A new Canada-wide scientific assessment has found that alcohol causes more harm overall than any other drug in the country—ranking far above tobacco, opioids, cocaine, methamphetamine and cannabis.
Led by researchers at the Centre for Addiction and Mental Health (CAMH), in collaboration with national and international experts and published in the Journal of Psychopharmacology, the study used multi-criteria decision analysis (MCDA) to compare 16 of the most harmful and commonly used psychoactive substances in Canada across 16 types of harm. These included short- and long-term physical, mental and social harms to people who use drugs (e.g. loss of life, damage to physical health), and harms to others (e.g. environmental damage, economic costs), among other factors.
MCDA tackles complex questions where no single measure captures the full picture. Rather than focusing on a single outcome, such as deaths or addiction, this approach brings together multiple forms of harm, from health effects to social and community impacts, and weights their relative importance.
As part of the study, a national panel of 20 experts from six provinces took part in a two-day decision conference. The panel first scored each drug on a scale from 0 to 100 for each of the 16 types of harm, then weighted the relative importance of each type of harm. The panel then combined these scores to produce an overall harm score for each substance, showing which drugs cause the greatest total harm in Canada.
“This is the first time this approach has been used to assess drug harms in Canada, and it gives us a much more complete picture than we had before,” said JF Crépault, senior policy advisor and lead author of the study. “When we look at harm to people who use drugs and harm to others together, alcohol clearly stands out. Our findings highlight a major gap between the harms linked to alcohol and the way it is currently regulated in Canada.”
Alcohol, tobacco and non-prescription opioids most harmful
The analysis found that alcohol had the highest overall harm score, at 79 out of 100, followed by:
- Tobacco (45)
- Non-prescription opioids (33)
- Cocaine (19)
- Methamphetamine (19)
- Cannabis (15)
These scores represent population-level harm, not how dangerous a drug might be for any one person. They reflect both how risky a substance is and how widely people use it, capturing its overall impact on people and society.
The finding that alcohol causes the most harm aligns with results from previous MCDA studies in the United Kingdom, the European Union, Australia and New Zealand.
“Some substances, including opioids, cocaine, and methamphetamine, rank very high even though far fewer people use them, because the harms are so severe,” said Dr. Jürgen Rehm, senior author of the study, and senior scientist at the Institute for Mental Health Policy Research. “Alcohol combines serious harms with very widespread use, which is why it causes the greatest total harm in Canada.”
Why policy matters
The findings point to a clear need for drug policy that is informed by the real scale of harm in Canada. For alcohol in particular, the researchers point to proven, evidence-based measures such as controlling price, limiting availability, and restricting marketing and promotion as effective ways to reduce harm. More broadly, they emphasize that policymakers should reflect on the harms caused by substances as well as those caused by the laws and regulations that govern them.
“The key message here is that harm is not just about what a drug does to the body,” said Crépault. “How a drug is regulated shapes who uses it, how it is used, and how much harm it causes. Evidence-based policy can significantly reduce harm, and governments have a real opportunity to use regulation to protect public health.”