It is now quite widely known that cannabis use is linked to a small but significant increase in the chance of developing psychosis, but it is less widely known that one of the ingredients in cannabis actually has antipsychotic effects.
Unlike THC, it’s lesser known cousin cannabidiol is not responsible for the cannabis ‘high’ but it is naturally present in the plant.
There is accumulating evidence that cannabidiol has an antipsychotic effect, potentially damping down the psychosis-promoting effects of THC.
The amount of this substance varies in street cannabis, with some strains having more cannabidiol than others, and ‘skunk’ having the least of all – it being mostly eliminated by selective breeding for high THC content.
An ingenious new study looked at levels of cannabidiol consumption in groups of cannabis smokers by testing hair samples, and found that the groups who had the lowest cannabidiol levels had the most psychosis-like experiences.
In contrast, those with the most cannabidiol levels had the least psychosis-like experiences – equal to a comparison group with no detectable cannabis compounds who were presumably non-smokers.
One caveat is that the participants were all recruited from a study on ketamine users (a substance known to raise the risk of psychosis), so the study will have to be repeated on people who solely use cannabis to be sure the effect isn’t a specific interaction between the two drugs.
However, the results seem to tie up with what we already know about how THC and cannabidiol work, so may reflect a genuine effect.
As any visitor to Amsterdam will tell you, cannabis breeders often try to maximise THC content to grow a plant with more ‘bang for the gram’.
As cannabidiol seems to have no effect on the high itself, perhaps we might see breeders also trying to maximise the cannabidiol content in future, potentially reducing the risk to smokers’ mental health.
UPDATE: A reader who prefers to remain anonymous sent in the following interesting comment:
Cannabidiol is in fact bred for in cannabis product, but is mainly done for taste. There are mentions within the cannabis breeding literature (i.e. seed catalogues) on breeds which lack psychosis (often defined as “low paranoid strains”), and these correspond to the “tasty” breeds to a great extent.
Probably ‘lacking psychosis’ would be considered controversial by the scientific community, but it’s interesting that the growing and smoking community make the distinction between high and low ‘paranoid strains’. It’d be interested to see whether these stand up to scientific investigation.
Link to abstract of scientific study.
Mind Hacks 
I wonder if the scientific community has done any investigation as to the chances of developing psychosis after getting arrested for marijuana?
G-man makes a good point. I’ve always wondered how much of the “pot makes you paranoid” can be linked to 70 years of being told that one puff will drive you mad, lead to heroin, and cost your freedom. If you’ve been told smoking pot is the gateway to hell, you’d certainly be nervous about it the first time you opened the gate.