On Sunday or Monday I will write Part Three, which discusses the last part of the Facebook study (“Online Social Integration is Associated with Reduced Mortality Risk“). Having examined the mortality rate of Facebook users (discussed in Part One) and the relative mortality risk of specific Facebook activities (discussed in Part Two), the authors now relate specific Facebook activities to specific causes of death.
I think there will be a Part Four as well; I want to look more closely at the Cox Proportional Hazard Model and a few other details.
For now, I will bring up a problem that has stayed on my mind. Does it make sense at all to compare the dead and the living in this case? We aren’t looking at a disease or harmful exposure. We’re looking at activities of dead Facebook users and living Facebook users. We don’t know how healthy the living Facebook users are; we don’t know whether any of them are at substantial risk for any of the deaths under consideration. It seems highly unlikely to me that Facebook activity (or lack thereof) contributed significantly to any of these deaths or non-deaths. A possible exception is suicide; some sort of contact with the outside world could keep a person from self-destruction, though it could also push someone over the edge. (Not all Facebook interaction is kind.)
Death is polymorphous; it seems to have the same end but has many causes and circumstances. In other mortality studies I’ve seen, there was a similar cause or circumstance. Here, with a stratified sample of living Facebook users and the full group of deceased Facebook users (in California over a two-year period), it seems we’re lacking essential information. The problem is not necessarily with the case control study approach but with the nature of the comparison; the dead and the living may or may not have mortality risks in common.
Another big problem: There’s no way to know, from these data and this study, to what extent any of the effects (real or not) are Facebook-specific. Any Facebook activity might be combined with or influenced by other online activity. The authors do consider a possible relation between Facebook activity and offline activity, but not between Facebook and other online activities.
I will think and write more on this later.