Doctors prescribed it to 15 million women. The science said it prevented heart disease. The science was wrong.
For decades, hormone replacement therapy was the standard of care to prevent heart disease in postmenopausal women. Observational studies showed clear benefits: women taking HRT had lower rates of coronary disease. It made biological sense—estrogen reduced bad cholesterol.
Then in 2002, researchers did what nobody had bothered to do: they ran a proper randomized trial.
The result shocked medicine. HRT didn’t prevent heart disease in older women. It caused more heart attacks, strokes, blood clots, and breast cancer than placebo.
The correlation was real. Women on HRT did have better health outcomes in observational studies. But it wasn’t the hormones protecting them—healthier, wealthier women were simply more likely to choose HRT. They were already at lower risk. The therapy was just along for the ride.
Between 2002 and 2012, an estimated 50,000-91,000 women died prematurely from the aftermath of this confusion—some from taking therapy that harmed them, others from stopping therapy they actually needed.
And here’s what should terrify all of us: we’re making this exact mistake right now.
We credit our new campaign for the sales spike. But our competitor went bankrupt the same week. We scale the budget. Six months later when we face real problems, we keep doubling down on a campaign that never actually worked.
Same pattern. Same expensive mistake. Different industry.
$37 billion gets wasted annually on marketing budgets alone because people can’t tell the difference between correlation and causation.
This week’s Thinking 101 episode gives you the framework to stop making this mistake: five core strategies, one powerful question, and a practice exercise you can use immediately.
✅👉 Watch: ‘How to Master Causal Thinking’ - https://youtu.be/9TaG4msX9MY
Because right now, while you’re reading this, someone just approved a million-dollar budget based on a correlation they mistook for causation.
The only question is: will you be the one who catches it?
Episode 3 of Thinking 101 Series. Cross-posted from Phil McKinney’s Innovation Studio YouTube Channel. Subscribe at youtube.com/@PhilMcKinney