How can a top scientist be so confidently wrong? (R. A. Fisher and smoking example)

Robert Proctor points us to this lecture, “Why did Big Tobacco love (and fund) eugenicists like R.A. Fisher?” It’s pretty good! He talks about material from his 2011 book, Golden Holocaust: Origins of the Cigarette Catastrophe and the Case for Abolition, which we discussed here way back when: “If our product is harmful . . . we’ll stop making it.”

Below are some fun/horrifying slides from Proctor’s talk.

Here’s the always-charming R. A. Fisher disparaging experts by throwing around the “terrorist” label. I didn’t even know they called people terrorists that back in 1957! It looks like Fisher would fit in really well in modern academic psychology or the anti-vaccine movement:

And here’s some fun junk science (published in the Journal of the National Cancer Institute, no less!) pushing non-cigarette links to cancer:

Here’s the paper. It’s really bad! They attribute adult lung cancer to “the absence of vitamin A at birth.” It’s good to know that junk science is not a new thing. Lots of fun stuff in this paper, including the claim that, because the distribution of ages of lung cancer patients in the study is approximately normal, that “Mathematically, this means that only one factor is responsible for its origin; otherwise there would be more peaks.” Really this one deserves its own post.

Here’s a document from 1972 indicating that the cigarette company executives knew that the scientific jig was up, and it was only a matter of time before general opinion caught up with public health authorities regarding the dangers of smoking:

And here are a couple of creepy-ass dudes, one of whom was a literal Nazi and the other who has a Bacon number of 3:


Finally, a story in the National Enquirer planted by a cigarette company public relations firm:

How can a top scientist be so confidently wrong?

How did the great R. A. Fisher end up being so wrong about cigarettes and cancer? Proctor suspects that, unlike the cigarette executives (who were sitting on tons of evidence that smoking caused cancer), Fisher was not purposely spreading misinformation; rather, he was just naive. But then this just pushes the question back one step: How could this brilliant statistician be so naive?

I don’t have a full answer, but one factor may be politics. Fisher was very politically conservative, and, for whatever reason, cigarettes were a conservative cause. (On the other side were lots of far-left academics who believed in whatever far-left causes were going around.)

Beyond this, people make mistakes. Brilliance represents an upper bound on the quality of your reasoning, but there is no lower bound. The most brilliant scientist in the world can take really dumb stances. Indeed, the success that often goes with brilliance can encourage a blind stubbornness. Not always—some top scientists are admirably skeptical of their own ideas—but sometimes. And if you want to be stubborn, again, there’s no lower bound on how wrong you can be. The best driver in the world can still decide to turn the steering wheel and crash into a tree.

In the matter of smoking and cancer, Fisher comes off looking a bit worse—or maybe not so bad—as the run-of-the-mill academic hacks who cynically accepted $$$ from the cigarette companies, I guess on the theory that the money was going somewhere, so they might as well get some of it. Fisher wasn’t just taking the cash, he was also promulgating bad science.

As Proctor, Naomi Oreskes, and others have discussed, the “merchants of doubt” of the cigarette industry have used similar tactics in other scientific and policy areas, simultaneously promoting junk science while doing their best to degrade the credibility of scientific thinking more generally. I think work such as Proctor’s is valuable, even if you think he goes over the top sometimes, not just for the fun stories (but I do appreciate that) but also because it is through historical examples that we understand the world.

P.S. Interesting comment here from Paul Alper.

P.P.S. Gregory Mayer reports:

There’s a paper on this topic:

Stolley, P.D. 1991. When Genius Errs: R. A. Fisher and the Lung Cancer Controversy. American Journal of Epidemiology, Volume 133(5):416–425.

and a more recent online account;

Christopher, B. 2016. Why the Father of Modern Statistics Didn’t Believe Smoking Caused Cancer.

Both these articles are good. I particularly recommend Stolley. here are the reasons he gives for Fisher being so off on smoking and cancer:

– “Fisher sounds like a man with an axe to grind. . . . unwilling to seriously examine the data and to review all the evidence before him to try to reach a judicious conclusion.” For example, Stolley discusses Fisher’s unconventional theory of smoking and cancer and writes, “Fisher never produced any data or organized any study to follow up on this implausible hypothesis.”

– “Fisher was a smoker himself. Part of his resistance to seeing the association may have been rooted in his own fondness for smoking and his dislike of criticism of any part of his life.”

– “Fisher was upset by the public health response to the dangers of smoking not only because he felt that the supporting data were weak, but also due to his holding certain ideologic objections to mass public health campaigns.”

– “[Fisher] was good with data while working on one small set but was not easily able to integrate multiple or large data sets.” Stolley illustrates this point with a long quote from Yates and Mather, along with a detailed discussion of Fisher’s analyses of various small data sets where he picks at particular issues without looking at other relevant data or considering problems with the numbers he was looking at (for example, tables sent to him from a twin study for which no information is supplied about how the data were collected or recorded).

– “Perhaps another reason [Fisher] persisted in the cigarette controversy may have had to do with the circumstances of his life when he became engaged with the issue. He had just retired and was at loose ends. he received a lot of public attention for his views on lung cancer and fashioned a talk on the subject which he gave all over the world and which he arranged to have reprinted. It was well received, even by medical audiences.”

– “Fisher’s belief in the importance of genetics and his feeling that it is often neglected in medical research also influenced his views . . . His advancing the hypothesis as to the genetic predisposition to smoke in an effort to supplant the cigarette hypothesis reflects his intense interest in genetics.”

– “[Fisher] had wandered too far out of his field. He knew very little of the case-control method but was entirely suspicious of it because of the absence of his beloved randomization. Nor was he well informed about the ecologic data concerning smoking and cancer and, even when he comments on it, he gets it quite wrong. . . . He apparently made no attempt to put all the evidence together, to read all the older papers, to wonder if the disease was uncommon among populations that didn’t smoke. . . .”

Stolley summarizes:

There is a type of mind that is inclined to commit the fallacy of the possible proof; i.e., because an explanation is possible, it becomes somehow probable in their minds, particularly if they thought of it.

It is not surprising that Fisher and others questioned the association between smoking and lung cancer; controversy is fundamental in keeping scientific investigation from stagnating. What is startling is that someone of Fisher’s intellectual caliber would allow isolated evidence which coincided with his previously held views to blind hi to all else.

94 thoughts on “How can a top scientist be so confidently wrong? (R. A. Fisher and smoking example)

  1. It’s also the case that a lot of scientists are motivated by contrarianism (‘lots of people believe X, I’m clever than most people, so I’ll believe anti-X’). I don’t know if this also compelled Fisher to take the stance he took.

    • Kris:

      One thing I’ve seen, not quite contrarianism, is when someone sees a bad argument in favor of position X, and then uses this to conclude that not-X is true.

      Smoking’s an interesting case. There are lots of people on the anti-smoking side, and some of them do really bad work, indeed with what I consider to be an anti-scientific attitude. Seeing that bad work does not lead me to conclude that smoking, or vaping, is healthy. But I think sometimes people do reason that way.

      Daniel Davies famously wrote, “Good ideas do not need lots of lies told about them in order to gain public acceptance.” One mistake of the “I see a bad argument in favor of X, therefore I believe not-X” attitude is that it is implicitly assuming that all the arguments in favor of X are bad, or that the strongest arguments in favor of X are bad. It could well be that there are actually some very good arguments in favor of X, or that the evidence for or against X are unclear. We should point out the flaws of arguments that we see, but we have to be careful not to jump from “This particular argument in favor of X is bad” to “Not-X is true.”

      The hasty jump to “Not-X is true” is not quite contrarianism, but it does seem to have some similarities to it.

      • Obviously, I agree that “this argument for X is bad” –> “not X must be true” is poor reasoning for settling truth. However, I argue that “this argument for X is bad” –> “I believe X a bit more now” can be a perfectly rational response (and an essential tool for navigating the daily news cycle).

        I use this all the time for managing the time I spend on the confusing issue of the day: I make a reasonable effort to find primary sources that proponents of X seem to rely on the most, and I take a close look at one of these. If that source doesn’t really provide significant evidence in favor of X, then I chalk the whole thing up to meme-surfacing of a nonsense controversy.

        What should one do with claims (and evidence) from controversies that have been surfaced by non-scientific forces? I argue that you should stick with your personal prior, *and* that you should inoculate that prior from viral nonsense: “I’m still inclined to believe not-X, *and* I’m not going to allow claims surfaced from this viral controversy to temper this belief.” So not only do you not allow weak evidence to (weakly) move your prior towards X, you actually reduce your openness to claims in favor of X.

        I think this is the most rational course of action, even if it is tantamount to “this argument for X is bad” –> “I believe not-X a bit more now”.

  2. I’ve heard two rumors (I can’t remember my sources, so these are probably junk statements).

    1) Fisher was a lifelong smoker who really enjoyed smoking pipes, and hence had a strong personal bias.

    2) Fisher took money from Big Tobacco (R.J. Reynolds).

    Of course, at this point any discussion of Fisher’s motives is pure speculation. But historical figures are more complex than we think.

    • I’ve heard 1) many times, and based on the Fisher-pipe photos it seems likely. Given 1) this becomes not “how could a top scientist be so confidently wrong” but “here’s an example of personal bias”.

      Also, I’d say that some of the early skeptical takes on the smoking cancer link weren’t really so confident. Fisher asked for more data “a good prima facie case had been made for further investigation…Is not the matter serious enough to require more serious treatment” (BMJ 1957)

      Whether you believe his arguments were bought by the tobaccos industry to influenced by his bias he’s saying he believes there is a good case for the link (and states that he believed this in 1952, for reference the famous British doctor’s study started in 1951) but that it hasn’t been conclusively shown, and at this point even Hill and Doll would have agree, hence why they did the British doctor’s study. He was arguing a point not so dissimilar from that seen on this blog, that correlation doesn’t imply causation. The fact that he was wrong doesn’t mean the skepticism of the initial studies was misguided. Remember that smoking was for some time believed to be beneficial, then a set of studies comes out showing a very unexpected and large negative effect of smoking. Should he have taken the large, counterintuitive (and provocative) result from a study with some methodological issues (arguments were that the control group for the initial study may not have been matched on some unknown important covariates) at face value? Hindsight of 70 years is almost perfect, we know smoking causes cancer in 1952 they didn’t, but if these were genuine concerns (and not bought which I don’t know if they were) then is this really so different from the skepticism expressed on this blog for some studies?

      Personally, I’ve never been very scandalized by this part of Fisher’s life; there are plenty other more distasteful things in his life than this.

        • I’d never heard that heard before but I don’t doubt it based on accounts of his personality; this is certainly not the only quote or known instance of him being a jerk. Again, this gets back to the question of “how was he so wrong?”. Was it his temperament, his personal bias, his pride, money, or a scientific error? The arguments he published that I’ve seen aren’t so outlandish, even if now known to be wrong so I’d imagine it was a mix of the first 4. Which means even great scientists have the same failings as everyone else.

        • From what I’ve read about R. A. Fisher, if he felt someone was challenging his views/scientific opinion, he went on the extreme attack. Perhaps that is what happened at the AAAS Meeting. Someone asked him a challenging question and then used that phrase.

          Oscar Kemthorne had good advice regarding great scientists and used Fisher as an example. Dr. Kempthorne said that one should always critically examine arguments made by great scientists; they could be wrong. The standing of thescientist vs a vis the person examining shouldn’t matter.

        • Dr. Kempthorne said that one should always critically examine arguments made by great scientists; they could be wrong. The standing of thescientist vs a vis the person examining shouldn’t matter.

          Well, yes. The original motto of science was nullius in verba. But it is also incorrect to take Dr. Kempthorne (no idea who he is, but does not matter) as an authority too.

          Maybe “incorrect” is the wrong term. Relying on argument from authority/consensus heuristics can be useful, but you need to be very careful.

  3. You keep asking “how was Fisher so wrong?”, but don’t provide us with either the evidence he had access to nor the evidence that has convinced you.

    Tobacco smoke is actually a very weak carcinogen. No animal model existed until long after Fisher’s death, and what they had to do is very extreme. Basically upon birth the mouse is immediately exposed to smoke all day, every day until they are an adult. But this is still not enough, then the smoke exposure must be stopped. It is only when the lungs begin to heal that the tumors form.

    Strain A mice were exposed first to a comparatively high concentration of ETS, generated from the sidestream (89%) and mainstream (11%) smoke from burning Kentucky 1R4F cigarettes, as described before in detail [9]. After a 5-month exposure, the animals were allowed to recover in air for another 4 months before evaluation of the lung tumor response. The same protocol was eventually adopted by three other laboratories [10–12].
            […]
    The flat dose-response suggests that tobacco smoke is a comparatively weak carcinogen. A previous study in which a dose-response was conducted in one single experiment came to the same conclusion [13]. It may to some extent explain why most inhalation studies done with tobacco smoke in mice failed to give a positive tumor response [14, 15]. The fact that ‘‘only’’ 10% to 25% of all smokers develop lung cancer [16] might also be construed to indicate that tobacco smoke is not a very potent carcinogen in man.

    https://www.ncbi.nlm.nih.gov/pubmed/15765916

    Think about it. How many substances can you breath in high doses of nearly all day, every day, for decades and still have only 10% chance of lung cancer.

    Then there are the tuberculosis (it is easy to misdiagnose one as the other, especially without testing/imaging that did not exist in Fisher’s time) and nuclear testing (unlike tobacco smoke , it is easy to give mice lung cancer with radioactive dust) confounds in the observational data.

    • What the hell are you talking about? Nobody cares about how strong of a carcinogen tobacco smoke is relative to radioactive dust. The issue is whether or not people should be warned against intentionally inhaling it in large doses every day.

      • No, the question is “How was Fisher so wrong?”

        The answer is that the evidence for smoking causing cancer is actually pretty weak. You just think it is strong because you’ve never really looked into the topic and have heard it repeated so many times.

        And it was much weaker in Fisher’s time.

        @Andrew

        You still haven’t shared what evidence you think Fisher missed.

        • Anon:

          You should get up to date on cigarette company propaganda. For quite awhile the party line has been that cigarettes cause cancer, and that everyone has known this fact for many decades. See for example here. If you want to take a more strongly denialist position than the Philip Morris and the Surgeon General, go for it. From here it looks like you’re playing politics or what Tyler Cowen calls “mood affiliation.”

        • How is asking for the evidence that you think should have convinced Fisher in the 1950s “denialist”?

          Also, what does that have to do with me being up to date?

          Please do not actually answer those questions though, because those topics distract from the original one:

          What is the evidence you think Fisher missed?

        • No, the question is “How was Fisher so wrong?”

          Fisher’s claim was that the people who were warning people about smoking were wrong to do so. My point isn’t that tobacco causing cancer is obviously true or that it was in the 1950s, my point is that you’re throwing out all kinds of completely irrelevant information, like the relative carcinogenic strength of tobacco smoke to radioactive dust.

        • Somebody: Yup.

          Anon:

          1. Proctor discusses evidence as of 1957, some of which was known to the cigarette executives but not to the general public. The point is not that Fisher should’ve been sure that smoking caused cancer; the point is that his theories were outlandish even at the time. There’s nothing wrong with proposing outlandish theories—that’s part of science—but it was ridiculous for Fisher to be so confident in his wacky theories, hence the title of my post.

          2. The “denialist” part of your comment was not asking for evidence fro 1957, it was your statement that “the evidence for smoking causing cancer is actually pretty weak,” a claim that’s denialist enough that it goes beyond the position on smoking and cancer that Philip Morris has held for decades.

          It’s somewhat interesting to have this discussion, not because of the smoking, but to see this example of mood affiliation and the politicization of science. But I guess we’ve gone around this enough; as Phil would say, the discussion is now in “garbage time.”

        • If you had provided the evidence, we would be discussing that and the conversation wouldn’t have gone off track.

          But yes, even the evidence today amounts to some very artificial experimental conditions (that seem to show quitting smoking after a lifetime of it can be dangerous) and a bunch of highly confounded observational studies.

          This is weak evidence that would never stand up to scrutiny like the cold fusion claims got from fellow physicists. It is towards the top for medical research though.

          Btw, I do think smoking damages the lungs, which causes cancer.

          According to the current belief, anything that leads to increased proliferation causes cancer. You only get so many divisions in a tissue before either the wrong set of mutations accumulate or there is organ failure.

        • @Wonks

          I didn’t watch the video (yet), but I don’t see anything in the post where Fisher said smoking *does not* cause cancer.

          Referring to people who claimed it did based on whatever limited evidence was around (which I would still like to see) “terrorists” means he thought *they* were overconfident.

    • Anon:

      Your response is consistent with what Proctor hypothesized, which is that Fisher was a naif rather than a purposeful killer, and that, unlike the tobacco company executives, he wasn’t aware of the up-to-date research showing that smoking caused cancer. The question remains, though, why Fisher was so obnoxiously sure of himself, to the extent of labeling anti-smoking efforts as terrorism. “Radioactive dust,” indeed!

    • I read the title of the post, the content of the OP, and then scrolled through the comments, wondering how long until Anony00d/”NonBel” (as he’s known on Ycombinator) would crud up the discussion, and wasn’t very surprised to see it had already happened. This type of post is like a Bat-Signal for this sad, deranged, reasoning-deficient character. His knowledge of smoking and cancer-related risk is just so fundamentally poor, and expects message board readers to have time to educate him, or “point him to the evidence” (which he would dismiss or misunderstand). We’re not public utilities, however.

      This blog was so much better when he got asked to leave for a few weeks. As Shaw famously wrote: “Never wrestle with pigs. You both get dirty and the pig likes it.”

        • “Yeah I sincerely wish there is a way to block or ignore people on this.”

          Well… I don’t know about blocking… but ignoring someone is within each person’s power.

        • Ignoring is not so easy, at least for me! It takes conscious effort for me to NOT read specific comments, and if I read them I sometimes get so incensed that it’s hard to resist responding. I’m not the only one; this is why ‘trolling’ works.

          That said, I hope Anoneuoid doesn’t get banned just for posting stupid, irritating, or trolly stuff every now and then. Sometimes he says something thought-provoking, or says something true that I didn’t know about previously.

          In this case, I think it’s a fair point that we have to be careful to judge Fisher based on what was known at the time, not based on what we know now, and also fair to suggest that we should be sure we know what we’re criticizing Fisher for. When he used the word “terrorists” was he referring to people who said they _thought_ smoking caused lung cancer, or to people who said smoking _definitely_ causes lung cancer, or to people who said smoking would give _all_ smokers lung cancer, or what, exactly? (Personally I wouldn’t compare any of these groups to terrorists, but I still think the question is relevant to how I judge Fisher, and thus is relevant to what lessons I can learn for myself if I think of Fisher’s story as this cautionary tale).

          That said, the idea that it’s up to ‘us’ to come up with ‘the evidence that Fisher missed’ is just such incredibly irritating. By the early 1950s there was good evidence that smoking caused or promoted lung cancer and heart disease. The evidence wasn’t perfectly ironclad and it was still possible to make the correlation-not-causation argument, but it seems that Fisher was not simply unconvinced, he was _sure_ that smoking did not cause lung cancer. ‘What evidence did Fisher miss,’ I dunno, perhaps he didn’t miss any evidence at all. He certainly knew about some of the studies and some of the evidence and he was sure it was all hooey. The question ‘what evidence did Fisher miss’ completely misses the point that he had such a strong prior belief that he was unwilling to accept that cigarettes might indeed be dangerous. Indeed, if he didn’t miss any evidence, but still dismissed the idea of a causal link, then that’s more of a reason to criticize his failings, not less.

          And finally: For those interested in the progression of the medical understanding of smoking risk, there’s a short history at https://www.cancer.org/latest-news/the-study-that-helped-spur-the-us-stop-smoking-movement.html

          I’m sure there are better sources, of course, but this was what I found in 30 seconds of searching and who has time for more?

        • > it seems that Fisher was not simply unconvinced, he was _sure_ that smoking did not cause lung cancer

          Was he? From the third link in Thanatos Savehn’s interesting comment below:

          Sir Ronald Fisher has stated “of course, tobacco may cause lung cancer. I am only concerned to try and assess the evidence”.

        • Carlos,
          OK, you’re right, he wasn’t _sure_ smoking didn’t cause lung cancer (and other maladies), or at least he never said so. But he did _act_ as though he was sure it didn’t cause lung cancer etc. He was incensed because the medical establishment was engaged in “the organized creation of states of frantic alarm” and it seems — based on my admittedly very limited reading — that he would come up with any hypothesis, no matter how nutty, rather than admit that there was indeed a lot of evidence that smoking causes lung cancer. (Maybe people take up smoking because they have early lung cancer, which irritates their lungs, so they take up smoking to soothe them. Maybe people who are genetically predisposed to lung cancer are also genetically predisposed to smoking. And so on).

          If Fisher thought there was even a 10% chance that smoking was causing tens of thousands of lung cancer deaths per year, it’s hard for me to imagine he would be so vociferous in his attacks on anti-smoking campaigns. But perhaps I’m wrong.

  4. At about the 23 minute mark of Proctor’s talk, he mentions Fisher’s lecture at the University of Wisconsin in February, 1960. I was there and, as it happens, coincidentally wrote about this experience a few months ago for a British online journal. In essence, I attended the lecture out of ignorance–I had never even heard of mean, median, mode, standard deviation–and convenience because February tends to be cold in Wisconsin and the room was reliably heated. Here is a salient bit of what I wrote:

    “Fisher was speaking on the hot topic of that day: was smoking a cause of cancer? Younger readers may wonder how in the world was this a debatable subject when in hindsight, it is so strikingly obvious.”

    I concluded with:

    “I was in my mid-twenties and I doubt that there were many people younger than I was at that Fisher presentation, so I am on track to be the last one alive who heard that lecture by Fisher disputing smoking as a cause of cancer.”

    And, I have no idea of whether or not I have already succeeded.

  5. This is almost completely unrelated, but I’m taking the opportunity because Proctor’s name has come up. I strongly recommend his early book “The Nazi War on Cancer”. I used it in teaching a few times in order to counteract the tendency of my enviro students to believe that being green is always pure and virtuous, and that progressive stances wrt the environment “naturally” converge with those on equality, justice, democracy, etc. The final chapter is especially strong, since it connects with modern US environmentalism.

    Just to be clear, I am a progressive/green person myself, but I hope I avoid lazy assumptions and “good begets good” heuristics.

    • RE “The Nazi War on Cancer”

      Here’s on the current modern official “War on Cancer” operation…

      Most people would be much smarter and better informed if they had awareness of what the “war on cancer” movement (and the “Breast Cancer Awareness” movement) do NOT raise awareness about.

      Knowing that the most prominent cancer charities (Komen, American Cancer Society, etc) are large self-serving businesses instead of “charities” or that these groups suppress critical information on cancer, such as the known causes of cancer (instead they talk about “risk factors” of cancer) or that many “breast cancer survivors” are victims of harm instead of receivers of benefit, or that they’ve been intentionally misleading the ignorant public with deceptive cancer survival statistics, or that government health bodies such as the NIH are merely a pawns for corporate medicine, etc is a good start to get to the real truth (read this well referenced scholarly article’s afterword on the war on cancer: do a search engine query for “A Mammogram Letter The British Medical Journal Censored” by Rolf Hefti, and scroll down to the afterword that addresses the ‘war on cancer’).

      The recognition that breast cancer awareness was started by these business interests is another piece of the real awareness about the pink ribbon cult and the traditional war on cancer. Or that the orthodox cancer business has been denouncing, suppressing and squashing a number of very effective and beneficial alternative cancer approaches (instead they sold you the lie that only their highly profitable/expensive, toxic conventional cancer treatments are relevant). You probably guessed why: effective, safe, inexpensive cancer therapies are cutting into the astronomical profits of the medical mafia’s lucrative treatments. That longstanding decadent activity is part of the fraud of the war on cancer.

      So, raising “awareness” about breast cancer or raising funds for the war on cancer have hardly any other function than to drive more unsuspecting people into getting more expensive and unnecessary tests (think mammography) and then, often, cancer treatments (chemo and radiation therapy).

      The reality is that the war on cancer has been and still is, by and large, a complete failure (read Dr. Guy Faguet’s ‘War on cancer,” Dr. Sam Epstein’s work, or Clifton Leaf’s book, or Siefried’s work on this bogus ‘war’). The criminal medical establishment deliberate and falsely self-servingly claims and distorts a ‘win’ in the bogus ‘war on cancer’ when the only notably win is a reduction in lung cancer due to a huge reduction in smoking, which has nothing to do with their cancer treatments. Lying is their mode of operation.

      Since the war on cancer began orthodox medicine hasn’t progressed in their basic highly profitable therapies: it still uses primarily and almost exclusively highly toxic, deadly things like radiation, chemo, surgery, and drugs that have killed millions of people instead of the disease.

      As long as the official “war on cancer” is a HUGE BUSINESS based on expensive TREATMENTS (INTERVENTIONS) of a disease instead of its PREVENTION, logically, they will never find a cure for cancer. The upcoming moonshot-war on cancer inventions, too, will include industry-profitable gene therapies of cancer treatment that are right in line with the erroneous working model of mechanistic reductionism of allopathic medicine. The lucrative game of the medical business is to endlessly “look for” a cure but not “find” a cure. Practically all resources in the phony ‘war on cancer’ are poured into treating cancer but almost none in the prevention of the disease. It’s proof positive that big money and a total lack of ethics rule the official medical establishment.

      It’s just like with any bogus official “war” (‘war on drugs’, ‘war on terrorism’, ‘war on covid’, etc) — it’s not about winning these wars but to primarily prolong them because behind any of these fraudulent “war” rackets of the criminal establishment is a Big Business, such as the massive cancer industry. The very profitable TREATMENT focus of conventional medicine, instead of a PREVENTION focus which these official medical quacks (or rather crooks) can hardly make any money off, is a major reason why today 1 of 2 men and 1 in 3 women can expect a cancer diagnosis at some point in their lifetimes yet that rate was multiple times lower 5 decades ago when the phony ‘war on cancer’ began (1 in about 16). And 5 decades ago when this bogus war began cancer was the second leading cause of death and 50 years later it is STILL the second leading cause of death in the country this “war” was declared in. These facts alone prove we are NOT winning the war on cancer.

      The history of the pink ribbon movement and the alleged war on cancer is fraught by corruption, propaganda, and the hoodwinking of the unsuspecting public. The entire war on cancer is a disinformation campaign. The real war is on the unsuspecting public. Does anyone really think it’s a coincidence that double Nobel laureate Linus Pauling called the ‘war on cancer’ a fraud? If you look closer you’ll come to the same conclusion. But…politics and self-serving interests of the conventional medical cartel, and their allied corporate media (the mainstream fake news media), keep the real truth far away from the public at large. Or people’s own denial or indifference of the real truth.

  6. Perfection: “Brilliance represents an upper bound on the quality of your reasoning, but there is no lower bound.” A poster with this caption would be stocked in every university book shop if Einstein had said this! Someone might need to make an inspirational Gelman poster soon. :)

        • This one I think we should be careful with. If the data you have doesn’t really measure the right things, or is so poorly measured that it can’t be relied on, then better not to “go to war” at all. Otherwise it is too easy an excuse for all sorts of bad behavior. But you point is well taken in that lack of perfect data should not be used as a reason to not do the analysis.

  7. > It’s good to know that junk science is not a new thing….

    Shouldn’t that be the default assumption?

    This touches on a pet peeve – the oft’ heard refrain about a “crisis” in science. To me, a “crisis” implies a crescendo, a trend over time, that presents an impending danger – not just basically the status quo. Sure, “science” has its issues. But where are the robust studies that show (1) the % of science that is “junk” has grown or (2) the net effect of more junk science, because there’s more junk science overall not because the % of science that is junk has grown, leads to a differentially worse state?

    Here’s my guess: the net effect of “science” has grown as a benefit to society over time. Hard to measure, of course, but that’s my guess. So even if the proportion of science that is junk has grown (I’m skeptical about that) it’s still small enough that the growth in “science” overall more than balances out the greater impact of junk science than in the past (because the net effect of growth in beneficial science dominates – because it is a larger proportion of science overall).

    I have no idea whether anyone can decipher that or cares enough to try – but I would appreciate feedback.

    • I wrote this just after listening to a podcast with Thomas Piketty, where he discusses the importance of viewing his scholarship about the diliterious impact of inequality within the long-term context of dramatically increased equality across the world.

  8. I get worried when 100% of experts agree on something. Either the evidence is overwhelming, or the contrary view is being suppressed somehow.

    Today, smoking does not just cause lung cancer. Smokers are said to be put at risk for dozens of illnesses. No one is willing to admit that anyone gets any benefits from smoking.

    I hate smoking myself, but it seems obvious to me that smokers are getting some benefit, just as drinking beer and taking drugs have benefits. The harms may be overstated, and the benefits may be worth it for some people.

    • I agree with this entirely (and am also a lifelong nonsmoker.)

      I once read (true? false? anyone?) that the probabilitiy of a lifelong heavy smoker getting lung cancer was about 25%. (Of course, it’s well under 5 percent for nonsmokers…) When I first heard it I found the number shockingly low… when you add in emphysema and other COPD problems the number rises, but much less than I thought it would. (Heart disease is another matter, since the fraction of heart disease actually caused by smoking is decidedly unclear, and heart disease is such an overall gigantic killer.) At that point, it seems like the next step is cost-benefit analysis, not near-fanatic levels of discouragement.

      • If you believe that 2nd hand smoke causes (non-consentual) harm to others (many contrarian don’t), then don’t forget to include that outcome as you balance costs and benefits to understand “near fanatic”* levels of discouragement. And of course, years of life lost, the economic costs of addiction, etc.

        *(How do you draw lines between not so fanatical and near fanatical and actually fanatical discouragement? What are your metrics?)

        • Yeah, but the second-hand smoke numbers are dramatically weaker… orders of magnitude weaker… if not all the way to junk science weaker.

          You ask a fair question about where I draw the line on fanaticism, and I punt: I just know it when i see it. I mean… it could have been worse — cigarette sales could have been banned altogether. (That would cause me to remove the “near”)

        • BTW, the banning of menthol as an additive is one step on the fanaticism scale. As are the restrictions on vaping (as Andrew mention in the OP)

        • > I mean… it could have been worse — cigarette sales could have been banned altogether.

          Seems kind of a tautology. By what metric would banning sales have been worse?

        • By the metric that those who understand the risks and whose benefits outweight he costs would still be allowed access without breaking the law.

        • I still don’t understand.

          What are the costs as you define them?

          Seems to me you are embedding some kind of metric for evaluating cost. I’m asking what it is.

          When I started smoking (maybe about 14? or so) I didn’t exactly sit down and calculate the risks against the costs before I started. When I still smoked, as an addict I would rationalize it to myself in real time all the time and fire one up, even though when I thought it through more I felt strongly that the costs way outweighed the benefits.

          I think this is complicated. But you seem to have some clear calculus in operation.

        • The costs of the fanaticism, I mean.

          The costs of the addiction seem clearer to me; although quantifying them is somewhat complicated the metrics seem pretty obvious.

      • I’m too lazy to look up the stats but I’d be very surprised if the lifetime risk of a heavy smoker dying of lung cancer is as high as 25%. I think it’s maybe half that.

        The main smoking risk (to mortality) is heart disease, not lung cancer risk.

    • I have been working in a tobacco-related position recently, and I want to make some points in response to this line of argument. I apologize, this is a little scattered.

      To start, if you look at actual tobacco science or even detailed tobacco journalism like The Devil’s Playbook, rather than advocacy material, you will not find it that hard to find an acknowledgment that tobacco at least initially has benefits for focus and alertness among possibly other “beneficial” or enjoyable stimulant effects. The problems are several, though: first, like virtually all addictive drugs, many users fairly quickly develop a tolerance, and once this has occurred, doses similar in size to the initial dose simply get you back to about what your baseline was before you ever tried it, unless you start chasing the dragon with larger and larger doses. Moreover, if you are one of the many people who experiences tobacco this way, your chemical baseline when you don’t have nicotine in your system is lower than it was before you started using it.

      Second, there are good reasons the public health messaging on tobacco lacks nuance. Studies have long found that (at least in US contexts) you have to beat young people over the head with the negatives to have any prayer of affecting their propensity to smoke, and if you offer too much nuance or accidentally make smoking look at all cool, your attempts to reduce smoking can actually be counterproductive. For the most part, neither tobacco marketing nor marketing-based anti-smoking campaigns are really targeting anyone older than about 25, because if you haven’t tried it by 25 your propensity to ever get hooked is very very low.

      Also, the tobacco companies and their consultants have acted in bad faith again and again and again and in my observation, public health people who work on tobacco have pretty much decided that they’re willing to do without some valid critiques from those researchers if it means not wasting a lot of time on people whose entire job is to sow doubt. Is this an overreaction? Maybe, but I understand why the community has moved this way.

      Last, there is a huge divide in public health research on tobacco between the harm reduction people and the endgame/elimination people; the field is almost at war with itself at times in recent years. You will generally get more nuanced takes out of the harm reduction people but I do think the endgame people have a point.

      • very well put. i know this blog attracts skeptics, but even so, the pro-smoking takes are surprising.

        in books introducing sensitivity analysis, the go-to example for “observational study completely insensitive to plausible confounders” is smoking and lung cancer…making “clever” arguments to refute or minimize that link is much closer to postmodernism than to skepticism.

      • Anon:

        Regarding your point about addiction, I’m reminded of a conversation I had once with two statisticians, one who worked for the cigarette companies (call him C) and one who worked for a drug company (call him D):

        Statistician C: “Everybody talks about how nicotine is ‘addictive.'” What about skiing? Skiing’s more dangerous than smoking. Why don’t they talk about making skiing illegal?”

        Statistician D: “I’ve never heard someone say they want to quit skiing but they can’t.”

        D’s argument seemed convincing to me. It seemed to me that C was contorting himself and making ridiculous arguments in order to let the cigarette companies off the hook. In some sense, that made sense, as this was his job, it was what they were paying him to do, but it still annoyed me that he was making those arguments to me, even in an after-hours event when he wasn’t on the clock and had no duty to parrot the company line. I guess he’d contorted himself to the point that he really believed what he was saying. And that was upsetting to me on a different level.

        • Sports addiction is also a thing. (As addiction to anything can be a thing nowadays, maybe – the point is that there are people who discuss the subject seriously.)

      • Second, there are good reasons the public health messaging on tobacco lacks nuance. Studies have long found that (at least in US contexts) you have to beat young people over the head with the negatives to have any prayer of affecting their propensity to smoke, and if you offer too much nuance or accidentally make smoking look at all cool, your attempts to reduce smoking can actually be counterproductive.

        Not to side with the contrarians here — I think the public health campaign against smoking in the United States has been a massive utilitarian success. But nonetheless, I disagree hard with this line of reasoning. First of all, as a matter of principle, I think representing things honestly is just right. Furthermore, as a recently young person, when you don’t represent things honestly, people start to distrust you altogether. I remember believing that illicit drugs were plutonium dangerous substances handled only by the most antisocial 1% of society. When we hit college and realized virtually everyone had at least tried weed and half our teachers smoked it regularly and half the respectable wall street bankers were using coke, it led to a lot of misinformed “just try anything” experimentation. The disinformation also provides tons of cover for disastrous carceral policies.

        Also, “accidentally make smoking look at all cool”? Come on! Let’s be honest; smoking is cool. Looking calm but disillusioned, lighting something on fire, taking a big whiff and blowing the smoke out of your mouth–it’s almost the definition of cool. The only way to not make it look cool is to not show it at all.

        • somebody –

          > Furthermore, as a recently young person, when you don’t represent things honestly, people start to distrust you altogether

          Not to defend deception but…

          I see the logic in pointing to that dynamic but I think it should be grounded in the full context against (1) the potential PR benefit of the deception – (which is larger, the negative or positive effect or what is the ratio?) and, (2) the effect of the deception decreasing trust relative to other factors, like just general tribalistic motivated reasoning or the ubiquitous campaigning by binary-thinking contrarians pushing an anti-“expert” agednda.

          I point to that last aspect because the refrain that “activists have driven a loss in trust in science” in the domain of change domain is often made but seldom supported with evidence about the (net effect of) theorized causality and assumptions about the existence and magnitude of a loss in trust itself is easy to speculate about but kinda are to really quantify.

      • In terms of the public health messaging, I heard the British comedian David Mitchell make an interesting suggestion. He said that pushing the message of smoking being deadly is bad strategy. The danger is largely in the far future and doing dangerous things is cool when you’re young anyway. His alternative was to focus on the way smoking affects features like smell and perceived hygiene. The social castigation dangers that come with being considered smelly are immediate for teenagers and, unless I’m even more out of touch than I know, being smelly is not cool.

    • Roger,
      You can say the same about anything addictive, but if you talk to former addicts, they will tell you it wasn’t worth it. I smoked when I was young, long ago, and I can tell you it wasn’t worth it.

      On the main point of this thread, my physician father, also a smoker, knew enough just about statistics to take comfort from Fisher.

    • I think there’s an argument that smoking helps with schizophrenia symptoms, which is why so many individuals with schizophrenia smoke. No conclusive research on it to my knowledge. Nor, to my knowledge, is this argument being suppressed.

  9. “Brilliance represents an upper bound on the quality of your reasoning, but there is no lower bound.”

    This is pure gold. Did you (or someone else) use it somewhere before or should I cite this post when I use it?

  10. A quick look at Wikipedia turns up:

    “Robert Neel Proctor (born 1954) is an American historian of science and Professor of the History of Science at Stanford University, where he is also Professor by courtesy of Pulmonary Medicine.”

    Stanford gets hammered so often in this blog so Proctor’s association is surprising. And, what in the world is meant by the phrase, “Professor by courtesy of Pulmonary Medicine”? Does this designation exist only at Stanford’s Pulmonary Medicine? Elsewhere in some form at Stanford? Totally absent at Harvard, Yale, Princeton, Columbia, etc.?

  11. There’s a paper on this topic:

    Stolley, P.D. 1991. When Genius Errs: R. A. Fisher and the Lung Cancer Controversy. American Journal of Epidemiology, Volume 133(5):416–425. https://doi.org/10.1093/oxfordjournals.aje.a115904

    and a more recent online account;

    Christopher, B. 2016. Why the Father of Modern Statistics Didn’t Believe Smoking Caused Cancer. Priceonomics https://priceonomics.com/why-the-father-of-modern-statistics-didnt-believe/

    Stolley was an epidemiologist; Christopher seems to be a journalist. (I only skimmed Proctor’s captions; perhaps he cited these as well.)

  12. Maybe Fisher wasn’t that brilliant. Perhaps he was just your typical better-than-average researcher who was at the right place at the right time.

    At a key moment in his life, and in the history of statistics, he set about firming up the foundations of statistics and did an epically bad job of it. I’m not sure why people are surprised when Fisher, (and Neyman) weren’t very good at analyzing observational data.

    • Anon:

      It’s my impression that Fisher made some major mathematical and conceptual contributions from 1910 through 1930 or so. By the late 1950s, not so much. Also, for better or worse, statistics was not an academic field back then in the way it is now, hence it makes sense to that Fisher (and Neyman) could have been brilliant in some subfields of statistics but clueless in others. And, in both cases, not having a clear enough picture of statistics to have a sense of the boundaries of their expertise.

      • I suppose his design of experiments. Most of his other stuff was manipulating Gaussian integrals, which while handy, doesn’t inspire awe. At least he was a practicing scientist though. Neyman paper’s read like the work of a deeply unimaginative mathematician who only heard about science from gossip.

        I don’t get why so many are impressed by them. They lived at at time when anyone with the desire could rack up statistics papers. And the science train they derailed still hasn’t been put back on the tracks.

        I truly don’t get what anyone was expecting with their analysis of observational data. Some deep perceptiveness that mere mortals couldn’t duplicate?

        It’s worth remembering that every field has “top” people. Even if the field failed. Even if the field didn’t use the opportunities it had. Even if their work lead to disasters. There will still be people in that field hailed as “geniuses”.

        On a related note:

        In the 30’s Einstein submitted a paper to physics journal, who’s editor had it reviewed and found a major mistake. Einstein was indignant that one of his papers should be treated that way. He later quietly corrected the mistake and had it published.

        Fisher, who was the field of Geophysics for a long time, not only fought the theory of continental drift, but in an edition of his major work published in the late 70’s, still slammed the theory long after everyone had accepted it.

        • Anon:

          Five of Fisher’s major contributions were in the areas of logistic modeling, maximum likelihood, factorial design, the analysis of variance, and genetics. Each of these alone would’ve been a big deal. I agree that the math in this work, considered as math, is not earthshaking. Considered as applied math, though, it’s all really good stuff. But this didn’t stop him from getting confused on issues such as causal inference and hypothesis testing. That’s just the way it is. The sad thing is not that Fisher was not an expert in all areas of statistics; it’s that he didn’t recognize the limits of his expertise.

        • @Andrew

          Do you have an example of Fisher getting confused? I have seen both Pearsons, Neyman, and Student (Gosset) do it but never could find an example of Fisher misinterpreting the result of one of his significance tests. And I tried to find one a few years ago.

        • Anon:

          I don’t know the history of this, but I know that Rubin talks about the “Fisher null hypothesis” as being the hypothesis that the treatment has zero effect on all units, and then there are confidence intervals constructed by inverting a series of hypotheses where the treatment has a constant effect. I don’t think that makes sense. Unrelatedly, Rubin also had an example where Fisher mistakenly adjusted for an intermediate outcome, thus getting the wrong answer for a causal inference problem. As Rubin said, statistical inference is confusing, and researchers back then didn’t have good notation, which led them to make mistakes that we might be able to avoid today.

        • H_0: if Fisher, Neyman, and E. Pearson had of done their job right, there would be no reproducibility crises today.

        • I’m not being snarky. I really tried to find Fisher misinterpreting rejection of one hypothesis as evidence for some other hypothesis and couldn’t find an example.

          If it exists I would like to see it.

    • Well, perhaps the word genius is overused but I do think Fisher was a genius. I like L. J. Savage’s article “On Rereading R. A. Fisher”, Annals of Statistics, 1976, 5, 441-450 for a balanced discussion of his contributions and his faults.

      In Joan Fisher Box’s collected letter of Fisher, there is an interesting correspondence between Fisher and a leading combinatorialist of the day. The mathematician posed an usolved problem to Fisher regarding Latin Squares. He had read that Fisher was an expert in using them. Fisher wrote back an intuitive answer to the question. The mathematician wrote that he had solved a problem that he had struggled with for 30 years.

  13. The discussion about tobacco smoke being “weakly carcinogenic” — in that it takes years of frequent exposure to produce a significantly elevated probability of lung cancer — raises a question: what other things have a similar harm profile, but don’t get the same press nor moral opprobrium?

    Obesity (overeating) might be one. Eating too much at one meal, or even over an entire holiday week, does very little harm. Constantly overeating, so that you remain obese over a very long period of time, does create significant dangers to your health. But in contrast to smoking, there’s a social taboo to mentioning this — I’ve heard of doctors holding back from telling their patients to lose weight for fear of being accused of “fat shaming.”

    Getting insufficient sleep is another possibility. Chronic sleep deprivation is known to have lots of detrimental effects on one’s health, but again, only if it’s chronic.

    I don’t know if my two examples actually cause comparable harm to smoking, but if anyone reading this knows, please chime in.

    • Kevin,

      Regarding the doctors and obesity thing: that’s an interesting question, what advice are doctors giving to their patients? A quick google of *surveys of doctors advice to patients obesity* yields some interesting information:

      An article from 2009 reporting a survey of 101 physicians who “rated the extent to which they recommended various weight control strategies to their obese patients.” The findings: “The most common strategies recommended were increasing physical activity, reducing consumption of fast foods, reducing portion sizes, and reducing soda consumption. . . . Physicians reported that, from their perspective, the equivalent of a 21.5% weight loss would be an ‘acceptable’ outcome for a hypothetical obese patient; a 10.6% weight loss ‘disappointing.'”

      A similar paper from 2012 reporting on a survey of 500 physicians.

      A survey from 2013 of 1000 members of the general adult population and 500 physicians, finding “that only 56 percent of overweight or obese adults report ever having discussed weight with their doctor, yet all physicians surveyed say they counsel their overweight and obese patients about diet and exercise. Less than four in 10 of those adults said they have been told to lose weight.”

      So I’m not sure what to think. These surveys don’t seem to report doctors holding back from telling their patients to lose weight, but it’s hard to know what to make of a result such as, “Nearly all physicians (92 percent) say they discuss Body Mass Index (BMI) with their overweight/obese patients, yet two out of three adults (67 percent) who have discussed weight with their physician say BMI was rarely or never part of that discussion”

        • “it’s taboo, at most, in certain Extremely Online corners”

          I dunno. Nature has had several articles this discussing how “sizeism” is a big problem in science and how science needs to accommodate obese people. I don’t think it’s okay to fat shame anyone, but the “body positivity” movement is alive and well and it would be taboo to say someone needs to lose weight in many facets of mainstream life.

      • > Nearly all physicians (92 percent) say they discuss Body Mass Index (BMI) with their overweight/obese patients, yet two out of three adults (67 percent) who have discussed weight with their physician say BMI was rarely or never part of that discussion

        I imagine it’s because BMI isn’t a terribly useful or intuitive statistic.A physician might use it to say “you’re overweight”, but a patient isn’t going to remember that their number is 29.4 or something.

      • ‘ it’s hard to know what to make of a result such as, “Nearly all physicians (92 percent) say they discuss Body Mass Index (BMI) with their overweight/obese patients, yet two out of three adults (67 percent) who have discussed weight with their physician say BMI was rarely or never part of that discussion” ‘

        It’s hard to figure that out? :) Hat tip to the utility of surveys! :) It’s pretty safe to conclude that some unknown proportion of ppl don’t provide the correct information on what actually happened or what the actually think or what they would actually do when responding to surveys. In this case there is an obvious motivation for both patients and physicians to selectively remember or whatever other term you want. But OTOH guessing people’s motivation is hard since you don’t know what it is, and that’s aside from the infinite possibilities that can’t be constrained.

    • Actually, smoking (probably nicotine) spikes your blood sugar. This is why people usually gain weight when they quit.

      Looks like it works out to 5-10 lbs on average, with 10-20% gaining at least 20 lbs: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5004778/

      I’ve wondered if that aspect partially counteracts the lung damage. Imo, the carcinogenicity of tobacco smoke to is surprisingly low. I’d guess there is likely something protective about it. This would never be studied or acknowledged in the current environment of course.

      • Anon:

        Enough! This is getting ridiculous, and I agree with the the other commenters that this is just wasting everyone’s time. Please take it to twitter, where you can get all the attention you want for these contrarian takes.

    • The one that’s drawn parallels in recent years is cured/processed meat (IE those containing nitrates) such as hot dogs, bacon, and deli meat and their effect on bowel cancer (hence the rise of ‘uncured’ meats that still contain just as many nitrates via celery powder which doesn’t have to be labeled as such). However, the estimated relative risk is only 1.18 compared to 20 for smokers and lung cancer.

  14. It’s tough to have a good heuristic on this because observational studies can also go terribly wrong like the recent womens’ hormone replacement therapy debacle using observational studies that all the experts thought were the best that probably killed a couple tens of thousands until the proper RCT was run. As far as I understand, the evidence on smoking for a long time was not only observational but also not completely obvious (as obvious as it is today).

  15. After looking through the tobacco litigation docs I think it may have been because he did not know or suspect that nicotine was addictive in the modern sense of the word. He had of course suggested as an alternative cause that genetics led some people to smoke more and that those same genes likewise increased the risk of lung cancer thereby explaining the monotonic increase in risk seen as smoking (or bad gene prevalence) increased. He’s insistent that it’s not even a theory but at least a variable worth looking at when studies are done. I also thought this criticism of his interesting: “The writers do not understand what associations based on frequencies mean. To provide an explanation of the observed association, some cases must exhibit the correspondence; in others the causation may be quite different. The statistical aggregates available for examination will show associations due to any such cause, and these associations will be smooth and regular over a side range, merely because the observable are vaguely defined or observed, and show considerable overlap.”

    Anyway, here he is in 1962 going off about “the latest propaganda barrage”: https://www.industrydocuments.ucsf.edu/tobacco/docs/#id=zmbb0194

    Here you will learn that in 1962 Fisher was criticized in the House of Lords for “The theory of genetic susceptibility, which has been propounded by Sir Ronald Fisher, is not accepted by any other statistician in this country”: https://www.industrydocuments.ucsf.edu/tobacco/docs/#id=lrcx0209

    And finally here you will read the Tobacco Manufacturers’ Standing Committee fawningly tell Fisher that they don’t want to put words in his 72yr old mouth and then proceed to hand him a script – which he suggests they publish under their own name and then reiterates that he has “not put forward a theory. I have pointed to yawning gaps …” Don’t miss page the top of page 9 where Fisher shows a flash of the never faded anger at being called “not a statistician of note”: https://www.industrydocuments.ucsf.edu/tobacco/docs/#id=hfwh0209

  16. “Arthur Balfour Professor of Genetics”
    Funny how still today, climate change denialism is often linked to anarcho capitalists/social darwinists/eugenicists in mutual support with people meddling in the affairs of the middle east. :P

  17. 1) Big Tobacco (in US anyway) knew by 1953 the science was against them, hence big NYC meeting in NYC,
    https://en.wikipedia.org/wiki/Tobacco_industry_playbook

    2) It is well-etablished that people vary in development, adolescent brain development often continues into early 20s (AYAs = Adolescent/Young Adults), although almost all have adult brains by 25. For almost all, nicotine addiction only works during adolescent brain development. See annotated curve of 1st smoking age from 2015 National Academies (IOM) report:
    https://twitter.com/JohnMashey/status/826930267679895552

    3) Nicotine affects blood vessles, stiffening them, which doesn’t bother AYAs, but contributes to vasculate diseases (heart disease/strokes) later in life.
    (Unlike cancer & COPD, where damage already done, if one quits smoking, likelihood of vascular-related diseases decreases fairly quickly, some improvement after a few weeks.)

    4) If somebody wants to learn more about the biochemical mechanisms, Google:
    nicotinic acetylcholine receptors addiction OR
    nAChRs addiction

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