How to read and understand cannabis science

By Richard Shrubb

NORML recently posted a link to a blog on Facebook. The blog in question suggested that cannabis can be beneficial to bipolar disorder. On one line of thinking this is very interesting – cannabis is a nice sedative, and I have seen studies that show it can actually be good at treating psychosis. This fed my interest.

One of my specialisms is as a medical science journalist, so I looked at the study myself. What came up led to a bit of a dingdong on the Facebook page, because the bloggers writing the piece overlooked a key part of the study – that the group who used cannabis had a far higher prevalence of psychosis than the non using group. In short, yes it does have some favourable results in treating bipolar disorder, but there is a high risk of psychosis.

ArohasilhouettesReading science is key for a movement that has science used against it so rabidly and effectively. The Mail raves incontinently seemingly every week about cannabis “causing schizophrenia”, which when you speak to the scientists that the Mail quote, you tend to find is nothing short of bollocks. Scientists working in that field who are unfortunate favourites of the right wing press live in fear of headlines taking some half truth from their studies and blowing it into supposed fact.

I have paranoid schizophrenia. I was led to believe it was caused by smoking weed. Only through my journalism did I learn that people with psychosis shouldn’t touch it, and if you even get paranoid smoking it, you should leave it alone. I also learned that there is little to fear in most people having the odd joint. More to the point, cannabis does NOT cause schizophrenia.

In order to respond effectively to broadsides from the Mail and selective use of science from MP’s, people need to understand how to read science and thus to respond effectively. I work closely with leading science journalist Dr Toby Murcott. He has kindly responded to some basic questions about “reading science”.

For all we know, then Prime Minister Gordon Brown was talking to his Dad’s boss (God) when he had the revelation that cannabis causes schizophrenia – no scientist would ever say that! According to Dr Murcott, science “has important limits. Firstly, science cannot prove something, it can only disprove. This means that you cannot say to science “prove to me that (insert your own pet theory here)”, which is what many politicians would like.”

Science can never prove. As Dr Murcott says, “Einstein’s Theories of Relativity are still being tested to this day, even though they have survived every attempt to knock them over so far. Any scientist who succeeds in finding a chink in its armour will be praised and may well win a Nobel Prize.“ What we accept as “incontrovertible proof” from the best physicist of the last century, may well be disproved in our lifetime!

Moving back to the world of weed, there is a lot of anecdote that cannabis can wipe out cancer tumours. Many people say this is incontrovertible. I understand that there is a group of scientists taking this anecdote and trying to show it scientifically. Just because you “know” it to be true, unless scientists test your ideas there will be no way you will get a THC spray for your lung cancer any time soon. People who believe strongly enough that weed can cure their lung cancer may actually recover. There is a massive amount of work being done on so called “placebo”, an inert chemical that is taken in the sincere belief it is a wonder cure, and the body fixes the problem purely on the belief it is true. Until I read something that said it takes 20 minutes to get your fix from an e-cigarette I believed I was getting the hit instantly. Reading that text destroyed my belief and now I don’t get a hit from e-cigarettes. That bloody research may have shortened my life by a decade.

Dr Murcott explains the difference between anecdote and research, “imagine you know nothing about astronomy and you sit in a field from sunrise to sunset. If you were asked whether the Sun goes around the Earth or the Earth around the Sun, the evidence of your eyes will clearly tell you that the Sun goes around the Earth.” Science however has shown us that the earth spins and travels around the Sun, providing day, night and seasons.

Generally in medical research the bigger the number of participants – the “cohort” – the better the piece. Dr Murcott says, “the crude rule of thumb is the more patients the drug or treatment is tested on, the more reliable the results are likely to be.”

The Burning Question

So, if everyone in the UK participated in a cannabis and schizophrenia study – say 60 million people – you would find that 1% get schizophrenia. This is core to my understanding of the links between cannabis and schizophrenia. Since the 1960’s several tens of millions of people have abused psychedelics yet the rate of schizophrenia hasn’t even wobbled globally. I’m sure if everyone in the UK got stoned for a month in a badly made study, the Mail would point to the 1% and say “cannabis causes schizophrenia in 1%”! This is why scientific research has to be designed properly. Likely you’d have three groups of 20 million – one group of stoners, another smoking THC free hemp, and the third smoking nothing at all. You would compare the rates of mental illness among all three groups and could draw your conclusions.

Why does medical research take so long? It seems frustrating. But if you gave out a drug that yes, wiped out a lung tumour but drove everyone who took it so nuts they jumped off Beachy Head, you wouldn’t be saving lives. I’ve taken a drug that helped stop my alcoholism but it made me psychotic for five years. I’m lucky to have a career, let alone a life.

Research goes through three phases over around a decade if all goes well. Most drugs fail in testing. Dr Murcott explains the three phases:

Phase One. This is the first time a drug has been tried in humans and the purpose is to ensure that it is safe.”

Phase Two. This is the first time the drug will have been tried in human patients who have the condition it is designed to treat. A group of suitable patients will be selected and then divided at random into two or more groups. One group will get the experimental drug, and the other groups may get an established treatment or a placebo depending on the design of the trial. Normally the drug will have to show it is both more effective than a placebo and the current treatments before moving to Phase Three.”

He continues, “Phase Three. This is the real crunch. Depending on the drug and the condition the drug will be tested on large numbers of patients, often many thousands. This is point at which the drug has to show it offers real improvements over current treatments both in terms of safety and efficacy against the condition it’s designed to treat.”

Phase Three is at a very large scale. The antipsychotic I take has a 50% increase in chance of the patient becoming obese. It also has a 3% rate of diabetes – above the normal rate of 2% in ordinary people. The authorities will weigh up the risks of diabetes against the benefit of the drug. I’ve made the choice to try to live a lifestyle that reduces the risks of diabetes but am happy that the drug doesn’t make me twitch uncontrollably or sedate me so much I am a bloody zombie like the drugs of the 1970’s did. Because I am not a twitching zombie I can function in society – exactly what the drug was designed to do. The risks weighed up? Olanzipine got through Phase Three trials and was licensed.

In another interview, Dr Murcott told me “science is about being nosy”. All scientists do is test something to destruction. Unfortunately different designs and motivations behind research find different things. At the moment with regard research on cannabis you can do as one MP did recently on the request of NORML and be selective as to which research you read and choose to believe.

Because science is inexact in regards cannabis, people can believe what they want to and generally come up with the research to prove their own beliefs. Yes cannabis can cause psychosis. It only causes psychosis in a certain group of people and no one understands why Chris can smoke bath bongs all day and be OK where Peter loses it on one toke of a spliff. Until someone designs a study that explains this, which can be repeated at a large scale a dozen times, it is for those to choose their beliefs. At the minute, the Daily Mail (readership, 3 million) has a delusion it seeks to prove every day (like I do my psychotic delusion) and MP’s read it as well as the poor souls who waste their money at the newsagents. Until something utterly incontrovertible comes?  Learn to read science well, and derive your own opinions!

Richard Shrubb

Richard Shrubb

Richard Shrubb is a freelance journalist with a specific interest in medical science and sailing, for more info about Richard, see his web site and you can follow Richard on Twitter #Shrubberz


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  1. i think it will be the same for any drug it depends on the person,i have ms and have been smoking it for 22years and have no problem with it and it helps me with the pain and relax’s me but i know other ms sufferers that cannot have it as it doesnt agree with them.same with alchohol i am t-total as the drink does not agree with me,my friend collapsed last week,turns out he is allergic to codiene(prescribed),so it doesnt really matter what tests are done it all boils down to wether your body and mind can cope!luckily i can!

  2. I really dont believe cannabis causes psychosis. It may cause short term psychotic behaviour in the user that isnt familiar with cannabis effects but long term psychosis? no way.

    Its way beyond my comprehension why these studies dont include the effects of western culture, the only thing that gives me psychosis concerning cannabis is the constant stream of utter bullshit the gov and media spin about this herb.

    Cannabis like most drugs mirrors yourself, to say cannabis causes psychosis is foolish, it reveals to the user that they may have psychosis or psychosis type tendencies. Please dont buy into this hype about psychosis and cannabis before you take a look into western cultural pressures and transference.

    Western Culture is the problem here, not cannabis. I can say that with just as much conviction and authority as the original blog post.

  3. I will say it can purly becuase im a mental health patient any drug that effects anandamide regulation leads to problems in the organ. when it comes to signaling anandamides role in emotional memory formation is hampered by thc no way around this. now here comes the issues a memory is formed after around 15 firings of the new connection. THC being bioactivly stronger than AEA and sitting above the FAAH layers speeds up this prossess of memory formation. What we have yet to understand about the other componant of this prossess 2AG/2AG-3p (CBD) is how it works alongside or inbetween the AEA open and close signals. spinal tests on psychotic patients revile they have up to 9 times the amount of AEA but normal 2AG/-3p. My current understanding of these prosses lead me to belive that AEA acts as a data register donating were one instruction begins and another ends with the 2 typese of 2AG making the main body of data. If like all other computer systems the operating core is flooded with empty packets of data then its going to malfunction if its flooded with just the headers then its going to get very confused and will try to find the next bit of chemical data to try and complete the instruction to the cell.

  4. If cannabis fell inline with the likes of other drugs used in western culture that provide productivity like sugar, coffee, nicotine etc etc would there be this research?
    Cannabis has been legal for a lot long than it has been illegal but for some reason only now is science finding these things. It all wreaks of cultural control to me.

  5. Smoking cannabis can trigger a psychotic episode in people who have psychotic disorders. It’s a well recorded issue and should be respected. It does not cause an otherwise healthy person to acquire a psychotic disorder, but it can be quite devastating to some (clearly not all) people coping with certain kinds of mental illness. These individuals should not take cannabis, unless they know firmly from experience that it doesn’t have this effect on them. Anyone who’s ever consumed more cannabis than they were comfortable with can probably empathise with what that state might do to someone who is already prone to breaks with reality. For someone who is struggling to cope or still working out their medications, using cannabis and having a bad reaction could be incredibly destablizing.

    Prohibition certainly isn’t stopping people who shouldn’t consume cannabis from getting their hands on it, so it’s not an argument against reform. Many people also can’t or shouldn’t consume alcohol because it triggers aggression or depressive disorders. It doesn’t cause these disorders, but it may trigger a very unpleasant or dangerous episode. Unfortunately we’ve got prohibition-licensed ignorance combining with a cynicism about mental illness to prevent an honest discussion of the benefits and incredibly low risks of cannabis use. I know plenty of people who can’t use cannabis, either because they find it unpleasant or because it triggers their symptoms, and none of them oppose decriminalisation or legalisation. So it doesn’t hurt us to be honest and straightforward about cannabis and psychosis.

  6. A question:
    So if high THC content cannabis is “likely” to cause psychosis then could someone please clarify why the demand for high THC cannabis has risen in the past 20 years? IS this a cultural response or just purley a chemical demand?

  7. so why does alcohol cause all that??? oh thats right it disolves via nurosteroids CBreceptors it blocks and califies nuronal cells. Alcohol aquired mental illness is also passed on damage to the ECSN cant be reversed.. seems folks need to get clued up on drugs here.

    Common Man the problem is its all only just being reviled to us we have only just aquired methord to look beyond the receptor to look inside it to mesure how it changes with different endocannabinoids and endovaniloids….

  8. I agree to a point John Ellis but surely even without the science, wouldn’t it become highly apparent that cannabis causes problems a looong time before now? What of past cultures not in western civilization where cannabis is accepted wholly? Do they have the same apparent sociological problems allegedly caused by cannabis?

  9. oh that was a feild test. high thc… there are heratige plants that have been out of use for over 100 years that have no cbd and 25% thc. what has gone on in the last few years has mearly been stabilisation of medical strains through manipulation of loci. the rise in thc wasn’t realy about the THC end product but its precursors THCv THCa CBDa CBDv these operate in the FAAH layers and the FLAT inercell tranceport without the high.. Get the plants to produce huge quantities of this and your sorted cure most illness or at least correct its functioning. problem is oxygen and carbon soon convert these to CBD and THC… hence why we have lots of high strenght herb.. but what are the actual THC values in the plants.. how are they broken down? what is the percentage of THCa of THCv both none psycotropic.

  10. yes they do or at least they have the same suceptabilities to high THC, culturaly folks used cannabis on a 4 to 0.5 ratio So if the kush is 20% thc with 4 % cbd you get a 5 to 1 ratio. that all changed in 1970 somthing with the advent of skunk No1 THC levels droped cbd levels droped and yeild went through the roof. taken a long time to get cannabis back to were it was i use a 4 to 1 ratio for mental health the closer i move away from that the quicker I slide down hill Im early onset through fetal alcohol disorder. got visitors back later but top nuroscientists agree with me ..

  11. Skunk is just a generic name for an old Sensi Seed strain of cannabis. As the article states, cannabis does NOT cause schizophrenia.

    It is true CBD is an anti-psychotic, which is formed at the later stages of budding, therefore weed that is often harvested too early on the criminal black market may have a lower CBD content, so that is a product of prohibition.

  12. Chris Bovey so you think that its a case of the criminal market wanting to knockout their product faster ergo higher thc content is nothing to do with getting a greater “stone” ( or w/e you wish to call it) but purely a result of a faster monetary turn over? interesting.

  13. Well I don’t think it’s a case of the criminal market deliberately setting out to do this, but of course, if weed is harvested earlier, probably for 2 reasons, – 1 greed in that they want quick turnover of profit & 2 – they want to get the stuff out as fast as possible to reduce risks of being caught.

    I should also say it is a bit of a myth all the cannabis on the market now is super strength, lol, I wish 🙂

    The answer is end prohibition, so you know what you are getting. For medicinal users, this is very important, as their are so many different strains for different conditions, and also for time of the day, for example, in the morning a MS patient might want a nice uplifting sativa for energy, whereas at night, a strong indica to help get a good nights sleep.

  14. “I should also say it is a bit of a myth all the cannabis on the market now is super strength, lol, I wish :-)”

    Yeh i really dont know where they get this wrped propaganda from tbh i remember weed in the early 80’s before the even of “skunk” flooding the market. When you could still get red leb, gold seal, thai sticks and Nigerian sensi, im not sure wether its my tolerance levels but i clearly remember all this stuff to be waaaaaaaaaaay more potent than the stuff we get today.

  15. I don’t see how they can say that the weed today is much stronger than it was 20 years ago, comprehensive tests on THC content did not start until 2000. Besides, maybe the weed was weaker but nobody smoked it, the fashion in those days was for Hash. Some strains of this were just as strong as the weed we have now. I blame Howard Marks for this, the Welsh git. As for psychosis, yes it does cause this but it is very rare indeed. It happens in 13-16 year old with a propensity for psychosis who smoke it 24/7/365. Stop smoking it and the symptoms go of their own accord, but they will have to give it up for about 2-3 years in order not to have a relapse.

  16. @Tim Woodman Do you have any research to back that up Tim? not been funny just would like to see it for myself. In teens i would say it is a risk as been a teen you are been constantly assaulted by your own body chemistry post puberty. Teens have always been troubled because of this, maybe cannabis was just making them more aware of this? After all in my lengthy experience with cannabis it ony enhances what you feel, maybe thats just me
    /me shrugs

  17. If they say that that stoners have increased susceptibility to madness, how do they not know that it is not the other way around? They like to say that it causes 40% of those who take it to go mad, but the case is that 40% of the mentally ill smoke the stuff as it helps them.

  18. I really do no think weed is much stronger than it was 20 years ago, this is mainly nonsense spouted by politicians who were smoking weed at university 20 years ago and want to try to somehow justify it by conning people they were smoking some harmless herb, as opposed to the imaginary “deadly super strength skunk” of today.

    For sure there are strong strains around and for reasons we mentioned earlier, they are some lower CBD ratios due to early harvesting; however generally the notion cannabis sold on the streets of Britain is much stronger than the cannabis Jacqui Smith was smoking when she was at uni, is simply untrue.

    @Common Man I’d agree teens shouldn’t be smoking cannabis the same as they shouldn’t be getting pissed on booze; interestingly in The Netherlands they have lower usage of cannabis amongst minors, precisely because cannabis is sold in a regulated market via the coffeeshops who are subject to strict sanctions if they are ever caught selling to under 18s. In fact so strict, they just don’t do it, as first time it’s a big fine and second time they close you down.

  19. Im somewhat confused by a lot of those articles John Ellis, Scientists say they can measure all sorts of chemical reactions involving receptors and the chemical reactions that go on in the brain but can they really measure an accurate emotional response based on this? let alone wether or not they can predict from person to person their brain chemistry in relation to a persons emotional well being and psychological action/reaction circumstances.

    I dunno maybe im in denial about science but i don’t honestly believe at the end of the day they have an accurate clue about what they are trying to do in such standardised testing when most peoples circumstances and reactions to them are extremely different.
    I will concede that some standardised testing is whats needed but to draw definate blanketing conclusions wreaks of standardising the human to a point of been just a biological machine with predictable psychological response mechanisms. It just doesnt ring true for me.

    Im a fan of occams razor when it comes to the cloudy murky world of science.

  20. Some people put way too much faith in the so called ‘medical system’ in the first place. They are the frontmen for the pharmacuetical companies who push drugs that kill people while they collect profits.

    Wait for the ‘medical community’ to prove that cannabis is a healing herb and literally thousands and thousands of more people will needlessly die.

    Before profit became the main motivating factor in the ‘health care’ systems, cannanis had its rightful place at the head of all medical treatments.

    • In order for “thousands and thousands to …die” there would need to be convincing evidence that cannabis treated a number of otherwise fatal diseases. Can you name any ? In fact one would do? Where there is any proof – that doesnt involve Youtube?

      “But there’s no role, or hardly any role, for smoked cannabis in the treatment of chronic pain. There are safer alternatives, such as cannabis in pill form or inhalers. There are toxins in cannabis smoke that are carcinogens, and that accelerate heart disease. Smoked cannabis is addicting, unsafe during pregnancy and especially dangerous for young people, in terms of triggering psychosis, depression and mood disorders.”

      Dr. Meldon Kahan, medical director of the Substance Use Service at Women’s College Hospital in Toronto

  21. Pingback: Cancer Cured By Cannabis - GoHealthy

  22. They don’t want us to have medical cannabis because you aren’t supposed to enjoy medicine are you..
    Makes me mad, cannabis works for me.
    My docs refuse to give me anything to sleep for years because I used to use hard drugs and it’s on record so he probably thinks I want to get stoned before I sleep..
    I am sleeping better than I have done for years now..less anxiety attacks too..
    I wonder why??

  23. This article lacks science.
    The procedure a company has to take to get a medicine through is not relevant to a patient, or even in the patients best interest. It is a procedure that arises for purely commercial reasons. We have the right to health, we do not need a study to tell us it works, it is just helpful that they are now coming thick and fast.

    • This is about the most stupid statement I have ever read.How can you possibly say it lacks science and then claim that anything should be used without any evidence? It has nothing to do with commercial interest – it is simply if you give something to a person it is beyond all reasonable doubt that you want it to have the effect that it should have rather than kills or harms you. Surely this isnt too difficult a concept to grasp?

  24. Hello Michael Murray,
    I said this article lacks the science, maybe you would be so kind as to point out where it is?
    I would be more than happy to actually talk about the science of cannabis if you want?
    If you think people regularly give things away, then so be it. In my experience most people only give something when they receive something of equal value in return. Of course you would want to know what you where being “sold” was not going to kill you. However if you are not giving/selling anything away it just would not be a concern to you. If you choose to consume something, you do not need a piece of paper saying it is safe. You have to understand, people willing consume harmful things, just look at alcohol and tobacco.

  25. I have smoked cannabis for 20+ years and there is a constant trend in my family tree of mental illness, fortunately I have not as so far been diagnosed with any such disorder. My father however suffers with Bi Polar and has been on medication for the last 15 years. Last year he attempted to come off his medication, as he said it was making him feel dead inside. As with many people who take medication on a daily basis for their mental health he wanted to try life without it. It did not go well for him and he was soon back on his medication and feeling as he was before. I plucked up the courage tell him that I indulged in the art of marijuana and asked him if he would like to try some as I thought that this may help along side his prescribed medication, to my surprise he said that he would be willing to give it a try. He is a very serious person at he best of times so I knew that he would be responsible when using the herb. Guess what?? … It helps him, it makes him feel NORML, its not a cure and as I have said he still takes his medication daily but he no longer feels dead inside. I am happy that he is happier. Thank you Mary Jane.

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