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This is the kind of research result that changes behavior.

Children whose mothers used acetaminophen during pregnancy were at higher risk for receiving a hospital diagnosis of hyperkinetic disorders or having attention deficit hyperactivity disorder-like behaviors at age 7 years. Stronger associations were observed with use in more than 1 trimester during pregnancy, and exposure response trends were found with increasing frequency of acetaminophen use during gestation for all outcomes (ie, HKD diagnosis, ADHD medication use, and ADHD-like behaviors. Results did not appear to be confounded by maternal inflammation, infection during pregnancy, the mother’s mental health problems, or other potential confounders we evaluated.

It is also the kind of research that I report here with both caution and trepidation. Say it with me: Correlation is not causation. Then hear the words of Kate Langley, a lecturer in the School of Psychology at Cardiff University in Wales, a co-author of an accompanying editorial for The Journal of American Medicine Pediatrics, where the study appears, urging caution in reading the results of a single study. The editorial also notes a few things within the methodology that emphasize the need to repeat the results in a different form of study. And it is even subtitled “An Interesting Observed Association but Too Early to Infer Causality.”

“This is an interesting research paper, but it is way too early for it to inform our clinical practice at the moment,” she told Time magazine’s Alice Park.

Doctors may not change the advice they give their patients, but patients are likely to change their behavior. If there is a pregnant woman out there willing to take Tylenol after reading this research — or just the associated headlines — I’d be surprised. Even given the caution regarding the research, that decision makes sense from the woman’s perspective. Researchers are cautious with respect to their results. Parents are cautious with respect to their babies.

Why the trepidation? Because I know how this research will make some mothers feel. (It is nearly always mothers for this kind of thing; seldom does the zeitgeist turn to questions like how a man’s consumption of over-the-counter pain relievers affects the quality of his sperm.) Correlation may not equate causation with respect to A.D.H.D.; it does with respect to guilt. As the writer Kristin Courtemanche told me by email, and later posted to her blog,