It’s not often I see something positive in Dr Leaf’s work, but today was one such occasion.
I’m often (legitimately) critical of Dr Leaf’s paucity of references and citations for her Facebook posts and social media memes. Today was different – Dr Leaf made a statement and backed it up with an easily obtainable peer-reviewed journal article. It’s a shame it wasn’t backed up by an accurate interpretation, but it’s a positive step none-the-less.
Dr Leaf claimed that “People who served others experienced a 68% increase in healing compared to those who only got treatment for themselves.”
Since the article was so easy to find, I decided to look it up. The article was by Poulin et al, “Giving to others and the association between stress and mortality”, in the American Journal of Public Health . Actually, the article was familiar, because Dr Leaf has written about the same article before, but her social media post that time was more nebulous.
So does the study by Poulin and his colleagues show that people who served others experienced a 68% increase in healing compared to those who only got treatment for themselves? In a word … no.
First of all, the study wasn’t looking at healing, it was looking at mortality. They may seem similar, but getting better from something (“healing”) is not the same as not dying from something (“mortality”).
Second, no one in the study was being “treated”. I’m not sure where Dr Leaf got the idea that the control group was getting “treatment”. The study compared those who self-reported “helping behavior directed toward close others … in any of 4 unpaid helping activities directed toward friends, neighbors, or relatives who did not live with them” versus those that did not.
Thirdly, there’s no mention of a 68% improvement anywhere in the article. The article gives its results as hazard ratios. For the non-statisticians, the hazard ratio is “the ratio of the particular event taking place in treatment group compared to control group.” The simplest (probably over-simplified way) way of thinking about hazard ratios is to do a simple sum – the hazard ratio minus 1 is the percentage increase or decrease in risk, where a positive number is an increased risk and a negative number is a decreased risk. So a hazard ratio of 1.13 means that a person in the exposure group has a 13% increased risk compared to the control group (=1.13 – 1). And a hazard ratio of 0.7 means a 30% decreased risk (0.7 – 1 = -0.3). So for the helping group to have a 68% decreased risk of dying, the hazard ratio would be 0.32 (0.32 – 1 = -0.68).
If you’re lost in the numbers, don’t stress. The point is that Dr Leaf was very specific about the helping group increasing in healing by 68%, but there’s nothing in the results to suggest this. The study authors wrote, “When we adjusted for age, baseline health and functioning, and key psychosocial variables, Cox proportional hazard models for mortality revealed a significant interaction between helping behavior and stressful events (hazard ratio [HR] = 0.58; P < .05; 95% confidence interval [CI] = 0.35, 0.98). Specifically, stress did not predict mortality risk among individuals who provided help to others in the past year (HR = 0.96; 95% CI = 0.79, 1.18), but stress did predict mortality among those who did not provide help to others (HR = 1.30; P < .05; 95% CI = 1.05, 1.62).” Unless I’m missing something, there’s nothing in the results that remotely suggests a 68% improvement in anything.
And for what it’s worth, the study shows very weak associations anyway (in statistical terms, the confidence intervals are broad, and almost cross 1), so even if the study really did say something about a “68% increase in healing”, it’s something that is only slightly more likely to occur than by chance alone. Then there’s other evidence that contradicts this particular study’s findings, so in all fairness, this study shouldn’t be used to base social media memes on in the first place.
Overall, it’s good that Dr Leaf cited an article in her social media meme, but her interpretation of the study was poor, something more at the level of a university freshman than a supposed expert in her field. And it reflects badly on the Christian church that this is the level of ‘expertise’ that the church accepts and then promotes.
I would encourage Dr Leaf to continue to cite references for her memes, but she really needs to learn how to interpret clinical studies if she and the church are going to continue to promote her as some sort of expert.
 Poulin MJ, Brown SL, Dillard AJ, Smith DM. Giving to others and the association between stress and mortality. Am J Public Health 2013 Sep;103(9):1649-55.