Relative Risks and Why Anecdotes Can be Lousy for Making Decisions

Fear blinds us, immobilizes us, and makes fools of us. Scary stories abound on the internet, through emails, and in conversations, and dangers lurk in the dusty corners waiting to pounce on us and tear our loved ones from our grasps. We know this. We feel it viscerally. And sometimes we shake in our boots. 

We've got enough real dangers, and we do, without adding in made-up ones. We do a terrible job at assessing risk. Don't believe me? Which is safer? Driving or flying? If you said driving, you're so terribly wrong and have let both the illusion of control and the availability heuristic make you run with your gut. 

If we admit this truth, that we are bad at assigning risks, then we should be looking for what science, statistics, and probability have to show on relative risks before we go off with our guts thinking we've chosen the least risky decision.

And I write this as a mom who lives this, every day. Your gut is not what you want to go with when you're making medical decisions. It isn't. You want some good hard data to back your decisions. My son has factor V leiden, a blood clotting disorder which caused a stroke when he was nine. At that time, once the doctors determined he had the disorder, we had to decide on preventative treatment. Do you give a nine year old coumadin for the rest of his life? Our doctor decided with one stroke to go on that the risks of coumadin were greater than the risks of another blood clot. Our son went on the less risky aspirin. If you have kids, you know that aspirin in children can be dangerous. It was a game we played, pulling aspirin when he had colds. Falls, bumps, bruises are scary. Will it lead to overclotting?  Bumps to the head? Beyond terrifying still to this day.

When he had his wisdom teeth out, he was sent to a hematologist for an alternative to aspirin in the weeks leading up to the surgery. The doctor was horrified that he'd been on aspirin for a decade instead of the standard coumadin and immediately wrote a prescription for that for after the surgery and one for lovenox injections leading up to the surgery. 

And I started digging through the literature, pulling up articles showing that where there had only been one incident (especially with a decade with no additional ones), that lifetime coumadin, indeed coumadin for one year, conveyed far greater risk (3 out of 100 patients have bleeding problems on coumadin in a year, with 1 death for every 200 patients on coumadin from excess bleeding). My son's real risk of a thrombolytic event was around 5 in 1000.  You can see right there that the risks were vastly higher on coumadin than off, and after consulting with an academic hematologist, my son's doctor deferred to his judgment and back on aspirin my son went.

When your family member's life is at stake, fear can be deadly, especially if it paralyzes you. It's incredibly hard to make sound, rational decisions when fear has coiled itself in your gut and twisted you in knots, so in order to be collected in crisis, you have to practice those reasoning skills in calm times. You have to look at the evidence dispassionately, and you have to defer to experts who know better. Sometimes that is indeed your immediate doctor, but even they can be paralyzed by fear and can make rash decisions. 

When you've got a chronic condition, you've got to become the expert on it because chances are your doctor or your child's doctor won't be, won't have the latest literature, and won't have thought out hypothetical situations before hand and will simply react, as my son's hematologist did.

It's okay, when it's not an immediate life or death situation to step back and say wait a minute, is that really standard of care? Is that what the guidelines call for? If you're deviating, what is your reasoning for it? It's hard to do, but it's your child's care.

The trick, though, is to find reputable sources, and just because it's on pubmed doesn't mean it's sound science or the standard of care. You have to ask questions calmly and you have to be willing to listen to the answers without letting emotion get in the way. If you're letting anecdotes guide your medical choices, you're not looking at the situation rationally and demanding proof. 

We need to embrace skepticism, and all the critical thinking tools at our disposal, in order to make good decisions, sound decisions, rational decisions for ourselves and our family members. If we can't do that when deciding on how to treat our children's colds and earaches and what preventative care we should use, then how will be able to do that when our child is seriously ill, potentially dying, and our decisions must be deliberate and rational? If you can't think critically on an easy day where it doesn't matter, how will you manage it when your life or your child's life does?

In writing about the vaccine fears, Daniel Gardner,  in The Science of Fear, page 107 wrote:

 “The danger here is that we will collectively cross the line separating skepticism from cynicism. Where a reasonable respect for expertise is lost, people are left to search for scientific understanding on Google and in Internet chat rooms, and the sneer of the cynic may mutate into unreasoning, paralyzing fear. The end state can be seen in the anti-vaccination movements growing in the United States, Britain, and elsewhere. Fueled by distrust of all authority, anti-vaccination activists rail against the dangers of vaccinating children (some imaginary, some real-but-rare) while ignoring the immense benefits of vaccination – benefits that could be lost if these movements continue to grow.”

I don't presume that I knew medicine better than the hematologist who reacted knee-jerk without considering the relative risks. I don't. Obviously. What I did know better that day, though, and in the subsequent time period of calmly convincing her that the numbers didn't support her treatment plan, was that ultimately, the buck stopped with me. I had to live with the decisions I made regarding my son's medical care and I had to do so with the most accurate, the best of, information. I am his mother and his legal guardian. I make the decisions he cannot make for himself and I have an obligation and a duty to do it well, to get it right. Fear gets in the way of that. 

What I have to fall back on in times of crisis is critical thinking skills, a whole bunch of tools to help me make the best decisions I can with the information I have. 

You should not decide to vaccinate or not to vaccinate based on anecdotes. You should not be swayed by anecdotes relating autism to vaccine injury, nor should you be swayed by stories of vaccine-preventable deaths. Anecdote doesn't give you the numbers. It gives you fear.

Sometimes you have to roll the hard six. Make sure when you do, you have the numbers behind you. What are the relative risks? Which is less risky? For some individuals, vaccines are too risky. These people rely on herd immunity. For most of us, the relative risks are less with vaccines than without. 

Say what you will about Penn and Teller, but their throwing balls at pins was an effective demonstration of relative risks. You have to decide do you have the balls, all of them, and can you effectively juggle them. Because if you're wrong, if you've gone with anecdote over science, you may have live with some spectacularly crappy results instead of shooting craps.


Lisa Jo Rudy said...

great piece, Kim!

I remember interviewing a police chief in a mid-sized town, who said the residents were very concerned about child abduction. I asked if there were many child abductions in the area, and he explained that there had once been one, but of course that was a case of an estranged father "kidnapping" his own child!

I know, too, how much more effective it is to tell ONE heartrending story than it is to dredge up pages of statistics.

"Millions displaced by floods" means nothing. The story of one family devastated by the floods is overwhelming.

As a writer, it's very useful to know all this - but a little disturbing, too.


Elise said...

Good post. I believe in doing your own researc too. My FIL was put on plavix which in rare instances of stroke causes brain bleeding, which is what actually happened to him and it was horrible until the decision was made to take him off life support. Whne myown fathr had a stroke my mother remembering wha happened refused to have my father put on plavix or any blood thinner. The neurologist then refused to treat my father in the hospital. I had to call his doctor to have him intervene. My father is now on a regular sized coated aspirin everyday instead of a blood thinner. WHile he may have a slightly higher risk fo stroke having watched the "rare" side effect of plavix at work, I feel better that my father woudl survie a stroke if god forbid he ever had another one. You know percentages are jsut percentages until it happens to you, then the occurrence is 100%.

On another issue anecdotal evidence. When I put my children on a modified gluen free diet, I thought teh psychiatrist was going to have a stroke...he was really annoyed wih me and said that there is no medical evidence that it does anythig, but if I insisted that it can't hurt them. Well, myown anecdotal evidence is that my odlest is difernt, calmer, more engaged in the world around him. Heck I even feel better and differnt. My youngest has had no change at all. My husband says he doesn't feel different either.

I am not sure that ignoring all anecdotal evidence is wise, sometimes things really are not quantifiable in statistics. Sometimes it really is just a feeling.(Of course we are also not talking about anything dangerous here either, so let me put that into persepctive too)

kathleen said...

Good post. Yes, we have way too many real dangers..and yet it seems that we feed the smaller ones. Bogey men-anecdotal monsters that are fed in chat rooms all over the net. Why is it easier to believe in a conspiracy theory than in scientific evidence? Is it because fear is something that can seemingly be controlled? Lots to think on-thanks..:)

Sirenity said...

Well done Kim
Amazing isn't it, how we have to guard against falling for that 'gut feeling'.
I am also impressed that you are having such amazing luck lately at having commenters prove your points for you...Nice!

Elise said...

Apologies for the really bad typos above. Editing obviously is not my strong suit without spell check.

Roger Kulp said...

This was the second time I had read about Factor V Leiden in your blog.As you know,I was diagnosed last year,as being double heterozygotic with MTHFR polymorphisms,on both genes.I have a history of heart failure that started in my teens,megaloblastic anemia,arteritis/SLEs,with systemic edema,that started when I was nine,as the main MTHFR problems.

As you may know,the genes for both Factor V Leiden,and MTHFR,are both on chromosome 1.I didn't know this about FLV,until I did some Googling,but after what I have had to learn about MTHFR,I suspected as much.Both are usually only diagnosed in pregnant women. It seems to be fairly rare that either are diagnosed in males,even with autism.We know about MTHFR in autism,although few autistics seem to be as sick as I am,but other clotting,or blood disorders caused by chromosome 1,seem to be largely undocumented.I think THIS would be a very interesting subject for further study.

This is a fairly rare condition.What would you have done if the doctors never found the cause,or your son was misdiagnosed,and my not have died,but had one close call after another,and just got sicker like I did? If all you have is an autism diagnosis,and a lot of other mystery symptoms,you are pretty much SOL.You can understand how people are driven to this vaccine crap,by doctors who don't do enough of the right tests.

Would you have been drawn into the vaccine morass,if everything was the same,and your son was 5-10 years older?

Have you ever considered looking into the possibility your son has deletions,mutations,duplications,etc on either chromosome 16 or chromosome 22 ?

It's kind of creepy to have a genetics doctor look at your genes,and say how weird it is you are neither nonverbal or intellectually disabled.

Congratulations on the award,it just confirms what we know already.

Roger Kulp said...

I meant younger,duh.

KWombles said...


Understanding human psychology and that we simply aren't equipped to resonate with large numbers, providing specific examples is necessary for emotional reaction and then action. And so, good writers and good cons (too) use that anecdote to move the audience to action.

It is precisely why medical decisions should never be made through personal anecdotes (and perhaps financial decisions, as well, since it's easy to fool people).


Being an informed consumer is key. And don't worry about the typos; I make them all the time. :-)

Sirenity and Kathleen,



I don't know if he'd been my girls' age and we were freshly facing this how it would be different for me. I'd like to think that were it happening now and I was equipped with what I know, then no, I wouldn't go that route. But I don't know that for sure.

The doctors explored every possible reason for the stroke, and at the time, Factor V was newly discovered. I've never had a doctor ever look at my children's autism as a reason not to explore their medical issues. Ever. I've had a fair amount of docs make mistakes and errors of judgment, but not refuse to treat based on an autism diagnosis.

I have tremendous empathy for parents who face these challenges and who are not equipped with the tools or with sensitive doctors who take the time to explain their child's diagnosis better.