Far more people think they are sick than actually are sick, mounting evidence shows, and a rising chorus of researchers are speaking out about overdiagnosis.

Overdiagnosis occurs when people are diagnosed and treated for conditions that will never cause them harm. It poses a significant threat to human health by labeling healthy people as sick and wasting resources on unnecessary care, writes Ray Moynihan, Senior Research Fellow at Bond University in Australia, on bmj.com, the web site of what was originally called the British Medical Journal. Moynihan and others cite several examples:

  • A large Canadian study finds nearly a third of people diagnosed with asthma may not have the condition.
  • As many as one in three breast cancers detected through screenings may be overdiagnosed, a comprehensive review concludes. Up to a fourth of breast cancers found through mammograms are harmless and wouldn’t cause noticeable disease during the women's lifetimes, a recent study from Norway suggested.
  • Osteoporosis treatments may do more harm than good for women at very low risk of future fracture, many researchers now argue.
  • Early detection of prostate cancer is men often does more harm than good, researchers say.

In September, researchers will hold an international conference called “Preventing Overdiagnosis.”

"As evidence mounts that we're harming the healthy, concern about overdiagnosis is giving way to concerted action on how to prevent it."

Many factors are driving overdiagnosis, including commercial and professional vested interests, legal incentives and cultural issues, say Moynihan and co-authors, Professors Jenny Doust and David Henry.

“It will be hard for doctors and the public to recognize that the earliest detection of disease is not always in the best interests of patients,” said Henry, chief executive officer of the Institute for Clinical Evaluative Sciences, and professor in the Department of Medicine at the University of Toronto, Canada.

Ever-more sensitive tests are detecting tiny "abnormalities" that will never progress, while widening disease definitions and lowering treatment thresholds mean people at ever lower risks receive permanent medical labels and life-long therapies that will fail to benefit many of them.

Added to this, is the cost of wasted resources that could be better used to prevent and treat genuine illness.

But Moynihan argues that the main problem of overdiagnosis lies in a strong cultural belief in early detection, fed by deep faith in medical technology. "Increasingly we've come to regard simply being 'at risk' of future disease as being a disease in its own right," he says.