Medicine’s much hailed ability to help the sick is fast being challenged by its propensity to harm the healthy. A burgeoning scientific literature is fuelling public concerns that too many people are being overdosed,1 overtreated,2 and overdiagnosed.3 Screening programmes are detecting early cancers that will never cause symptoms or death,4 sensitive diagnostic technologies identify “abnormalities” so tiny they will remain benign,5 while widening disease definitions mean people at ever lower risks receive permanent medical labels and lifelong treatments that will fail to benefit many of them.3 6 With estimates that more than $200bn (£128bn; €160bn) may be wasted on unnecessary treatment every year in the United States,7 the cumulative burden from overdiagnosis poses a significant threat to human health.

Narrowly defined, overdiagnosis occurs when people without symptoms are diagnosed with a disease that ultimately will not cause them to experience symptoms or early death.3 More broadly defined, overdiagnosis refers to the related problems of overmedicalisation and subsequent overtreatment, diagnosis creep, shifting thresholds, and disease mongering, all processes helping to reclassify healthy people with mild problems or at low risk as sick.8

The downsides of overdiagnosis include the negative effects of unnecessary labelling, the harms of unneeded tests and therapies, and the opportunity cost of wasted resources that could be better used to treat or prevent genuine illness. The challenge is to articulate the nature and extent of the problem more widely, identify the patterns and drivers, and develop a suite of …