The causation fallacy

Original image from
Original image from

The year was 1952, Elizabeth II was queen and Richard Doll couldn’t ignore the math anymore.

The epidemiologist had spent five years poring over the cases of hundreds of lung cancer patients — 709, to be precise — in twenty hospitals scattered across London, pulling his hair out to link their diseases together to a likely cause. At first, he thought it might be this newfangled material, tarmac; but upon further study, it became increasingly obvious that there was one link. Cigarette smoking was the most common factor, and that presented a problem.

In 1952, the tobacco industry was booming. Advertisements appeared in almost every magazine, which splashed from the coffee table of almost every housewife and from the newsstands on the commutes of most men. Cigarettes were an omnipresent character in the backdrops of movies, music, restaurants, trains, sporting events and business meetings. If anything was a cultural icon in America and Britain for decades, it was the cigarette.

Doll, an Englishman, had made a career in epidemiology nearly as illustrious as his predecessor, John Snow (of the Broad Street water pump experiment fame, not Game of Thrones). However, flying in the face of a dominant and powerful industry such as tobacco must have been a terrifying prospect. His research, published in the British Medical Journal in 1952, betrayed no anxiety:

“To summarize, it is not reasonable, in our view, to attribute the results to any special selection of cases or to bias in recording. In other words, it must be concluded that there is a real association between carcinoma of the lung and smoking.”


The consequence of this and the subsequent report in 1964 from the U.S. Surgeon General, which cemented the federal health policy about the correlation between smoking and lung cancer, is still being debated today.

A recent study from Stanford fellow Robert Jackler, found that six otolaryngologists– ear, nose and throat specialists– had received massive payments from tobacco companies to testify against cancer patients. They are likely not the only ones, and this is likely a sign that many plaintiffs lost cases on faulty evidence, he wrote in the study, published July 17 in the journal Laryngoscope.

Jackler studied the documents released through litigation against tobacco companies in recent years to observe the connections. Correspondence files, internal memoranda and payment records revealed the patterns of payments and coaching that these physicians went through to support the tobacco companies. One received $100,000 for a single case; another’s opinion was written by a tobacco company lawyer and signed by her.

18 months of reading these documents and comparing them to existing scientific research into the carcinogenic nature of cigarettes, Jackler ruled that these expert witnesses were skewing the evidence in favor of their clients, likely in exchange for money.

“By highlighting an exhaustive list of potential risk factors, such as alcohol, diesel fumes, machinery fluid, salted fish, reflux of stomach acid, mouthwash and even urban living, they created doubt in the minds of the jurors as to the role of smoking in the plaintiff’s cancer,” Jackler wrote. “Evidence shows that this testimony, which was remarkably similar across cases, was part of a defense strategy shaped by tobacco’s law firms.”

This argument is not new. Creating “reasonable doubt” in medicine has been a struggle throughout the centuries, across a spectrum of diseases. Tobacco is just the latest in a long string.

Miasma was the biggest scapegoat for diseases in the 19th century. People believed that bad smells innately caused disease, and the theory made its way into public policy. The words of Lord Edwin Chadwick, “All smell is, if it be intense, immediate acute disease.” Of course, this theory was disproven with time, but it crops up throughout history, with yellow fever (carried by the Aedes mosquito) and malaria (which means bad air in Italian, and is carried through the air by the Anopheles mosquito). It took centuries to connect these theories and many dead.

Though the smoking rates have decreased since 1965,  smoking among youths remains higher than among adults and cannot shake the destructive trend of
Though the smoking rates have decreased since 1965, smoking among youths remains higher than among adults and cannot shake the destructive trend of “young invincibility.” Original image and data from

The same goes for cancer today. Every way you turn, there is a new health book claiming some extremely common practice or good contributes to cancer and you must stop doing that now! How long will it take to cure cancer? The answer is completely up in the air. Studies emerge every day connecting some new biological function to the development cancers in different parts of the body, but all we know is that it comes from us and from the environment around us. What we can know is statistical connections, and researchers have proved again and again that tobacco consumption is linked to cancer.

Casting doubt on that by linking the plaintiffs’ cancer to other environmental factors hearkens back to the age of, “You can’t prove it’s not true.” That is fallacious thought and leads us down a road of questioning the very nature of truth, which does not serve science. Science does not deliver truth. It only delivers facts, from which we can draw truth. And the fact within the study of lung cancer is that of the patients studied over time, cigarette smoking is common. Of patients with head and neck cancers, tobacco consumption is common.

Those who listen to the arguments of these scientists without seeing the straw man of salted fish and urban living are blinding themselves. It is a strong thing, to decide that these products may be killing us, but it would not be the first time we have done it. Despite the objections of the agricultural and chemical industries, the U.S. took measures to ban DDT because of evidence that it was damaging the environment. That was a strong step on evidence accrued over 30 years, and we’ve had more than 50 to study smoking. If we can let go of the economic power that the tobacco industry wields, we may be saving lives.

And money, actually. Lung cancer patients cost the U.S. government $124.6 billion in 2010, between lost productivity and cancer treatments. It is a tenuous but commonly perceived trend that lower-income individuals smoke more than those of higher socioeconomic status. Those patients are more likely to be on Medicare or Medicaid later in life, receiving their medical care through public assistance. Cancer care is expensive; though every different type of cancer has treatments which vary in cost, it can range into thousands of dollars per month.

The point is that it’s twisted logic to allow tobacco companies, which have a known, vested interest in disassociating their product from cancer, to pick and choose their science. We may not live in a “nanny state,” and people should be allowed to make their own choices, but laws cannot be based on bad science. That is irresponsible policymaking and ill-serves the people it is meant to protect.


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