This paper made me go and have a look at my facebook stats. The average person in the cohort study had 300 facebook friends: I have under 70. I cannot access my like statistics: I need to recite number 12 of the 16 points and not care what people think of me.

Because facebook is probably physically harmful to you.

In our cross-sectional multivariate analyses, we found that for each 1-standard-deviation increase in lifetime Facebook likes, a person’s self-reported physical health status decreased by 8% of a standard deviation. In the prospective model, most of these associations lost significance, with the exception of lifetime like count and 30-day link count, both of which were still significantly associated with diminished self-reported physical health. Each 1-standard-deviation increase in lifetime like count in wave t was associated with a decrease of 5% of a standard deviation in self-reported physical health in wave t + 1, and each 1-standard-deviation increase in 30-day link count in wave t predicted a decrease of 4% of a standard deviation in self-reported physical health in wave t + 1 after we controlled for physical health in wave t and all demographic control variables.

Holly B. Shakya, Nicholas A. Christakis; Association of Facebook Use With Compromised Well-Being: A Longitudinal Study, American Journal of Epidemiology, Volume 185, Issue 3, 1 February 2017, Pages 203–211, https://doi.org/10.1093/aje/kww189

An editorial in this month’s Acta Psychiatrica Scandinvica adds more data points. As usual, I have removed the citations, but the link is public access.

In a recent longitudinal study based on three ‘waves’ of data (2013, 2014, and 2015) from more than 5000 participants in the nationally representative Gallup Panel Social Network Study, Shakya and Christakis found that the use of Facebook (which was measured objectively) was negatively associated with self-reported mental well-being. Both clicking ‘like’ on the content of others’ Facebook pages and posting ‘status updates’ on one’s own Facebook page were negatively associated with mental well-being. Importantly, these results were robust to two-wave prospective analyses suggesting that the direction of the effect goes from Facebook use to lower mental well-being and not the other way around. However, due to the observational nature of the analyzed data, these results do not represent causal evidence of a harmful effect of Facebook, but probably—due to the longitudinal nature of the study—represent the best available estimate of the effect of Facebook on mental well-being to date. Another recent study supporting that Facebook use could have a negative effect on well-being is that of Tromholt in which the 1095 participants were randomly assigned (or rather randomly urged) to follow one of two instructions: (i) ‘Keep using Facebook as usual in the following week’, or (ii) ‘Do not use Facebook in the following week’ . After this week, those assigned to the Facebook abstinence group reported significantly higher life satisfaction and more positive emotions than those assigned to the ‘Facebook as usual’ group [5]. However, due to the unblinded design of this study, its results do not represent causal evidence of the effect of Facebook either—an effect, which will be difficult to establish.

If we nevertheless assume that Facebook use indeed has a harmful effect on mental well-being, what is then the mechanism underlying it? This aspect remains unclear, but an intuitively logical explanation—with some empirical support—is that people predominantly display the most positive aspects of their lives on social media and that other people—who tend to take these positively biased projections at face value—therefore get the impression that their own life compares negatively to that of other Facebook users [7]. As indicated by the recent findings by Hanna et al., such upward social comparison is very likely to mediate the negative effect of Facebook use on mental well-being.

It is much better to have a walk. Which I will now do.