Mental health

Is loneliness contagious?

Scientists have said that people who feel lonely can spread that feeling to others "like a cold", The Daily Telegraph reported. The newspaper said that “lonely people tend to spread their outlook on life to others, and over time the whole group of lonely, disconnected people move to the fringes of society”.

This study will shortly be published in a journal, but drafts of the paper are already available online. The results may advance our understanding of loneliness in general, but the idea that loneliness is“contagious” will need further research.

However, the authors’ suggestion that lonely people should be helped early on is a sound one: "Because loneliness is associated with a variety of mental and physical diseases that can shorten life, it is important for people to recognise loneliness and help those people connect with their social group."

Where did the story come from?

This research was carried out by Dr John T. Cacioppo from the Department of Psychology at the University of Chicago, and colleagues from the University of California and Harvard. The study was supported by National Institute on Aging Grants. A draft was available online at the Social Science Research Network. A peer-reviewed version is due to be published in the medical journal: Journal of Personality and Social Psychology.

The Daily Express also reported this research, and emphasised that loneliness is contagious.

What kind of research was this?

In this social network study, the researchers analysed data from two other cohort studies, called the Framingham Heart study and the Framingham Offspring study. These long-running studies are attempting to identify common factors that contribute to cardiovascular disease in a large group of participants.

The researchers wanted to test the theory that an individual’s perceived social isolation (i.e. loneliness) is linked to the number of connections in their social network (i.e. the number of close friends they have). They particularly wanted to see whether a measure of loneliness within social networks could be seen to spread over time.

What did the research involve?

The researchers derived the social networks from the subjects of the two Framingham studies. The individuals at the centre of each network were called ‘focal participants’ (FP), and were selected from the Framingham Offspring study. The friends and relatives within this person’s network were called ‘linked participants’ (LP). Information about LPs was obtained from both the Offspring study and the original Framingham Heart study.

In all, there were 12,067 individuals in the entire social network supplied by all cohorts in the Framingham Heart Study. Of these, 5,124 were FPs.

Subjects in the Framingham study undergo multiple examinations at predetermined intervals. The measure of loneliness came from a questionnaire depression scale (CES-D) given between 1983 and 2001 at times corresponding to the 5th, 6th and 7th examinations. The participants were asked how often during the previous week they experienced particular feelings, one of which was loneliness. There were four possible answers (0-1 days, 1-2 days, 3-4 days and 5-7 days).

This information was then analysed for associations between FP loneliness and LP loneliness. Influences that might affect this link were also assessed, including age, sex and relationships. Results were displayed as linked clusters on a map, giving a graphical representation of where clusters of loneliness might be occurring.

What were the basic results?

The average number of social contacts (friends and family combined) fell from about four for people who felt lonely 0-1 days a week, to about 3.4 for people who felt lonely 5-7 days a week.

The researchers say that their results indicate that loneliness occurs in clusters within social networks. They say it extends up to three degrees of separation from the FP, meaning that it can be seen in friends of friends of friends.

The idea that loneliness spreads like a contagion was based on the observation that, over time, scores of loneliness seemed to spread to the edge of a network. The spread of loneliness was found to be stronger than the spread of perceived social connections. It was stronger for friends than family members, and stronger for women than for men.

When the researchers drew the connections between people in their ‘cluster map’ those who reported feeling lonely appeared towards the edge of the network. This was confirmed by statistical models discussed in the main text.

How did the researchers interpret the results?

The researchers say that their findings show that loneliness is not only a function of the individual but also features among groups of people.

They argue that the nature of the friendship matters as well, in that LPs who are friends with more than one lonely FP are themselves more lonely. They say that this makes it unlikely that their results were caused by some jointly experienced exposure (for example, a confounding factor).


This study has used a large amount of data from several long-running cohort studies, and re-examined them with the intention of improving our understanding of loneliness. Some of the results and conclusions seem intuitively correct. For example, it is not surprising that people who feel lonely have fewer social connections, and that this would account for their less connected position in the network towards the edge of the researcher’s social map.

What appears to be new in this research is the idea that loneliness is contagious. This is based on the observation of how social relationships change over time. No clear statistics on this are offered in the draft version of the research appraised in this article.

Overall, this study seems to support common assumptions about loneliness. The authors’ suggestion that better social cohesion of lonely people early on is a sound one: "Because loneliness is associated with a variety of mental and physical diseases that can shorten life, it is important for people to recognise loneliness and help those people connect with their social group."

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