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Zoloft stories: Blackballed researchers and Correlation can imply causation

Frederick Crews is writing about selective serotonin reuptake inhibitors” (SSRIs):

Hence the importance of David Healy’s stirring firsthand account of the SSRI wars, Let Them Eat Prozac. Healy is a distinguished research and practicing psychiatrist, university professor, frequent expert witness, former secretary of the British Association for Psychopharmacology, and author of three books in the field. Instead of shrinking from commercial involvement, he has consulted for, run clinical trials for, and at times even testified for most of the major drug firms. But when he pressed for answers to awkward questions about side effects, he personally felt Big Pharma’s power to bring about a closing of ranks against troublemakers. That experience among others has left him well prepared to puncture any illusions about the companies’ benevolence or scruples.

. . .

The most gripping portions of Let Them Eat Prozac narrate courtroom battles in which Big Pharma’s lawyers, parrying negligence suits by the bereaved, took this line of doubletalk to its limit by explaining SSRI-induced stabbings, shootings, and self-hangings by formerly peaceable individuals as manifestations of not-yet-subdued depression. As an expert witness for plaintiffs against SSRI makers in cases involving violent behavior, Healy emphasized that depressives don’t commit mayhem. But he also saw that his position would be strengthened if he could cite the results of a drug experiment on undepressed, certifiably normal volunteers. If some of them, too, showed grave disturbance after taking Pfizer’s Zoloft—and they did in Healy’s test, with long-term consequences that have left him remorseful as well as indignant—then depression was definitively ruled out as the culprit.

Healy suspected that SSRI makers had squirreled away their own awkward findings about drug-provoked derangement in healthy subjects, and he found such evidence after gaining access to Pfizer’s clinical trial data on Zoloft. In 2001, however, just when he had begun alerting academic audiences to his forthcoming inquiry, he was abruptly denied a professorship he had already accepted in a distinguished University of Toronto research institute supported by grants from Pfizer. The company hadn’t directly intervened; the academics themselves had decided that there was no place on the team for a Zoloft skeptic.

That doesn’t make the research institute look so good, although maybe there’s another side to the story.

Hey, did he just say what I think he said???

Crews continues:

Undeterred, Healy kept exposing the drug attorneys’ leading sophistry, which was that a causal link to destructive behavior could be established only through extensive double-blind randomized trials—which, cynically, the firms had no intention of conducting. In any case, such experiments could have found at best a correlation, in a large anonymous group of subjects, between SSRI use and irrational acts; and the meaning of a correlation can be endlessly debated. In contrast, Healy’s own study had already isolated Zoloft as the direct source of his undepressed subjects’ ominous obsessions.

Thanks partly to Healy’s efforts, juries in negligence suits gradually learned to be suspicious of the “randomized trial” shell game. . . .

I agree that randomized trials aren’t the whole story, and I’ll further agree that maybe we statisticians overemphasize randomized trials. But, but, . . . if you do do a randomized trial, and there are no problems with compliance, etc., then, yes, the correlation does imply causation! That’s the point of the randomized design, to rule out all the reasons why observational results can be “endlessly debated.”

The New York Review of Books needs a statistical copy editor! I don’t know anyone there (and I don’t know Crews), but maybe someone can pass the message along. . . .

P.S. Maybe I’m being too hard on Crews, who after all is a literary critic, not a statistician. I assume he wrote this thing about correlation and causation because he misinterpreted what some helpful statistician or medical researcher had to say. Sort of like how I might sound foolish if I tried to make some pronouncement about Henry James or whatever.

P.P.S. Typo fixed (thanks, Sebastian).

7 Comments

  1. kholsinger says:

    Unless I'm misreading this phrase

    a causal link to destructive behavior could be established only through extensive double-blind randomized trials

    Crews could be arguing that randomized trials are not necessary to establish causal links. Whereas you argue that

    if you do do a randomized trial, and there are no problems with compliance, etc., then, yes, the correlation does imply correlation!

    i.e., that randomized trials are sufficient for correlation to imply causation. The two positions aren't inconsistent.

    Having said that, in the context of a population survey, I can't think of anything other than a randomized trial that would make it reasonable to infer cause from correlation. But even then it's dangerous to extrapolate that inference to the population other than the one(s) from which the sample was drawn.

  2. Anonymous says:

    But then Crews says, "In any case, such experiments could have found at best a correlation," which suggests that randomized trials (properly done) are not sufficient for showing causation. (Indeed, given the "at best" constraint, Crews may be going even further than that.) This does seem rather incompatible.

  3. Jeff says:

    But then Crews says, "In any case, such experiments could have found at best a correlation," which suggests that randomized trials (properly done) are not sufficient for showing causation. (Indeed, given the "at best" constraint, Crews may be going even further than that.) This does seem rather incompatible.

  4. sewenz says:

    Andrew,

    You might want to correct that (quoting from your entry):

    "[…] then, yes, the correlation does imply correlation!"

    The second "correlation" is a "causation", right? I mean, most people will get it. But, just in case…

    Best,
    Sebastian

  5. Radford Neal says:

    Here are some links to University of Toronto documents on this case, which caused quite a kerfufle here. My recollection is that the rescinding of the appointment occurred after Healy gave a lecture that some U of T faculty didn't like (seeing it as unprofessional or unscientific, I believe).
    Despite being at U of T, I have no personal knowledge that would allow me to comment on which side of the story is most correct.

    http://www.news.utoronto.ca/bin2/010907a.asp

    http://www.news.utoronto.ca/bin3/020426a.asp

  6. kholsinger says:

    Jeff wrote:

    But then Crews says, "In any case, such experiments could have found at best a correlation," which suggests that randomized trials (properly done) are not sufficient for showing causation. (Indeed, given the "at best" constraint, Crews may be going even further than that.) This does seem rather incompatible.

    I agree. That's why I wrote “Crews could be arguing…” rather than “Crews is arguing….” What Crews intended to say is incompatible with what Andrew wrote, even though what may not be.