Open Up the Hood and Check Out the Engine

I was thinking about how I might conceptualize the increase in death rates that Anne Case and Angus Deaton observed last year, so I drew this monstrosity:

causal-model-of-obesity-and-death-rates

The funny thing here is not only that you could add more boxes/potential causal factors ad infinitum, but that it’s awfully hard to rule out one chain of arrows versus another. For example, this picture assumes that the way that social and technological changes increase obesity is by increasing inactivity and changing diet. But there’s a fair amount of evidence that the micro-biome (bacteria in the gut) might affect obesity directly as well as via changed eating and exercise habits, and I even have some crank hypotheses about atmospheric changes affecting obesity and metabolism that I haven’t entirely sworn off.

There’s a lot to be said for the Rubin Causal Model, where you imagine causes as the treatment in an ideal randomized experiment. Thinking in terms of counterfactuals and real-life treatment effects is very useful for sharpening what you mean when you say “X causes Y,” and is at the very least a good guideline for public policy, which is almost always in the business of considering marginal rather than average treatment effects. But there’s a long way from any of those kinds of “causes” to what we mean in our everyday way of asking what causes a social problem. Our ability to notice that the engine of our society is leaking oil or puffing out smoke is considerably ahead of our ability to open up the hood and figure out what is going on.

5 thoughts on “Open Up the Hood and Check Out the Engine

  1. This post reminds me of the debate about the Oregon Medicaid study. Not to sound like a conspiracy theorist, but there is something going on that we only see indirectly as leaking oil and blowing smoke with regards human health that is causing the huge increase in autism, ADD, ADHD, allergies of all types, and asthma. I’m unwilling to pawn it all off on the idea that we didn’t diagnose them before, that a century ago the poor kids just died of unknown causes, and that we over medication of kids to make them docile. A surge of peanut allergies in the 1950s would have been seen and written up in the medical literature of the day, but for some reason it happened in the 1980s and onwards. The allergies have something to do with the microbiome and the immune system, but what, we aren’t exactly sure.

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    1. Yeah, I’m a bit hesitant to give my crank theory about this, but basically I think the online nutters who go on about physiological pH and acid/alkaline balance are exactly right, and that we might be driving our bodies towards acidosis, whether through changes in the atmosphere, too much time indoors in well-sealed houses, or microbiotic changes (as well as obesity/diet/behavioral feedbacks.)

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      1. Physiological pH? That’s a new one on me. The most interesting bit about the allergies that I’ve read, is that farm kids never get them, something about constant prenatal exposure to animals and dirt.

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