Action vs. inaction

by PhilGoetz2 min read30th Nov 200943 comments


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2 weeks ago, the U.S. Preventive Services Task Force came out with new recommendations on breast cancer screening, including, "The USPSTF recommends against routine screening mammography in women aged 40 to 49 years."

The report says that you need to screen 1904 women for breast cancer to save one woman's life.  (It doesn't say whether this means to screen 1904 women once, or once per year.)  They decided that saving that one woman's life was outweighted by the "anxiety and breast cancer worry, as well as repeated visits and unwarranted imaging and biopsies" to the other 1903.  The report strangely does not state a false positive rate for the test, but this page says that "It is estimated that a woman who has yearly mammograms between ages 40 and 49 has about a 30 percent chance of having a false-positive mammogram at some point in that decade and about a 7 percent to 8 percent chance of having a breast biopsy within the 10-year period."  The report also does not describe the pain from a biopsy.  This page on breast biopsies says, "Except for a minor sting from the injected anesthesia, patients usually feel no pain before or during a procedure. After a procedure, some patients may experience some soreness and pain. Usually, an over-the-counter drug is sufficient to alleviate the discomfort."

So, if we assume biannual mammograms, the conclusion is that the worry and inconvenience to 286 women who have false positives, and 71 women who receive biopsies, is worth more than one woman's life.  If we suppose that a false positive causes one week of anxiety, that's a little over 5 years of anxiety, plus less than one year of soreness.

(I heard on NPR that the USPSTF that made this recommendation included representatives from insurance companies, but no experts on breast cancer.  So perhaps I'm barking up the wrong tree by looking for a cognitive bias more subtle than financial reward.)

I'm not shocked at the wrongness of the conclusion; just at its direction.  The trade-off the USPSTF made between anxiety and death is only 2 orders of magnitude away from something that could be defended as reasonable.  Usually, government agencies making this tradeoff are off by at least that many orders of magnitude, but in the opposite direction.  (F-18 example deleted.)

So, what cognitive bias let this government agency move the decimal point in their head at least 4 points over from where they would normally put it?

I think the key is that this report recommended inaction rather than action.  In certain contexts, inaction seems safer than action.

Imagine what would happen if the FDA were faced with an identical choice, but with action/inaction flipped:  Say you have an anti-anxiety drug, which will eliminate anxiety of the same level caused by a false-positive on a mammogram, in 15% of the patients who take it - and it will kill only 1 out of every 2000 patients who take it.  Per week.

Would the FDA approve this drug?  Approval, after all, does not mean recommending it; it means that the decision to use it can be left to the doctor and patient.  The USPSTF report stressed that such decisions must always be left up to the doctor and patient; by the same standards, the FDA should certainly approve the drug.  Yet I think it would not.

A puzzle is why we have the opposite bias in other contexts.  When Congress was debating the bank bailouts and the stimulus package, a lot could have been said in favor of doing nothing; but no one even suggested it.  Empirically, we have a much higher success rate at intervening in health than in economics.  Yet in health, we regulate actions as if they were inherently dangerous; while in economics, we see inaction as inherently dangerous.  Why?

ADDED: Perhaps we see regulation as inherently safer than a lack of regulation.  "Regulating" (banning) drugs is seen as "safe".  "Regulating" the economy, by bailing out banks, passing large stimulus bills, and passing new laws regulating banks, is seen as "safe".  Recommending or not recommending mammograms isn't regulation either way; therefore, we perceive it neutrally.

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