Author replies: Prof Scott O. Lilienfeld replies on myths about mental illness and violence


You may recall a previous post about myths regarding mental illness and violence.

All authors get immediate right of reply, so I am grateful to get Prof Lilienfeld’s comments in reply which I post below:



A colleague alerted me to this blog post and Dr. Thompson kindly informed me about it as well, and asked me if I’d care to respond. I’ll be more than happy to do so.

I apologize in advance if my tone is a bit harsh. But I have to confess that I found it extremely challenging to respond to Dr. Thompson’s blog post. Why?

It is one thing to respond to a substantive criticism of what one has written; it’s another to respond to a criticism of something that differs entirely from what one has actually written. In this case, Dr. Thompson’s blog addresses a very different question from that posed in our book. As a consequence – and I’m sorry that I can’t find any more delicate way to put it – his blog post is more or less one extended non sequitur. It addresses an interesting and important question, to be sure, but it is most certainly not the question we raised.

In short, Dr. Thompson’s method of argumentation appears to be as follows:

(1) The authors (in this case, us) claim that Statement A is a myth.

(2) I don’t agree that Statement A is as important or relevant as they do, and I wish they had instead addressed Statement B.

(3) Data indicate that Statement B is not a myth.

(4) Hence, Statement A is not a myth.

To be frank, I had to read the blog post several times to make sure that I wasn’t missing something, but I’m not. That is indeed Thompson’s line of argumentation.

To be clear, what we wrote is that the assertion that most mentally ill people are violent is a myth (people can legitimately question whether this is a commonly held myth among the general public, but numerous media and political conversations in the U.S. arising from recent mass shootings by apparently mentally ill individuals have referenced this claim or ones very much like it: We did not question whether mental illness is linked to a higher risk of violence; in fact, in our chapter we acknowledged that this link exists, and we described it as “modest” in magnitude (to his credit, Thompson acknowledges this point). One can legitimately question whether “modest” is too tepid a descriptor, but please see this recent (2012) study (, and the authors’ conclusion:

“..there is a statistically significant, yet modest relationship between SMI [serious mental illness] (within 12 months) and violence, and a stronger relationship between SMI with substance use disorder and violence.”

In any case, I (we) did and do not question Thompson’s conclusion that severe mental illness is tied to a heightened risk of violence, although at least some of this link appears to be mediated by substance abuse. In fact, in a chapter that Thompson does not cite, I reviewed and discussed Teplin’s 1985 study in my 1994 book, Seeing both sides: Classic controversies in abnormal psychology:

There, I discussed some of the same sticky inferential issues regarding covariate control raised by Thompson (good lesson to blog posters – before criticizing authors, do your homework).

So, to summarize, in our book we argued that the claim that most mentally ill people are violent is a myth. Thompson then argued that he wished we’d discussed a different claim, namely, that mental illness isn’t associated with a heightened risk of violence, and he instead rebutted that second claim. In doing so, he reviewed evidence that actually supported our claim (!), but that rebutted his preferred myth, and then remarkably – in a bait-and-switch that would make advertisers envious - concluded that “So, the myth is not a myth: schizophrenic patients are roughly 5 times more violent than the general public” (!). The first part of that sentence is simply (and wildly) wrong: Our myth is indeed a myth.

In addition, to the logical errors (readers who enjoy collecting logical fallacies might also want to try to spot a striking example of the genetic fallacy in his blog post; see in his column, Thompson seems to fall prey to the commonplace error of confusing relative with absolute risk ratios (see the following article for an excellent review of this and similar topics: Specifically, the fact that schizophrenia is associated with a several times higher risk of violence does not imply, or come remotely close to implying, that most people with schizophrenia are violent. To do imply thus would be to fall prey to the related error of base rate neglect, as the base rate of schizophrenia in the general population is probably a bit under 1 percent.

Similarly, imagine that one were to maintain that (a) “Most people who smoke cigarettes do not get lung cancer” (certainly true, by the way… and that Thompson (or someone else) were to take issue with this claim on the grounds that (b) cigarette smoking is associated with a heightened risk of lung cancer. Again, such an argument would constitute a glaring non sequitur. The data presented in b in no way refute a, because the base rate of lung cancer in the general population is relatively low on a statistical level (although of course extremely high from the perspective of tragic human and societal costs – alas, statistical formulas are heartless and do not care about such matters).

Finally, Thompson’s argument about invoking myths, following the late Buzz Hunt of intelligence research fame, strikes me as quite unconvincing (one hears such arguments against invoking myths from time to time, although I’ve never been persuaded that people who advance them actually believe such arguments when the rubber means the road in actual practice). If one can make a claim that X is true, as Thompson himself is doing here, one can also make an equally compelling claim that not X is false. To be sure, some “myths” contain a kernel of truth (hence, such myths fall on a continuum with accurate information, as we acknowledge in our book), but many are flatly wrong. The sun does not revolve around the earth; the brain does not serve as a radiator, as the great Aristotle believed; people do not use only 10 percent of their brain power; water does not retain a “memory” of molecules that are no longer present in it (as homeopathy proponents claim); and so on.

Thanks again for the opportunity to respond; I’m sorry that I found the quality of Thompson’s blog posting to be disappointing.

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