One of the researchers was funded by the Medical Research Council. The study was published in the peer-reviewed journal Drug Test Analysis.
Researchers contacted 5 police forces which had been involved in previous surveys of cannabis, in 2005 and 2008. The forces were asked to send all seized cannabis samples in their property stores for analysis.
To see whether the time the sample had been held by the police affected the strength, they measured 34 samples where the length of storage was known, and looked at whether CBN levels were linked to time stored.
- damage your lungs
- increase your risk of road accidents
- damage your fertility and, if smoked when pregnant, damage the unborn baby
It’s concerning that this study suggests sinsemilla is becoming much more common, and that where resin is on sale, it has more THC and less CBD than a decade ago. People who base their ideas about cannabis on the drug they smoked many years ago may not realise the strength and potential harm of the cannabis sold on the street today.
Only 1 of the sinsemilla samples contained CBD, the protective agent. While most resin samples did contain CBD, researchers found the average level had dropped from 4.3% in 2005 to 2.3% in 2015/6.
- It only looked at drugs seized by police. It’s possible that police may prioritise arresting and confiscating drugs from people selling sinsemilla, because of its perceived harm. This might mean the proportion of cannabis resin in the study could be artificially low.
- It only analysed a proportion of the samples of sinsemilla, and only 250mg from each sample. The overall sample strength might have varied, because the cannabis plant’s concentration of THC varies in different parts.
- Only 5 police forces were involved, so we don’t know if the results would apply equally around the country.
This matters, because doctors think people who use cannabis with high levels of THC, especially without CBD to counteract it, are more likely to become addicted and develop mental health problems.
Cannabis doesn’t just affect mental health, smoking any form of cannabis can be bad for your health in other ways.
'Almost all cannabis seized by police now comprises high-strength varieties, with outdoor-grown herbal strains and hashish barely found' The Guardian reports