cartoon introduction to evidence in medicine

Anecdotes and Evidence: What’s the Difference?

• An anecdote is a personal story

What is an anecdote anyways?

I used to have a lot of back pain, but since I started taking

that remedy its been better

• Why aren’t stories good evidence?

Sample Size: One story doesn’t tell you everything

Anecdotes aren’t Evidence

What you don’t know is…… I would have gotten better on my own

…I still have pain, but I feel better because I believe the remedy worked

… that the other 99 people who took it didn’t get better at all

• Why aren’t stories good evidence?– Reporting Bias: people tend to report positive effects. – How many times have you heard this?

Anecdotes aren’t Evidence

I want to tell you about this home remedy I took that didn’t work at

all!!!

Hmm not many…

• Why aren’t stories good evidence?– No Control Group: people can feel better if they

expect that something is going to make them better

Anecdotes aren’t Evidence

Guys! I took this sugar pill and it made my back pain go away!

• One group of people gets the remedy and the Control Group gets a “sugar pill”, but they don’t know which one they got

What is Good Evidence then?

I wonder which one I got…

REMEDY SUGAR PILL

• Having a large Sample Size: The more people that you have the better the evidence that the remedy actually works

What is Good Evidence then?

REMEDY SUGAR PILLHe might have gotten better on

his own, but would all these

people have gotten better?

• Lots of independent experiments that show the same result

What is Good Evidence then?

Hmmm this experiment shows

it works, but there’s 19 experiments

showing it doesn’t work…

STUDY #1: With Big Sample Sizes, The

Remedy has an Effect

STUDY #2: With Big Sample Sizes, The

Remedy has no Effect

Sample Size and Error

Big Sample

Size

Small Sample

Size

Big Sample

Size

Small Sample

Size- 0 + - 0 +

Sample Size and Error

Effect of smoking on having a premature baby

1Shah, N and MB Bracken. 2001. A systematic review and meta-analysis of prospective studies on the association between maternal cigarette smoking and preterm delivery. Journal of Nutrition. 2001;131:1032S-1040S.

Effect of acupuncture on treating stroke

2Tang J-L, Zhan S-Y, Ernst E. 1999. Review of randomised controlled trials of traditional Chinese medicine. British Medical Journal 319:160-161. .

Decreased Risk Increased Risk Negative Effect Positive Effect

The Placebo Effect

What is a Placebo?

• A “sugar pill”: Made of something that doesn’t affect the body, like water or sugar. It is used to test if a remedy works better than giving “nothing”.

I wonder which one I got…

REMEDY SUGAR PILL

What is the Placebo Effect?

When people take the sugar pill, they expect that they will feel better and they often DO feel better: this is the Placebo Effect

SUGAR PILL

Pills are Medicine.I FEEL BETTER!!!!!!

Placebo Effect Examples

• Your parents giving you chicken soup when you have a cold

• You give a child a kiss on their wound to make it feel better

I feel better :)

I like feeling better….What’s the harm?

• A remedy that causes a placebo effect doesn’t actually make you better, though you might feel better

• If you have a serious disease (like cancer) you might delay getting treatments and your disease could get worse

• Costs money! $$$$

Herbs versus Drugs

• Herbs are drugs!

Herbs are Drugs!

What?!!!!! No way….

Drugs?…

What is a Drug, Anyway?

What is a Drug, Anyway?

• A drug is a substance that brings about a biological change in our body

Plants are Chemicals that can have effects on your body!

Many of our Pharmaceuticals came from Plants

FoxgloveDigoxin

Willow Bark Aspirin

Pharmaceuticals

Known drug Known effect Known Amount

Herbal Remedies

What’s the Drug? Effect?? Amount???

• Herbal remedies can have side effects

• They can also interact with your other medications

• So when your doctor asks you what medications you are taking, you should tell him/her about the herbal remedies you are taking too!

Herbal Remedies have Side Effects too