A Discover magazine poll reported that 65 percent of those surveyed thought that nearly all of the health care they received is based on scientific evidence.

Yet a panel of experts convened by the Institute of Medicine, the health arm of the National Academy of Sciences, reported in 2007 that "well below half" of procedures and decisions about surgeries, drugs and tests have been adequately investigated, let alone shown to be effective. Some unknown proportion of these might have been avoided if proper research had been done.

When finally tested, many treatments are found to be useless at best or even harmful. When a new procedure or a new drug is developed, it might be used widely before doubts appear, and even then the needed research is often not conducted. Drug complications are responsible for more than 770,000 American injuries or deaths annually.

Physicians who have financial conflicts of interest with drug, device or equipment industries write many clinical guidelines. Authors of favorable articles concerning Avandia (a controversial diabetes drug) in medical journals were found to be three to six times more likely to have financial ties to the manufacturer than authors of those articles that were neutral or unfavorable.

Failing to give care that is needed or giving care that is not accounts for an estimated 30 percent of the $2.4 trillion spent annually in the U.S. on health care.

The FDA regulates drugs, devices and many tests but has no control over how doctors use them and has no control over surgical techniques.

Doctors are often as much in the dark as their patients when they perform surgeries, implant new devices or prescribe drugs.

Drugs must undergo many tests before they are approved, but many FDA studies are poorly designed or too small to answer important questions such as how often rare but harmful or lethal side affects occur and which patients are unlikely to be helped.

The FDA requirements are not particularly stringent. They only require that a drug is better than nothing. They do not have to prove that new drugs are an advance over older and cheaper drugs including some that are long proven to be safe. The FDA collects safety data on drugs, but only a fraction of potential harms and deaths end up in FDA databases because reporting is voluntary and because many trivial and unrelated events are thrown in with serious incidents.

The FDA does not routinely analyze reports for each drug or device, so it might miss serious side effects for years.

Doctors rely on procedures, tests and drugs that are not backed by sound evidence because most doctors are not trained to analyze scientific data, making it impossible for them to evaluate and interpret the results of medical studies. Medical students must memorize an incredible number of facts but do not have time to critique the information, and thus do not learn how to think critically.

This is not a matter of good or bad doctors. Rather it is a failure of our education system to teach critical thinking that permeates kindergarten through graduate school.