Evaluating Evidence: Acetaminophen and Herbs

In light of the recent announcement from the US President about acetaminophen and autism spectrum disorder (ASD), I wanted to take a moment to comment on evaluating evidence. Although the subject may seem completely different from most of my blogs, the process of weighing scientific claims is relevant to how we think about herbs and health decisions in general.

Unfortunately, we usually hear health or science claims as black-and-white — ‘X causes Y’ — while the uncertainty in the middle often gets left out. During my training in epidemiology, I was taught about this uncertainty as the “black box,” where an association exists between two factors, but the pathway linking them is still a mystery. So we see the “X” (exposure) and the “Y” (the outcome of interest), but everything between these two factors is hiding in the black box. Think of a light switch on the wall (X) and the illumination of a bulb (Y) — so much more is needed to illuminate that bulb than the flipping of a switch, although most of the mechanisms are hiding behind a wall (or coming from a power company).

Regarding the recent acetaminophen-ASD announcement, an important consideration is that the recent “study” described by the President is actually a review of other studies. Systematic reviews are often used to summarize information when numerous studies have been conducted to try and find a relationship between an exposure and outcome. They are useful for identifying patterns and weighing the strength of evidence across multiple studies, but they don’t generate new data themselves — and the quality of the review depends on the quality of the studies it includes. (In some cases, this can be described as “garbage in = garbage out”.) I haven’t had the opportunity to evaluate the studies that were included in this recent systematic review, but I have evaluated enough systematic reviews to know that it is rare to come to a definitive conclusion of causality, especially when the studies have different conclusions. If the relationship between acetaminophen and ASD were clear, there wouldn’t be a need for a systematic review.

When scientific findings are presented as absolute, it’s easy to forget that science usually unfolds gradually — one study builds on another, and consensus emerges only after repeated testing, replication, and careful evaluation. This is especially important in health decisions, whether we are talking about medications like acetaminophen or herbs and natural remedies.

For example, some herbs have centuries of traditional use, along with modern studies suggesting potential benefits — but rarely is the evidence truly definitive. Just as with the acetaminophen-ASD question, we need to consider the totality of evidence, recognize what is known and unknown, and understand that the “black box” often still contains many unanswered questions.

This doesn’t mean ignoring risks or benefits — it means staying thoughtful and evidence-aware, considering study quality, reproducibility, and plausibility. It also means recognizing that early findings can be uncertain.

By thinking this way, we can make informed decisions without overreacting to headlines or dismissing useful information. Whether evaluating acetaminophen or an herbal remedy, a careful, curious approach helps us navigate uncertainty safely.