Analyses of scientific evidence led doctors to recommend that babies sleep on their backs.Credit: Yamaguchi Haruyoshi/Corbis/Getty
Beyond Belief: How Evidence Shows What Really Works Helen Pearson Princeton Univ. Press (2026)
Cementing the use of evidence in health and public policy has taken decades of challenging work. Fifty years ago, physicians commonly thought that babies should sleep on their fronts — advice popularized by US paediatrician Benjamin Spock and others. It took a synthesis of observations and case studies to show that this was wrong: babies should sleep on their backs to minimize the risk of sudden infant death syndrome (SIDS). More than 50,000 deaths across the United States, Europe and Australasia could have been prevented had this evidence been combined and put to use sooner.
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Beyond such data, the randomized controlled trial (RCT) is usually the gold standard for medical or public-policy evidence. Including a control group against which to compare interventions shows what would have happened without it. Combining many trials into a meta-analysis gives practitioners and policymakers more confidence in whether a drug or treatment works.
In Beyond Belief, journalist and science communicator Helen Pearson (who is an editor at Nature) presents an accessible account of how such practices spread. Covering topics from policing to child development, she focuses on outcomes that everyone cares about, be those safer neighbourhoods or better childbirth procedures.
This book is not a technical treatise, and nor should it be. As researchers know, the details of RCTs soon get technical once their basic principles have been explained. But Pearson pulls off a narrative feat. Anyone can read and enjoy the book, yet there are nuggets for experienced readers. The background research is impeccable. The only slip I noticed is the statement that “by 1964, around 25 out of every 1,000 children in the United States were dying from sudden infant death syndrome or SIDS” — in fact, this number is the rate of deaths from all causes, with SIDS being a small fraction.
Facing the facts
The book shares many examples of successes, in which solid evidence has corrected long-accepted bad practice. A 2002 Women’s Health Initiative trial1 showed that hormone replacement therapy (HRT), widely prescribed to prevent heart disease on the basis of previous observational studies2, actually increased the risk of cardiovascular disease and breast cancer.
Similarly, a systematic review of nine randomized trials3 done from the 1970s to the 1990s showed that an anti-crime programme adopted by many US states backfired in practice. Known as Scared Straight, the initiative involved sending children at risk of criminality into prisons to speak with incarcerated people. But, in the end, participants were more likely to offend than those in the control group.
A woman applies a hormone replacement therapy patch to her arm.Credit: Tetiana Melnyk/Getty
Pearson recounts horror stories from before RCTs took hold, such as episodes in which physicians withheld antibiotics for the treatment of early-stage measles, as was taught in medical schools before six RCTs showed that the drugs prevented fatal complications. Moreover, the two million arthroscopies performed worldwide every year were rendered largely unnecessary, given all the risk and cost that they entail, after a 2016 trial4 showed that this surgery performed no better than exercise therapy for treatment of torn knee cartilage.
Pearson has a good eye for the people involved, recounting vivid stories about how some scientists who championed RCTs were treated as mavericks and faced resistance to their ideas. Medical and public-policy practitioners often resented findings that challenged clinical judgement and professional autonomy.
These colourful characters include David Sackett, a “larger-than-life” US-Canadian pioneer of evidence-based medicine who rode a motorcycle while wearing purple overalls; Eric Barends, a champion of evidence in management studies, who gave up his house in Leiden, the Netherlands, to live in a converted bus that he shipped to California; and Lawrence Sherman, who joined the New York City Police Department as a researcher in 1971 and went on to invent evidence-based policing.
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Pearson devotes much space to women, including Esther Duflo, the second woman to win the Nobel prize for economics; Judith Gueron, a social-policy researcher who said that trials were “just like testing toothpaste” and fought sexism; and Denise Rousseau, a scholar of behaviour and public policy and one of the originators of evidence-based management. As in the rest of science in this period, there were fewer female leaders than male ones.
The author writes as a believer, and her passion is engaging. Readers of the book are even encouraged to join the evidence revolution. And who can argue against better evidence? After reading all of Pearson’s examples, it might sound odd to criticize the work of the heroes of this story. But it is easy to lionize the advocates and boo the defenders of the old ways when reality is more complicated.
Not all of the medicine practised before the era of RCTs and meta-analyses was a failure. Examples of such “eminence-based medicine” include defibrillation and insulin, which had demonstrable effects but were not rigorously tested. Pearson acknowledges the benefits of penicillin, which was never tested in a RCT.
