Overdiagnosis

Overdiagnosis happens when screening or testing finds real abnormalities that were never destined to cause symptoms, disability, or death. It differs from a false positive: the disease is genuinely present, but it would have remained harmless. Because those cases get counted and treated, screened groups can show more diagnoses and better-looking survival without fewer deaths overall. When reading a study, ask whether a screening test increased the number of diagnoses without a matching drop in disease-specific mortality, and whether long-term follow-up tracked deaths from all causes rather than just survival after diagnosis. A classic illustration is screen-detected slow-growing tumors that never would have progressed: catching them inflates incidence and can trigger surgery or radiation with no gain in lifespan. Watch for reports that emphasize five-year survival or earlier detection while staying quiet about whether total deaths changed. That gap is where overdiagnosis usually hides.