People who don't know they have health problems rate their own health as good, according to a new study, but their self-image worsens when they're aware of their diagnosis.
Based on a large population survey in Norway, the authors say that increased use of screenings, more sensitive tests and widening diagnostic criteria may cause unexpected harm because poor self-rated health is tied to a greater risk of death.
Although early detection of disease can be important for treatment, the authors write in the journal BMJ Open, "disease-labeling" may cause problems by altering a person's perception of their own wellbeing.
"We know ever more people are being labelled, owing to more screening, lower diagnostic thresholds, commercial - and non-commercial - health campaigns and so on," Pal Jorgensen said. "Self-rated health is shown, several times, to be inversely associated with mortality."
Jorgensen, who led the new study, is a public health researcher at the Norwegian University of Science and Technology in Trondheim.
"It is also an important aspect in the increasing attention and discussion of overdiagnosis; people being labelled with disease, but where treatment does not lower mortality," Jorgensen told Reuters Health in an email.
Overdiagnosis generally refers to diagnosing and treating early or minor conditions that may never have progressed to cause a problem. This can include the controversial practice of diagnosing "pre-disease" states, such as slightly elevated blood sugar that falls short of diabetes.
To gauge the effect of being diagnosed with disease on a person's perception of their own health, Jorgensen and his colleagues analysed data on 33,734 adults between the ages of 40 and 70 who were surveyed and medically tested in the mid-1990s in Norway.
The researchers were interested in connections between how the participants answered the simple question "How is your health at the moment?" and whether or not they were aware of having specific health conditions, including diabetes, thyroid disease and high blood pressure.
The researchers used the medical testing data to determine if people actually had any of those three conditions, and found that people with diagnosed illness were less likely to say they were in good health.
But people with undiagnosed illnesses were more likely to say their health was good than people without those illnesses.
For instance, women who knew they had hypothyroidism were less likely to report good health than women without thyroid disease, but women who didn't know they had thyroid problems were 84 per cent more likely to believe they were healthy than women who didn't have thyroid disease.
Similarly, people with undiagnosed severe hypertension were more likely to report good health compared to participants with normal blood pressure readings.
And, in general, participants who didn't know they had diabetes or mild to moderate hypertension were just as likely as people without the disorders to believe they were in good health.
"We were surprised that many persons with disease, without knowledge about this fact, reported their self-rated health as good, sometimes even more often than healthy people," Jorgensen said. "The fact that persons with acknowledged disease report their health as poor was not unexpected."
It's important to note that the study relied on self-reported information, which may not be completely accurate, and that studies like this can't prove that knowing about a health condition actually causes a person to feel they're in poor health, the authors caution.
It's possible that people who don't know about their conditions are more optimistic and worry less in general so they're just less likely to go to the doctor for check-ups or when they have vague symptoms, Jorgensen and his colleagues write.
Jorgensen said that people should be concerned and ask critical questions, like whether health screening will do them any good or improve their chances to live longer.
"The main effects of check-ups are more people defined as sick, more people undergoing treatment, without lowered mortality," he added.
Dr. Otis Brawley, chief medical officer of the American Cancer Society and author of "How We Do Harm: A Doctor Breaks Ranks About Being Sick in America," told Reuters Health the researchers are right on target.
"We've got data to show that depression and suicide increases in men who are known to have an elevated PSA, not men who have prostate cancer but men who have an elevated PSA that merits an evaluation for prostate cancer," he said.
People think early detection can only be good and they don't know that giving someone a diagnosis or label can be harmful, he said.
"So I think we need to think about these things, but we also need to have a more positive attitude about the early detection of some of these diseases," he said.
Neither expert suggested that genuine illness should go untreated.
Brawley said he would prefer that a patient and doctor know about any health problems so they could work through them.
"If I've got someone who's got mild diabetes or metabolic syndrome I might actually be able to work with that patient and actually get them to a near-normal state," he said.