Almost every day I check to see what the Science of Us (New York Magazine) writers have posted. Although the quality varies, it’s usually interesting. Some of it I find enlightening, some of it makes me shake my head, and some evokes a combination of reactions. They’re relatively skeptical in their descriptions of psychological research, but sometimes their skepticism seems “token” and safe. It may depend on how much time they have to research and write a given piece.
So after reading Melissa Dahl’s (nominally skeptical) piece about the just-published study in PNAS about Facebook activity and mortality, I vowed to take a close look at the study and give my own take on it. Dahl found it “deeply sad” that the study suggested that a lower mortality risk was associated with friend requests accepted, not friend requests initiated. This seems to suggest (to her) that if you’re trying to reach out to people, you may not be making yourself healthier.
But I found it hard to accept any of this. Why are people associating Facebook “friending” with anything substantial? How is it possible to isolate one Facebook activity from another and measure its relation to mortality, when there are so many other factors at work? Isn’t this a classic case of forking paths–where you can look for all kinds of associations and are bound to find something?
Instead of just criticizing in a void, as I sometimes do, I vowed to read the actual study from start to finish. I suspect it has some serious problems, but let’s see. I want to preface this by acknowledging the good intentions of the authors. One of them, James Fowler, told Dahl, “The whole reason that I’m in this game is because I want to figure out how to use social networks to make people healthier.” In criticizing the study, I do not disparage its underlying intent. Moreover, Fowler himself expressed some caution about the study’s conclusions.
With all of that in mind, here we go. I may have to do this in several parts.
Here’s the citation: William R. Hobbs, Moira Burke, Nicholas A. Christakis, and James H. Fowler, “Online Social Integration is Associated with Reduced Mortality Risk,” PNAS, Early Edition, published ahead of print on October 31, 2016, doi: 10.1073/pnas.1605554113.
In this study, the researchers do two things (boldface added): “Using public California vital records, we compare 12 million Facebook users to nonusers. More importantly, we also look within Facebook users to explore how online social interactions—reflecting both online and offline social activity—are associated with longevity.”
Here’s how the abstract summarizes the results:
The results show that receiving requests to connect as friends online is associated with reduced mortality but initiating friendships is not. Additionally, online behaviors that indicate face-to-face social activity (like posting photos) are associated with reduced mortality, but online-only behaviors (like sending messages) have a nonlinear relationship, where moderate use is associated with the lowest mortality. These results suggest that online social integration is linked to lower risk for a wide variety of critical health problems.
All right, let’s see how they arrived at this. Some of it seems intuitively right (moderate online behaviors, combined with offline behaviors, would be more conducive to health than online-only behavior generally). But hunches aren’t the point here; I want to see how the study fits together.
First, they compared the age- and gender-matched mortality rates of the full population of Facebook users (in California, that is) to the mortality rate in the California voter record. It seemed that the Facebook rate was 63% of the California voter rate, but they recognized that this figure could be off because of the difficulty of matching Facebook users to vital records. So they tried again, this time focusing on the “voter” subpopulation of Facebook users. This time, the Facebook mortality rate was about 88% of the rate of Facebook nonusers (within the voting population).
They then disaggregated this by cause of mortality. They found no difference between the populations for mortality rates due to sexually transmitted diseases, several types of cancer, unintentional injuries, drug overdoses, and suicides. For certain other causes (infections, diabetes, mental illness or dementia, ischemic heart disease, stroke, other cardiovascular diseases, liver disease, and homicide), they found a significantly lower rate in Facebook users.
They acknowledged possible problems with these figures: “It is important not to read too much into the comparison between Facebook users and nonusers because many factors may confound the apparent association between being a Facebook user and experiencing lower mortality. This is an observational result, and we have few socioeconomic controls because we do not have much information about nonusers.”
I give them credit for this. I agree heartily and suspect that economic factors play heavily into the results. Facebook users may have more resources in general, including health insurance. (I suspect that among nonusers, those who abstain from Facebook out of preference or principle are a minority, and that others simply can’t afford certain computer activities. I might be wrong about this.)
In addition, as Fowler said to Dahl, it’s important not to confuse correlation with causation. The mortality rate for Facebook users could be lower because they’re generally healthier when they begin using it; the very ill may be too overwhelmed or incapacitated to use it much.
Now comes the second and more complex part of the study: the analysis of specific Facebook activities and their relation to mortality. I’ll leave that for next time. For now, I don’t think there’s too much we can learn from the first part; the Facebook mortality rate could be lower than the nonuser rate for numerous reasons; there’s no reason to suppose that Facebook helps you live longer. The authors acknowledge this.
Note: I made some minor edits to this piece after posting it.