Proofiness - Charles Seife [18]
Legislators around the world still attempt to ban NutraSweet periodically, in part because of its supposed cancer-causing properties. 18 In 2005, a British member of Parliament tried to get “this carcinogenic substance to be banned from the UK food and drinks market altogether.” A state representative in New Mexico tried to ban it in 2006, and one in Hawaii tried in 2009. The fight against NutraSweet—all based on a false belief—will almost certainly continue for years hence. Olney’s causuistry created a belief that will take decades to erase.19
The question remains: if not NutraSweet, what was responsible for the rise in brain tumors? Nobody knows. A guess—and it’s just that, a guess—is that we got a lot better at diagnosing brain tumors in the mid-1980s. In 1984, there were 108 MRI machines in the entire United States. These machines are particularly good at finding problems in soft tissue, like the brain. In 1985, the number more than tripled, increasing to 371. At the same time the government started approving MRI scans for Medicare patients. It’s quite possible that the new diagnostic tool allowed doctors to catch more brain tumors all of a sudden. Just as it’s important to take the changing value of a dollar into account when comparing spending over time, it’s important to take doctors’ changing diagnoses into account when looking at disease trends. (To be fair, Olney attempted to do this, but his analysis was unconvincing.)
A change in diagnostic criteria can look just like an epidemic. Doctors, for example, are much more likely to diagnose autism today than they were twenty or even ten years ago. As clinicians have become more aware of the condition, and as the criteria for diagnosis have changed several times since 1980, it’s hard to tell if there’s a real rise in autism or whether doctors now have a single name for something that was called a variety of things before, making for an easier diagnosis. In a 2002 study, researchers discovered that California showed a threefold rise in autism diagnoses over a seven-year period. However, over the same period there was a corresponding decrease in the diagnosis of undifferentiated “mental retardation”—suggesting that the rise is due to the labels that doctors put on a disease, rather than any change in the children who are being born. The jury’s still out, but it’s by no means clear that there really is an epidemic of autism.
The perception is enough—once people think there’s an epidemic, they try to find something to blame. Causuistry is their primary weapon. With the perceived autism epidemic, many people point their finger at vaccines—either the measles-mumps-rubella (MMR) vaccine or a mercury-based preservative that was used in some vaccines. Activists such as former Playboy model Jenny McCarthy have launched a blistering causuistry-based attack that is causing parents to question whether they should get their children vaccinated. The antivaccine activists note a correlation: children develop autism after they’re vaccinated. Yet there’s no causation there; in fact, there’s plenty of evidence to the contrary. (For example, the rising number of autism diagnoses that predate the MMR vaccine’s introduction in 1988 argues against an MMR-autism link; the preservative-autism link is undermined by the fact that Denmark’s autism incidence keeps rising even though the preservative was phased out in 1992.) Blaming vaccines for autism is nothing but causuistry.
It’s always difficult to differentiate causes from effects; it’s hard to look at a set of data and come up with convincing evidence that event A is causing effect B. Sometimes common sense tells us that A and B aren’t directly related at all—yet the pages of peer-reviewed journals are filled with silly-sounding “discoveries” of linkages that wither under the harsh light of logic. In 1996, for example, sociologists argued that women with larger hip-to-waist ratios gave birth to a larger proportion of sons than daughters, perhaps explaining why men in