Cannabis Works Differently and Variably

Modern pharmacology is entirely based on the distilling of the active ingredients from plants to concentrate their efficacious effects into drugs, to relieve pain for example. But not all plants work by directly relieving pain. Cannabis is an enigmatic plant extract. It is a pain reliever, but it makes pain more tolerable, but does nothing physically to reduce it.

This is the main result from a research study, out of the University of Oxford in England. MRI scans of the brain activity of the experiment’s volunteer subjects, recorded a definite calming of the pain centers of the brain when patients used the drug. Cannabis is a ‘psycho-drug’ that appears to work on the emotional facets of pain. The level of effect of cannabis on pain was found to be extremely variable according to different participants. The results of the study were recently published in the Journal of ‘Pain’, appropriately enough.


The Oxford team co-opted 12 healthy males to participate in their research experiments. 6 subjects were randomly assigned to the group taking 15 milligram tablets of ‘delta-9- tetrahydrocannabinol’, or THC. This is the ‘magic mushroom’ active part of cannabis. The other 6 subjects were given a placebo. The volunteers were then subjected to limited amounts of pain via a paste containing chilli, massaged into a sensitive are on the leg. It caused burning sensations in every case. Again half the group had the genuine pain causing paste while half had an inert ‘dummy’ inducement.

MRI scanning was conducted 4 times and recorded how blood flows in the brain changed along with the subjects perceptions of pain. The scientists discovered that the subjects who had taken the THC tablet felt no difference in the level of burning sensation but definitely felt that the pain was lessened. The MRI scan captured this phenomenon as significantly reduced brain activity in the known ‘pain’ regions of the brain. The reported effects were supported by the physiological reactions. The key learning point from this study will be in diagnosing which patients could benefit most from cannabis derived pain relief medication, because reactions are variable among different types of patient.

The next step on this research trail is to find predictors for patients who will benefit from cannabis. This means a larger study with participants chosen because of their long standing chronic pain conditions. Cannabis is not like other more conventional pain relievers. Some patients find it very effective while others do not react at all. Or even in some cases react adversely to it. When compared on the MRI scans with say opium derived pain relief, there is little change in brain activity in the same areas of the brain. This indicates that cannabis is working on the emotional element of our experience of pain, and that the effects are extremely variable.

This study is one more piece of evidence in the growing consensus among researchers that cannabis seems to disengage the pain sufferer, from the pain, rather than relieve the symptoms themselves, as opiates do. This latest research was paid for by the UK Medical Research Council and the National Institute for Health Research.

Claire Al-Aufi

Claire Al-Aufi is a contributing author for Hive Health Media who provides updates on health and fitness news.

2 thoughts on “Cannabis Works Differently and Variably

  • February 4, 2013 at 9:42 am

    Many things have to be taken into consideration here. Firstly, the isolate THC is a pure form of the natural one in the entire plant product. Therefore it would be interesting to know the actual efficacy of the wild-type THC compared to this pure isolate. That would help in knowing whether there are other prodrugs in the wild type that might even be better than THC. Secondly, I believe that there was no bias in this study because if the Test Subjects were told what they had received their expectations could have beclouded the actual result that would have been obtained from the experiment. Thirdly, the subjects should have been their own control. I say this because even a normal sensation of pain is relative in individuals; the level of pain one feels from a particular stimulation could be different in another individual. However if each subject was his/her own control, then the true assessment of pain before and after administration of THC would have occurred. First, the subject would take the placebo and then subjected to pain sensation; after what could be a washout time, he/she would then take the THC and the pain sensation is administered again. And in each occasion he/she would be blinded.

  • January 31, 2013 at 3:41 pm

    You trying to say that cannabis causes brain shrink with that photo you used?


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