A recent Third Circuit decision is a useful and quotable reminder that temporal correlation is not enough to prove causation.

Causation is an indispensable element of any product liability action. It is the same in pharmaceutical third-party payor (TPP) class actions, where it is often the element most likely to defeat class certification. Unsurprisingly, plaintiffs often employ creative workarounds in an effort to sidestep obvious causation problems. In In re Avandia Marketing, Sales Practices and Products Liability Litigation, — F.4th —, 2026 WL 2093904 (3d Cir. July 21, 2026), the Third Circuit made clear that there are no shortcuts.

According to the plaintiff TPPs, the defendant pharmaceutical manufacturer had marketed the medication at issue as not only treating diabetes but offering cardiovascular benefits too. The plaintiffs claimed that the promotional campaign caused physicians to prescribe the medication at inflated rates, forcing the plaintiffs to reimburse prescriptions they would not otherwise have covered.

Continue reading “Third Circuit Confirms Correlation Still Does Not Prove Causation”