Two things jump out immediately: - a bayesian mixed model is just what I would have used here, great choice and a good sign for power - the effect sizes are d

Two things jump out immediately: - a bayesian mixed model is just what I would have used here, great choice and a good sign for power - the effect sizes are definitely very small. I would not overstate the story here. That said, I also don't believe that facebook is the primary story here, because other findings all suggest tiny effect sizes (see the famous emotional contagion experiment) and because we don't have a clear, convincing theoretical model IMO. There are just so many intra-individual confounders that would need to be included, including some that have dynamic, self-reinforcing effects. Still, great to have more robust work here. [edit] PS: just to throw a methodological nitpick out: Some bayesians are going to have a heart attack while reading "the uncertainty cutoff of 97.5% for posterior probabilities".