Category Archives: framingham heart study

Loneliness contagious? An oxymoron? (UPDATED 5/2013)

It seems contradictory.  How can the lonely (who are largely outside of social networks) get their loneliness through social networks?

It makes sense when you think of people’s movements in social networks over some period of time.  The lonely may not always have been lonely, but gradually, they tend to cluster together on the periphery of social networks, suggesting that the social connections with other lonely people exacerbates any de facto loneliness they experience.  That the lonely would be somewhere on the periphery of social networks is somewhat tautological, but that the lonely would cluster together at the periphery is not, and is surprising.

The study is by well-respected researchers (psychologist John Cacioppo from U. Chicago, Nick Christakis from Harvard’s School of Public Health, and James Fowler, a political scientist at UCSD) and will appear  in the December issue of the Journal of Personality and Social Psychology.

The Washington Post notes:

Although the study did not examine how loneliness spreads, Cacioppo said other research has provided clues. People who feel lonely tend to act in negative ways toward those they do have contact with, perpetuating the behavior and the emotion, he said.

“Let’s say for whatever reason — the loss of a spouse, a divorce — you get lonely. You then interact with other people in a more negative fashion. That puts them in a negative mood and makes them more likely to interact with other people in a negative fashion and they minimize their social ties and become lonely,” Cacioppo said.

[The research comprising almost 5,000 people  interviewed every two years between 1991 and 2001] showed that having a social connection to a lonely person increased the chances of developing feelings of loneliness. A friend of a lonely person was 52 percent more likely to develop feelings of loneliness by the time of the next interview, the analysis showed. A friend of that person was 25 percent more likely, and a friend of a friend of a friend was 15 percent more likely.The effect was most powerful for a friend, followed by a neighbor, and was much weaker on spouses and siblings, the researchers found. Loneliness spread more easily among women than men, perhaps because women were more likely to articulate emotions, Cacioppo said.

The researchers said the effect could not be the result of lonely people being more likely to associate with other lonely people because they showed the effect over time. “It’s not a birds-of-a-feather-flock-together effect,” Christakis said.

See “Feeling Lonely?  Chances Are You’re Not Alone” (Washington Post, Rob Stein, 12/1/09)

See also blog posts on the contagion effect of happiness, smoking, and obesity.

See article “The Science of Loneliness” (New Republic, Judith Shulevitz, May 2013)

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Happiness is contagious

dancingfriendsNick Christakis (Harvard School of Public Health) and James Fowler (Univ. of Calif., San Diego), who previously used the Framingham Heart Study to show that having fat friends increasingly makes people obese, are back with a very interesting paper showing that happy friends make you happy — what the co-authors called ‘an emotional quiet riot’.

It is already established that happiness and having social capital (friendships) are linked, but this research demonstrates that it matters how happy your friends are and that it is the happy friends that are causing your happiness rather than vice versa. Conversely, having unhappy friends over time makes you less happy.

The research shows up in the latest issue of BMJ. “Dynamic spread of happiness in a large social network: longitudinal analysis over 20 years in the Framingham Heart Study.”  [The study involved 5,124 adults aged 21 to 70 who were followed between 1971 and 2003.]

They measured happiness with a 4-item construct:  “I felt hopeful about the future”; “I was happy”; “I enjoyed life” and “I felt that I was just as good as other people.”

They found that happiness is a network phenomenon, clustering in groups of people that extend out to 3 degrees of separation (the friends’ friends of one’s friends), but with greater impact on friendships that are 2 or 1 degree of separation from you.  Demonstrating the magnitude of this effect, co-author James Fowler noted, “if your friend’s friend’s friend becomes happy, that has a bigger impact on you being happy than putting an extra $5,000 in your pocket.”

They found that happiness spreads across a diverse array of social ties, from spouses to siblings to neighbors. They found no happiness effect of co-workers and found that nearby ties had a far greater influence than distant ties: for example, knowing someone who is happy, makes you 15.3% more likely to be happy, but having happy next-door neighbors makes you a full 34% more likely to be happy (much higher than having happy neighbors merely on your block). The optimal effect was for a happy friend living less than half a mile away, which boosts your chance of happiness by42%. In one of the study’s surprises, happy spouses (which one assumes live less than a half mile away!) only increased one’s chance of happiness by 8%. Part of the lower spouse effect is that happiness spreads more effectively through same sex relationships than relationships (romantic or not) between a man and a woman.  (Gays take note!)  Christakis and Fowler believe we may take emotional cues from people of our gender.

They observed that network characteristics (where you were in the network and how happy the people were around you) could independently predict which individuals would be happy years into the future.

They suggest that there may be an evolutionary basis for human emotions.  Previous work noted that emotions like laughter or smiling seemed evolutionary adapted to helping people form social bonds.  [They note: “Human laughter, for example, is believed to have evolved from the ‘play face’ expression seen in other primates in relaxed social situations. Such facial expressions and positive emotions enhance social relations by producing analogous pleasurable feelings in others.”]

While they couldn’t prove it, they suggested 3 possible causal mechanisms:

  1. happy people might share their good fortune
  2. happy people might change their behavior toward others (by being nicer or less hostile)
  3. happy people might exude a contagious emotion (although this would have to be over a sustained time period)

Christakis and Fowler noted that the 3-degrees of separation impact observed in happiness was the same as for smoking and obesity (which also reached out 3 degrees). They wonder whether a “3-degrees of influence” extends to behaviors like depression, anxiety, loneliness, drinking, eating, exercise and other health-related activities.

So the next time you’re unhappy realize that you may be “infecting” your friends with unhappiness as well.  Christakis’ work is suggesting that we need friends, but we also need to carefully pick friends that are happy and have healthy behaviors or we risk that their unhappiness and unhealthy behaviors will spread to us.  The New York Times notes that one of the co-authors indicated that he now thinks twice about his mood knowing that it affects others. That said, he noted: “We are not giving you the advice to start smiling at everyone you meet in New York….That would be dangerous.”

While they think that face-to-face connection is important in spreading happiness (hence the decline of these effects with distance), they did a separate study of 1,700 Facebook profiles, where they found that people smiling in their photographs had more Facebook friends and that more of those friends were smiling. While the Facebook study is just an initial foray into the online word, Christakis thinks that it shows that some of these happiness findings might extend on social networking as well.  And it would take longitudinal studies to determine whether our online activities are gradually eroding our need for face-to-face communication to spread happiness.

Note: Justin Wolfers (on the Freakonomics blog) is skeptical of this research.  As he notes:

[It’s possible that it is not your friends’ happiness that is causing yours, but that “if you and I are friends, we are often subject to similar influences. If a buddy of ours dies, we’ll both be less happy. Or, less dramatically, if our favorite football team wins, we’ll both be happier. But this isn’t contagious happiness — it is simply a natural outcome of the shared experiences of people in the same social circles. Unfortunately, observational data cannot distinguish the headline-grabbing conclusion — that happiness is contagious — from my more mundane alternative: friends have shared emotional influences.”

Wolfers notes that a very careful article by Ethan Cohen-Cole and Jason Fletcher uses the same research design to show how it can lead to silly conclusions.  Cohen-Cole and Fletcher find in another dataset that this approach shows “height, headaches, and acne are also contagious.” As Wolfers notes, it’s more likely that “the same jackhammer causing your headache is likely causing mine.” And the height finding is obviously not causal but more likely a function of homophily (people choosing similar friends).

See Clive Thompson, “Is Happiness Catching?” (NYT Sunday Magazine, 9/13/09)

Boston Globe story available here.

New York Times story available here (which also has a nice graphic showing the clustering in this network of happy and unhappy people).

L.A. Times story available here.

See Wolfers’ Freakonomics blog post here.

Can your friends affect your weight?

Nicholas Christakis (at the Harvard School of Public Health) (together with James Fowler at U. Cal. San Diego) has done very interesting research with the landmark Framingham Heart Study looking at the likelihood of obesity. They find, after tracking some 12,000 individuals through the 32-year long study (1971-2003), that even controlling for all the genetic markers for obesity (like parents’ obesity) and weight at the study’s baseline, having fat friends increases the chance that you will be fat.  [The Framingham study participants could list only up to 3 friends, so the friends being discussed here are closer, stronger friends, rather than weaker ties.]

Having an obese friend increased one’s likelihood of obesity by 57%, with a smaller effect for siblings and spouses. This risk of developing obesity rose to 171% for the closest mutual friendships. Having very large neighbors had no effect on obesity if those neighbors weren’t friends of the individual in question.

The study found that the network impact of friends on obesity could be seen in as small as 2-4 year increments.

Christakis discounted other likely factors such as environmental (since it didn’t matter how close geographically ones’ friends were, making it less likely that they are both responding to something in the neighborhood, for example).  They did code the data for density of fast food restaurants and it did not make this effect go away.  [The fact that long-distance close friends influence obesity as much as nearby close friends is very surprising;  for sure, if respondents are still listing this long-distance friend as one of their three closest friends, they must have stayed in regular contact, but I would have thought that obese friends made respondents feel more comforable being obese partly by physically seeing an obese friend, and this is presumably less common with geographically distant friends.

And Christakis thinks the mechanism is “induction”; having an overweight person list YOU as their friend doesn’t increase your likelihood of being obese, but your listing an overweight person as YOUR friend does.  The impact of these friendships decreases with social distance (in other words, your friends affect your weight more than your friends’ friends, which is more consequential than the weight of your friends’ friends’ friends, etc.) but they still have an impact out to three degrees of separation.  And same sex friends influence your weight gain more than opposite sex friends.

Christakis thinks that people with heavier friends either come to think of themselves as less fat or else it validates their obesity in a way that wouldn’t be the case if their friends were thinner.  (But the study showed that it wasn’t the simple story of a change in physical exercise or eating habits from these friends.)  And there is homophily in obesity — in other words, fat people are more likely to choose overweight friends and thin people are more likely to pick thin friends.  And if overweight people have thin friends or vice-versa, these relationships tend to be less stable over time (the thin people are more likely to drop their overweight friends or become more obese).

The New York Times notes that: “Science has shown that individuals have genetically determined ranges of weights, spanning perhaps 30 or so pounds for each person. But that leaves a large role for the environment in determining whether a person’s weight is near the top of his or her range or near the bottom. As people have gotten fatter, it appears that many are edging toward the top of their ranges. The question has been why. ” (“Find Yourself Packing It On? Blame Friends, NYT, 7/26/07).  The study suggests that social contagion of obesity through networks may be the explanation.

Christakis thinks that the role of social networks may be one of the explanations for the increasing obesity in America (along with other factors like exercise, change in eating habits like supersizing of food and more fast food and soft drinks, etc.).  The social networks may have changed norms and made weight gains more acceptable, even outside of any change in behavior.    Moreover Christakis thinks that we might be able to use the structure of social networks to fight obesity, by for example fighting obesity in groups rather than with individuals.  If there can be a social contagion of obesity, how might we start a social contagion of weighing less?  Co-author James Fowler noted that having a friend that was able to lower his or her weight down made it easier for one to lose weight; that’s why weight loss programs often function using groups, to reinforce the attempted change in behavior. But this question of spurring a social contagion for good is exactly the kind of question that Malcolm Gladwell in The Tipping Point considers.

Christakis and colleagues have also found similar network properties in this study to the spread of smoking, but the cessation of smoking was not a factor in individuals gaining weight or not.

Finally Christakis thinks that we may undervalue health interventions since we look only at the impact of the intervention on one individual rather than examining the multipliers on this investment through his/her social network.

The authors note that there are many social and health benefits of  friendship so their study is not a reason not to develop friends with anyone.

Follow-up posts on this study available here, and here.

The Christakis et al article is published today in the New England Journal of Medicine and a summary of some of the findings is available in this Harvard Gazette story.

There’s a neat visual representation of the obesity spreading through the social networks over time in this video.

See also, Clive Thompson, “Is Happiness Catching?” (NYT Sunday Magazine, 9/13/09)