Cannabis Resin Is Now 25% More Potent Than It Used To Be, Study Finds

by : Emily Brown on : 15 Nov 2020 11:51
Cannabis Resin Is Now 25% More Potent Than It Used To Be, Study FindsPA Images

A global study has found that cannabis resin is 25% more potent now than it was 50 years ago. 

I’m sure we’ve all heard elderly relatives talk about how ‘it wasn’t like this back in my day’, and if you happen to be having a conversation about hash, then they’d be right.


Researchers with the Addiction and Mental Health Group at the University of Bath based their findings on data from more than 80,000 cannabis street samples tested in the past 50 years in the US, UK, Netherlands, France, Denmark, Italy and New Zealand.


The team studied both herbal cannabis and cannabis resin to investigate changes in concentrations of THC – the intoxicating component of cannabis responsible for giving users a ‘high’.

Concentrations in both forms have increased over time, with lead author Dr Tom Freeman explaining that the changes in strength are so dramatic that cannabis now ‘differs enormously from the type of drug used by people 50 years ago’, The Guardian reports.


The increase was most dramatic in cannabis resin, where researchers found THC concentrations have risen 24% between 1975 and 2017.

In herbal cannabis, THC concentrations were found to have increased by 14% between 1970 and 2017. The researchers believe this is primarily due to a rising market share of stronger varieties, such as sinsemilla.

cannabisPA Images

Freeman noted that as well as changes in the makeup of the drug, attitudes towards cannabis have also shifted. He explained: ‘There is now a greater appreciation of its complex interplay with mental health and potential medicinal uses.’


Study co-author Sam Craft pointed out that cannabis resin is often seen as a ‘safer’ type of cannabis, but the findings show that it is actually the stronger option.

Craft continued:

Traditionally, cannabis resin contained much lower amounts of THC with equal quantities of CBD (cannabidiol, which is believed to have some health benefits), however CBD concentrations have remained stable as THC has risen substantially, meaning it is now much more harmful than it was years ago.

weedPA Images

In the study, published in the journal Addiction, the researchers argue that the increase in THC concentrations highlights the need for harm-reduction strategies regarding the drug. These could be similar to measures in place for alcohol, such as standard units and guidelines on consumption limits.

Freeman commented:

As the strength of cannabis has increased, so too has the number of people entering treatment for cannabis use problems. More Europeans are now entering drug treatment because of cannabis than heroin or cocaine.

Cannabis is the most widely used illicit drug in the world, though some countries and US states have now made it legal for both medicinal and recreational use.


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Emily Brown

Emily Brown first began delivering important news stories aged just 13, when she launched her career with a paper round. She graduated with a BA Hons in English Language in the Media from Lancaster University, and went on to become a freelance writer and blogger. Emily contributed to The Sunday Times Travel Magazine and Student Problems before becoming a journalist at UNILAD, where she works on breaking news as well as longer form features.

Topics: Health, Cannabis, Marijuana, Weed


The Guardian
  1. The Guardian

    Cannabis resin now 25% more potent, global study reveals