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How do health experts reach scientific consensus?

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How do health experts reach scientific consensus?
Get Real! articles are developed through a collaboration between Healthcare For Real and MediaSmarts.

Making decisions about your health can be difficult. Your family doctor or a medical expert is a good source to turn to, but even the experts don’t always agree. When evaluating a health issue, it’s important to understand the scientific consensus on the topic.

What is scientific consensus?

By its nature, science is always changing and evolving. Scientific consensus isn’t just what most scientists believe: it's what the weight of evidence in a field suggests is most likely true. There can be consensus on a fact or on a theory (an explanation of how something works or why something happens).

There isn’t a consensus on every topic. Questions like what causes Alzheimer’s disease or the best way to treat injuries to the Achilles tendon are still in flux.

It’s often easier to reach a negative consensus: Scientists don’t know exactly what combination of factors causes autism, for example, but vaccines have been fully ruled out by comparing children who received vaccinations with those who didn’t to see if they were more likely to develop autism. (They were not.)

How is scientific consensus reached?

Scientific consensus is achieved through a rigorous process. It starts with a question and a hypothesis, followed by an examination of the evidence. If the results are credible, they are published. Other scientists then replicate this analysis, either confirming, expanding or challenging the findings.

The scientific consensus can change when there is enough strong evidence, but that doesn’t mean things like medical advice just change at random. It takes multiple studies from reliable experts for this change to happen. To put any claim in context, we need to know if there is a consensus on the topic and, if there is, how strongly it is held.

Dive deeper: Why does health advice change?

People who push misinformation may use different tactics, like cherry-picking the few pieces of opposing evidence, to undermine the consensus. It’s important to be aware of these tactics when you see claims that go against the scientific consensus.

Why is scientific consensus important?

Scientific consensus ensures that our understanding of the world is based on robust, tested and widely accepted evidence, which is essential for progress and informed decision-making. Public health authorities draw on scientific consensus to make decisions about how to prevent people from getting sick and how to treat diseases.

How can I go about finding out what the consensus is on a health topic?

Look for position statements from authoritative sources like the Canadian Encyclopedia, Health Canada, the Public Health Agency of Canada, the National Academies of Sciences, Engineering, and Medicine, Cochrane or professional organizations like the Canadian Paediatric Society.

Frequently, the easiest way to do a search of these sources is by using a "site: query", which allows you to request search results from one particular website. To do this, type the words “site:cps.ca” into Google along with the words you want to search, for example “Social media.”

This is what the search would look like if you wanted to find out if the Canadian Paediatric Society and the National Academies Press have released position statements on the possible effects of social media on youth:

“social media” “youth” site:nap.nationalacademies.org

“social media” “youth” site:cps.ca

Both searches lead to position statements that provide an overview of current research on the topic, including to what extent there is a consensus. (You can search the Canadian Medical Association website the same way!)

It’s important to remember, though, that any organization can claim to be authoritative or to represent professionals in a field. As with any source, do a search to make sure that an organization or institution is reliable and authoritative before consulting them.

Where’d we get this information?

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How do I know if someone is a reliable health expert?

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How do I decide if I can trust the health information I’m seeing?

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What should I do if I see someone sharing health misinformation on social?

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