Doctors used to decide how to treat patients using only their own judgment and experience. We now know that this is not the best way to practice medicine. This is because what doctors think is best for a patient is not always what is best when you actually look at the research.

When researchers study a disease or a condition, they look at many more patients than your doctor will ever treat. Also, medical knowledge changes all the time. And what doctors used to think was the best thing to do even a few years ago, might actually be considered harmful today. (To find out more about this, see Why evidence from research is so important.)For example, we know now that it is important to look at the best evidence from the research in order to make decisions about treatment. Using research in this way is practicing what is called evidence-based medicine. Evidence-based medicine looks at all the evidence that there is in the whole world, not just the evidence found in a few papers published in the big, easy-to-find medical journals. Only by looking at all the evidence and judging it fairly can you work out what the research really says about a treatment. We also know that to come up with the best treatments for individual patients we need to balance what the research tells us with doctors' experiences of treating a condition and with the values and preferences of patients.¹ Consumer Reports Health.org is based on information from Clinical Evidence, a book and online resource written for doctors by experts from all over the world. These experts look at all the evidence for a treatment. They weigh it carefully and decide which treatments work and which don't work. They include research studies that have been published and those that haven't been published. This is what evidence-based medicine is: a way of looking at and valuing all of the research about a condition and its treatment. The experts also look at the side effects of treatments. As new studies get published, the Clinical Evidence team updates its listing of studies. And the results of these new studies are evaluated regularly.

• All evidence is not alike. Some evidence is better than other evidence.
• When doctors looks at the research before recommending a treatment, they are using evidence-based medicine.
• Evidence-based medicine looks at all the research that there is about a disease or treatment.
• When researchers look at whether a treatment works, they look at many more patients than your doctor will ever treat.
• Sometimes the evidence can't tell you which treatment is best for you, so it's important that you weigh the benefits and harms of treatment carefully.

Clinical Evidence is published by the BMJ Publishing Group, an independent company that has been publishing information for doctors for 160 years. It is based in the United Kingdom, but one-third of its expert researchers and editors are from the United States. Consumer Reports Health.org provides you with the same high standard of information as you find in Clinical Evidence. So you can see the information that your doctor uses to make decisions about your treatment. Not all information from research studies is accurate. That's why Clinical Evidence sifts through all the studies about a treatment to find the best ones. All evidence is not alike. It can be dangerous to rely on what your neighbors or friends tell you. For example, just because a cancer drug worked for them does not mean it will work for you. Also, there have been many practices in medicine that were later found to be useless or even harmful when studies were done.Here are some examples:

• Fifty years ago, women who had babies were often given an enema while they were in labor. This is uncomfortable and unpleasant. But it was done because doctors thought that by giving women enemas they would be less likely to get an infection and so would their babies. Some hospitals gave soapy enemas. These gave women cramps. When doctors studied the results from the research, they found there was no evidence that enemas prevented infections. Two studies actually showed that enemas made more of a mess, and women felt embarrassed by the enema.² Women no longer have enemas while they're in labor because enemas don't keep infections away.
• Early in the last century, babies' mouths were cleaned regularly because it was believed that this got rid of germs. Only later did people realize that this cleaning caused ulcers on the roof of babies' mouths.
• Resting in bed used to be recommended for many conditions. But now we know that it can often do more harm than good. People who have had a heart attack, for example, do better both physically and mentally if they begin exercising as soon as they feel well enough instead of staying in bed for months.
• Many children used to have their tonsils removed to keep them from getting throat infections. The operation is rare now, because the risk of complications from surgery makes it likely to do more harm than good.

Sometimes research has proven that a treatment works, but the medical field has been slow to start using the treatment. For instance, tens of thousands of premature babies died because medication that could help them breathe better was not widely used. In 1972, the first of several studies was published showing that giving drugs (called corticosteroids) to women about to have a premature baby could help the baby's breathing.³ However, it was another 20 years before obstetricians began using these drugs regularly. When you aren't well, your family and friends often give you advice and tell you about their experiences. These stories can be very powerful. If your mother says that your daughter has had so many sore throats that she needs to have her tonsils taken out, you may believe her because she is your mom. She may say that when you had your tonsils out you stopped missing school and started eating better and growing more. But many thousands of children have their tonsils out each year, and there is no evidence from research studies that it does them any good at all. Some even get complications from the surgery, such as bleeding. Your mom means well, but one person's story is just that. It is the story of one person who had a treatment. It is not the story of thousands of others who have also had it.For example, you often hear stories of people who have survived cancer because they went on strict diets. However, you are less likely to hear about people who went on strict diets and died. They are not around to tell their stories. It can be hard to follow a strict diet if you have cancer and find it hard to eat. It may keep you from enjoying your life. You should think carefully before you start a diet that is difficult and unpleasant to follow and do it only if you will get some real benefits from it.Imagine you have a neighbor, Jean, who is sure that a new health supplement advertised on television helped her osteoarthritis. She says that a few days after taking it the pain in her knees got better. Maybe the pain did get better because she took the supplement. But you can't be sure. Sometimes the pain from osteoarthritis gets better and then gets worse over a few days. Jean might have gotten better anyway. What if she keeps taking the pills and a year later she has a heart attack? Did the pills cause her heart attack? Unless you look at what happens to lots of people taking the supplements, you can't know if they cause heart attacks or not. Jean's heart attack may have nothing to do with the supplements.But you can learn a lot from one person's experience of treatment. Research studies do not always look at the things that matter to patients. What friends and neighbors and other patients with your condition say is important. But you shouldn't use this information on its own when you make decisions about treatment. It's tough for busy health professionals to keep up to date with advances in medical knowledge. A doctor would have to read 17 articles in medical journals every day of the year to keep up with new information in his or her area of practice.⁴More medical information is now available in shortened or summarized forms to make it easier for doctors to keep up to date. But not all doctors use these new forms of information. Many studies show there is a big difference in how conditions are treated across the country.⁵Sometimes there is more than one treatment for a condition. This is why your values, and what you want out of your treatment and your life, are so important. At the moment, the treatment that you are offered seems to depend more on what local doctors want and less on what their patients want.For instance, if you have a type of chest pain known as angina and live in New Haven, you are twice as likely to be offered a bypass operation as you are if you live in Boston.⁶ Physicians in Boston seem to prefer giving patients medication for angina. But if you have osteoarthritis in your hip, you are more likely to be offered a hip replacement if you live in Boston than if you live in New Haven.⁶If you have prostate cancer, your choice of treatments is even more complicated. Some doctors recommend surgery, others recommend radiation therapy and some think you will do just as well without any treatment.⁷When there is no right answer, you need to make sure you understand the risks and benefits of the treatments being offered to you. Your doctor may be an expert in his or her field. Or he or she may decide how to treat you based on what the experts say. Much of what doctors learn at medical school is based on what experts think. Doctors like to ask their colleagues for advice.But experts don't always get it right. It is safer to rely on the results of good research studies than on one person's opinion, regardless of how well known they are. A few decades ago, medical experts said that all pregnant women should have X-rays to measure their pelvic bones. They wanted to do this to make sure the babies had enough room to get out. We now know this practice does more harm than good. It is not good to give radiation to an unborn baby. Every day there are stories in newspapers or on television about the latest discoveries in health care. One day you may hear that drinking alcohol keeps you from getting heart disease. The next day you may hear that it can make it more likely that you will get breast cancer. What should you do? The media often report on the results of just one study. There may have been other studies that had different results, and the reporter may not know about these. Usually, any one study just adds a brick into a growing wall of evidence. The results of one study cannot tell you the whole story. It is only after other groups of researchers repeat the study and find the same results that answers become reliable.You do not need to make a decision on the basis of one study. The media also tend to be optimistic about advances in medicine. A study that looked at how the media reported on drug treatment for osteoporosis and high cholesterol found that the benefits were stressed but the harms of the drugs were barely mentioned.Drug ads can be incredibly persuasive. Because drug companies are trying to sell their drugs, they stress the benefits and gloss over the harms. Just because something has been used for years doesn't mean it works or can't hurt you. Many complementary and alternative medicines have been used for years. But there isn't good evidence that they do more good than harm.One study looked at seven reference books.⁸ It found that more than 100 different complementary medicines were recommended for asthma. But there was no good evidence that they worked.Traditional remedies may have been used for centuries, but they may not be safe when taken with modern medications. St. John's wort, for example, is an herbal remedy for depression. Unfortunately, it stops some other drugs, such as the birth control pill and blood-thinning tablets, from working properly. Here are some questions that might help you weigh the information you find in the media or on the Internet about treatments. You could show these questions to your doctor.

• How could this treatment help me? Has it been studied in people like me? (For example, drugs are often tested in men rather than women.)
• Is it likely that this drug will hurt me? Am I more likely to get side effects than other people? (For example, older people sometimes have more side effects.)
• Who is telling me about this treatment? Is there a reason they want to tell me how good it is? (Sometimes doctors are paid by companies to say good things about their drugs and products.)
• How strong is the evidence that supports the claims being made about this treatment? Are the results published in a medical journal? Is just one person telling their story on television?
• What are the alternatives to the treatment being offered?
• What are the costs of the treatment? (These can include the cost of inconvenience, not just financial costs.)