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How We Weigh the Evidence

If you're going to make informed healthcare decisions you need good information.

But how do you know that what you're being told is true? How do you weigh the evidence?


While it's often helpful to hear what other people have to say, they may be telling you something based on their personal experience or beliefs. But that's not evidence.

The best evidence is based in research. You will need to know how to critically look at the evidence. The information below can help.

Our evidence pyramid visually depicts the strength of evidence from different research designs.

The image below is one of several available renderings of an evidence pyramid. Studies with the highest internal validity, characterized by a high degree of quantitative analysis, review, analysis, and stringent scientific methodology, are at the top of the pyramid. Animal and laboratory studies reside at the bottom of the pyramid.


Editorial and expert opinions - while they may be informative - are not considered evidence.

We believe in evidence-based medicine, not "eminence-based medicine."
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Problems with the Evidence

Many of the problems attributed to substance use may actually be caused by social determinants of health, or issues around acquisition and administration, not the substances themselves. For example, many people identified by healthcare, law enforcement, and child welfare systems as affected by substance use, have also experienced poverty, trauma, and systemic oppression. Because of this and other factors, high quality research that controls for all variables is difficult, if not impossible to find.

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CAUTION: Editorials and Opinions are NOT Evidence

While it can be helpful to hear experts' opinions, those experts should be prepared to back up their opinions with facts. It's ok to ask people to show you their evidence. A good provider will be happy to share the research with you.

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You've probably heard of "evidence-based medicine". It's the idea that we practice based on research and data. There's another way of practicing called "eminence-based medicine". It's the idea that we listen to the person who's been around the longest or who has somehow managed to be labelled the expert.
It used to be that such a person would periodically get to write a review article in some journal, and that would be how everyone learned what to do in medicine. That's a problem. We've got a solution. Systematic reviews!

Last week we discussed systematic reviews, and why they're better than review articles, or opinions. But they're not the only types of "studies of studies" I've presented to you. Sometimes you can go a step further. After you've collected all the appropriate studies, you can merge the data together and do one large analysis. Those studies are called meta-analyses, and they're the subject of today's Healthcare Triage

Putting Evidence into Action

Drinking during pregnancy is roundly frowned upon, for good reason. It's a huge risk factor for lots of post-natal problems. But prevention can be counter intuitive. Strong prohibitions and punitive measures for pregnant women who drink mostly just have the effect of driving women away from prenatal care. We look at the literature.


Cochrane Library "Cochrane summarizes the findings so people making important decisions – you, your doctor, the people who write medical guidelines – can use unbiased information to make difficult choices without having to first read every study out there..."

MotherToBaby "MotherToBaby, a service of the non-profit Organization of Teratology Information Specialists, is dedicated to providing evidence-based information to mothers, health care professionals, and the general public about medications and other exposures during pregnancy and while breastfeeding. Talk directly to the experts behind the most up-to-date research!" Call 866-626-6847 or text 855-999-3525

Drugs and Lactation Database (LactMed) The LactMed® database contains information on drugs and other chemicals to which breastfeeding mothers may be exposed. It includes information on the levels of such substances in breast milk and infant blood, and the possible adverse effects in the nursing infant. Suggested therapeutic alternatives to those drugs are provided, where appropriate. All data are derived from the scientific literature and fully referenced. A peer review panel reviews the data to assure scientific validity and currency.

UpToDate UpToDate® is a subscription-based resource designed to provide physicians access to current clinical information. It addresses specific clinical issues in the form of topic reviews.  According to UpToDate,  it “is designed to get physicians the concise, practical answers they need when they need them most—at the point of care.” Topic reviews are written by physician experts who review the literature then synthesize the information into specific recommendations for diagnosis, management, and therapy.

UpToDate® also provides patient education materials and information. Topics cover the most common medical conditions and procedures and provide information that can answer basic medical questions, helping patients make informed decisions.

  • The Basics: These topics are 1-3 pages in length and are written in simple language. They answer the four or five most important questions a person might have about a medical problem. The Basics topics are best for readers who want a general overview.

  • Beyond the Basics: These topics are 5-10 pages long and are more detailed. Beyond the Basics topics are best for readers who want a lot of information and are comfortable with some technical medical terms.

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