Zoloft MDL Excludes on Daubert Grounds Plaintiffs’ Experts’ Opinions on General Causation

Last month the Pennsylvania federal judge presiding over the multi-district litigation in which the plaintiffs allege that the prescription anti-depressant Zoloft, taken during pregnancy, causes birth defects, issued another in an series of Daubert rulings on the plaintiffs’ proposed experts as to general causation. Although the defendant conceded the qualifications of the three research scientists whose expert evidence was being tested, the reliability of their general causation opinions was hotly contested and received a full evidentiary hearing.

The Zoloft court’s rulings represent an important addition to the Daubert jurisprudence that has cut into the plaintiff’s bar’s ability to advance contrived mass, toxic tort litigation in the areas of prescription and over-the-counter medications.

The court first addressed the scientists’ opinions as to whether there is a plausible biological mechanism by which the drug could cause the birth defects and whether the drug causes injury when taken appropriately by women during the first trimester of pregnancy. One of the researchers that reviewed in vitro studies conducted by others, and who concluded that there is a plausible mechanism of action by which the anti-depressant might impact embryonic development, was challenged on the grounds that he had not conducted his own peer-reviewed animal study. The court rejected this challenge because there had been a full consideration of pertinent hypothesis testing done by others. The court  addressed in the opinion the supporting evidence and explained why contradicting evidence did not undermine the researcher’s opinion.

A second researcher’s opinion on plausible biological mechanism was accepted in part and rejected in part.  The court allowed that  portion of the expert’s opinion that was based upon well-established effects of the drug’s action on laterality defects (i.e. abnormal location and function of organs) in animal embryos,  but it rejected the opinions that were based upon a theory about which the researcher admitted during deposition that the scientific field was in disarray as to understanding.

The researchers’ opinions on human causation, however, fared more poorly for a number of reasons. Although the drug had been being prescribed for decades, and thus there was ample epidemiological research on its use during pregnancy, the researchers nonetheless neglected to analyze the strengths and weaknesses of the evidence that was inconsistent with their causation opinions and failed to explain why that contrary research did not undermine their conclusions. Furthermore, the researchers’ methodologies were found to be significantly flawed to the extent that there was extrapolation from effects found only at extremely high doses to a conclusion that the drug significantly increased risk of defects at all conventional doses.

This finding was reminiscent of one of the grounds for the successful challenge to the plaintiffs’ experts  in the Denture Cream MDL. In that litigation, in the context of a  case involving a woman who had used three-fifths of a pound of denture cream every week for eight years to hold her dentures in place, the court excluded her proposed experts because they failed to establish how much zinc caused a purported reduction in copper or how much reduction in copper for how long would cause the alleged harm.

Further shortcomings with the Zoloft plaintiffs’ general causation case included failure to conduct or even adequately to address studies done on live mammals, which was found to be problematic because of the known shortcoming in studying drugs’ effects in vitro or on most egg-laying animals because the medication is not first metabolized by the mother before it affects the embryo.  The experts were also faulted for being unable to show quantitatively the level of alleged disruption of the particular neurotransmitter because there was no data developed or analyzed regarding the ideal ranges of the substance in pregnant women.

On these grounds the proposed experts’ opinions regarding general causation of injury in humans were rejected with the remark that even talented scientists cannot be permitted to provide the jury with unscientific speculation.

The Zoloft court’s rejection of the plaintiff’s “junk science” on general causation, which builds on and adds to similar previous defense successes, including the Chapman decision in the Eleventh Circuit, which echoed upon District Judge’s observation regarding the inadequacies of the novel science advanced by the plaintiffs that although the record contained enough scientific data to hypothesize causation, there was not enough to infer it because “hypotheses are verified by testing, not by submitting them to lay juries for a vote.”  Slip op. at 28.  Zoloft and Chapman, as well as decisions from the Seroquil and Ephedra  litigations, (McClain v. Metabolife Int’l, Inc., 401 F.3d 1233 (11th Cir. 2005)), can be used to help persuade district courts to perform similar painstaking Daubert analyses where plaintiffs’ experts hypothesize on general disease causation but never themselves submit their hypotheses to comprehensive examination.


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