to other findings that he has made in recent years as a nursing researcher.

"What happens in our bodies when the soft values, such as social relationships, are neglected is life-threatening. In our research, we can see what this leads to in terms of shorter lives, through fatal conditions such as heart attacks and diabetes," Henriksen says. "In other words: The soft values are actually very hard. Death and ruination follow if we do not take care of them. So it is high time that we as a society take them more seriously than we do today."

A lonely researcher into loneliness

The periodical’s editors had already realised that this finding was going to be noticed, and they sent out a press release internationally.

The response was enormous: Henriksen has already featured in two of the biggest newspapers in India: Times of India and Hindustan Times. The American Newsweek has written a detailed article about the discovery, and he has been interviewed by Medical News Today – one of the biggest medical publications in the world, with 120 million readers every month.

International professionals with millions of followers have been tweeting the news.

"It is vital to get the message that loneliness can make you ill out to as many people as possible, so it feels amazing to be reaching out to millions of people. The fact that two of the biggest newspapers in one of the world’s most populated countries have written about the issue makes me really happy," Henriksen says.

Of course, you have to be exposed to a virus in order to catch a cold or develop influenza. How can a virus care whether you are shy? I was very surprised!

Roger Ekeberg Henriksen

He has seen his name in print in unexpected places like The Spirit of Cape Verde, Nigeria Post and on Reddit’s hot list, as well as a wide range of media in China, Japan, France, Spain, Greece, Australia and Canada – to name a few. An acquaintance with Italian relatives told him that an article about his research even appeared in a local newspaper in Italy. In Norway, the broadcasting company NRK has been reporting on the case.

So why is this finding attracting so much attention?

Henriksen thinks it is because it goes against so much of the way we think about health. On the one side, we have mental health, and on the other side we have physical health, and there is a kind of wall between these fields.

The finding combines knowledge from psychology, medicine and neuroscience, which in itself is unusual, although there are pioneering research communities in the USA, UK and Netherlands that have given him a great deal of support.

Psychologists tend to focus on loneliness, while medical professionals rarely do – at least not in a research context.

"I have felt very lonely researching this subject in Norway," Henriksen says.

The finding that loneliness can make you sick was punlished in the media worldwide.

Connection between psychological phenomena and illness

Every now and then, research involves turning accepted ideas on their head. And that is how it was in this case: ‘Social baseline theory’, on which Henriksen’s research is based, represents a major leap in the way we understand the significance of social relationships for us as humans.

He discovered his theory by chance.

As a nursing student, Henriksen developed an interest in the connection between psychological phenomena and illness. For his Master’s thesis, he looked into shyness.

To his own surprise, his intuition led to some very specific findings: If you are shy, there is a much greater chance that you will catch a cold, develop influenza or suffer from headaches. He published his findings in School Psychology International, but even he found them mysterious.

"Of course, you have to be exposed to a virus in order to catch a cold or develop influenza. How can a virus care whether you are shy? I was very surprised!" he says.

Loneliness leads to changes in blood sugar level

So how can a psychological feeling lead to physical illness? He continued to mull this question over after he had finished his Master’s thesis.

Then he heard of an international health conference in the Netherlands, which would be attended by researcher James A. Coan, professor in psychology at the University of Virginia. Frode Thuen at the HVL suggested to him that this could be right up his street. At the time, Henriksen was working in a medical centre as a talk therapist for children and young people.

He travelled to the Netherlands at his own expense.

The theory that Coan is famous for developing, ‘social baseline theory’, describes the specific mechanisms that form the basis of the findings that Henriksen has since made. But although he heard Coan’s lecture in the Netherlands, it took a while for him to understand its content. He had to learn more about neuroscience and internal medicine in order to understand it.

It was only when they met two years later that Henriksen and Coan talked about one of several hypotheses that could be developed from his theory: That loneliness leads to changes in blood sugar level.

This had not yet been properly tested, but Henriksen wanted to do this with the help of the extensive medical registers that are available in Norway. The American research colleague was enthusiastic about the fact that someone wanted to explore a branch of his theory in depth.

For Coan himself, understanding the connection between health and social relationships was a big leap.

We need each other the way fish need water

What do we mean to each other? How important is it really for a person to have friends, family, a partner, colleagues and neighbours who we greet in passing?

For a long time, the interpretation of researchers involved in stress and health research was that social support was a type of resource that you obtained externally. In other words, it was an extra benefit, something that could give you a boost in life.

But when James A. Coan started looking more closely into this, he discovered that something was not quite right.

In his laboratory, he worked with 10–30 participants and looked at what happened in their brains when they received social support. His expectation was that it would have an activating effect, in line with the view that social relationships were a benefit. But that is not what happened – social support did not trigger any noticeable brain activity.

In fact, the opposite happened: The parts of the brain that control the stress response became less active. Coan was initially shocked that the result was not what he had been expecting.

But when he later discussed this with colleagues whose work involved animal experiments, something fell into place for him. They pointed out that what happens to humans also happens to horses.

"If you remove a horse from its herd, it becomes stressed and anxious, its movements jumpy and capricious. But if it is allowed to rejoin the herd, it relaxes and its behaviour normalises," Henriksen says.

In other words, like horses, we humans need our herds. Social relationships are absolutely fundamental for us to be able to function. They are not some kind of extra benefit, something nice to have. They are something that we must have – if not, it could be dangerous.

"We are able to function well, provided that we are in a mutually supportive social environment. But if that is absent, the stress response in our body is activated immediately," Henriksen says.

He explains that in ‘social baseline theory’, the basic idea is that our brain does not regard social support as a resource, just as a fish in water does not consider the water to be a resource.

"Our brain expects the social support to be in place, just as the fish expects the water to be there," he says.

Loneliness takes a lot of energy

Being lonely therefore means being out of balance: You do not have other people to lean on.

Your brain realises this. It thinks: “I now have to activate my defences and if something dangerous happens, I must be ready to take care of the situation myself.” It starts initiating the body’s stress response: raising the blood sugar level, blood pressure and heart rate, among other things.

"Imagine that you are alone in a dark street at night. You are extra vigilant and expend a lot of energy looking out for possible dangers. That is what it is like for our brain when we feel lonely," Henriksen says.

For Coan, who performed laboratory tests on small numbers of people, it was possible to demonstrate that changes take place in our brain and body as a result of loneliness, but not that these changes lead to illness in the long term.

Facts from Norwegian medical studies

Henriksen had an advantage here – access to extensive health registers in Norway, like the Trøndelag Health Study (HUNT). He wanted to test his ideas about a connection between loneliness and illness on a large scale.

Coan had seen that social isolation led to higher blood sugar levels in the body. But it was a big leap to go from there to claiming that loneliness could lead to an illness like diabetes. From a biological perspective, there was a great deal to explain, and initially this was pure speculation.

Henriksen has taken this leap with his new findings.

He presented his model for the first time when he was a PhD candidate in 2012. It then took 10 years to go from hypothesis to results, because he had to wait for the necessary data to be collected and analysed.

"I needed the results of blood samples from many thousands of people, and as an individual researcher, you just cannot come up with the money for that," he explains.

The data he needed was collected between 2017 and 2019 as part of HUNT. When tens of thousands of blood samples had been analysed in 2020, Henriksen put everything else aside to look at whether the connection he had suspected between loneliness and type 2 diabetes really existed. When Henriksen’s findings were recently published and became known all over the world, Coan, the father of ‘social baseline theory’, was very excited.

"This now shows something that he has also been focusing on for many years: How serious it is to be alone – whether that involves loneliness, social isolation or the feeling of being an outsider. This is a state that we are not anatomically designed for, as a species. Eventually it makes us ill. So we must integrate this knowledge into the entire health system,” Henriksen says.

Inspired by In the House of Angels

The finding about diabetes is not the first for which Henriksen has shown this connection.

He has already shown that loneliness can lead to metabolic syndrome, a condition that lies behind fatal illnesses such as heart attacks.

In another study, he has shown how pregnant women who do not have social support from their partners give birth to children who are at greater risk of catching infectious diseases.

As a nursing student, he was first inspired to perform research into social relationships when he saw In the House of Angels – a film by Margreth Olin depicting the loneliness and isolation of elderly people in care homes. It made a deep impression.

"I saw so clearly then how important a nurse’s role is. But I also thought: Who will take this seriously? Who will prioritise these values, when budgets must be planned and other prioritisations need to be made?" he asks.

Henriksen realised that documentation and hard facts were needed. This has been his project throughout his career as a nursing researcher. Over and over again through the years, he has shown that the soft values and actions have a major impact on very hard outcomes like life and death – on the major public health challenges that we struggle so much to do something about.

"As a male nursing student, I noticed something that was almost intangible: You do things softly, the way women do things. Maybe that triggered me. I saw how important it was, this care, and the entire thinking behind the nursing profession," says Henriksen. "I hope and believe that the research I have performed since has helped to give weight to these values. The next big step now is to find out how to reduce loneliness in society. That is what I will be working on from now on."


Henriksen et al. Loneliness increases the risk of type 2 diabetes: a 20 year follow-up – results from the HUNT study, Diabetologia, 2022. DOI: 10.1007/s00125-022-05791-6

This article/press release is paid for and presented by the Western Norway University of Applied Sciences (HVL)

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