(cross posted at freeforall)
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. 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.
The problems of over-diagnosis include health impacts of treatments, stigma from labeling, worry and cost. The essence of the problem is that these costs (monetary and intangible) are increasing while the benefits of any treatment available are not (mortality reduction, morbidity decline). The figures from the paper provide examples in which death rates from certain Cancers are stable over time, while cases are increasing, typically due to improved ability to detect disease and/or more attempts to do so via broader screening. Below I reproduce just one of the 5 graphs demonstrating this phenomenon with Thyroid Cancer: