Home / The Science of Marijuana Sheds Light on a “Dark” Drug

The Science of Marijuana Sheds Light on a “Dark” Drug

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“Who is right?” asks Leslie L. Iversen, a professor in the Department of Clinical Pharmacology at Imperial College London School of Medicine and founder of Panos Therapeutics Ltd. “Is cannabis a relatively harmless ‘soft drug?’ Does it have genuine medical uses that cannot be fulfilled by other medicines? Or … is cannabis in fact an addictive narcotic drug that governments are right to protect the public from?” These questions are posed to the reader in the first chapter of his book The Science of Marijuana.

Although it was first released by Oxford University Press in 2000, The Science of Marijuana is still a knowledgeable and relatively up-to-date work that delves into the history, pharmacology, chemical composition and related compounds, the effects of and the societal attitude to the drug. Dr. Iversen describes himself as “a scientist who works on understanding how drugs act on the brain” and served as a consultant to the House of Lords Committee on cannabis, which declared, in 1998, that marijuana has both good and bad points. (How uncontroversial of them!)

One major, fascinating fact to be exposed early in the book (Chapter 2, “The Pharmacology of THC”) is that cannabinoid receptors exist in the brain and that they may be related to the opiate receptors. This would suggest that there might be naturally occurring cannabinoids in the human body. If this is true, then it is obvious that THC, the drug component of marijuana, works by stimulating the endorphins that regulate cannabinoid activity in the brain. However, as Iversen informs us, more research would be needed to establish this.

Iversen next discusses the effects of cannabis on the central nervous system. He describes both the mostly pleasurable, but sometimes frightening experiences that can occur, that marijuana can cause “double consciousness,” in which people can actually train themselves to act normally while intoxicated, and the temporary failure of working memory – though the ability to remember previously learned material remains unaffected.

With regard to medical marijuana, Iversen explains that cannabis was long used as a remedy for constipation, gout, malaria, rheumatism and other various pains in Eastern culture, but wasn’t taken seriously for its medicinal capacities by the West until the 1800s. Unfortunately, as doctors soon discovered:

The potency of commercial preparations varied from pharmacist to pharmacist as there was no means of standardizing the preparations for their content of the active drug. What proved to be an effective dose when using material from one supplier would either have no noticeable effects or would produce unpleasant intoxication.

Due to the problems involved with effectively isolating THC and other cannabinoids, getting a standardized cannabis-based medicine that doctors and governments alike would approve remains difficult. Synthetic analogues of THC are not much better as there is just as narrow a window between pain-killing effects and intoxication as with natural THC. Dronabinol (registered as Marinol), which is delta-9-THC but with low abuse potential, and Nabilone (registered as Cesamet), an analogue of THC, are both discussed in terms of helping chemotherapy patients to deal with nausea and AIDS patients to fight wasting syndrome. But it would appear that, despite considerable anecdotal evidence that marijuana helps chemotherapy patients and those with AIDS, multiple sclerosis, and glaucoma, other drugs exist that do not justify the use of cannabis.

Chapter 5, “Is Cannabis Safe?,” is self-explanatory. Although THC is determined to be safe with regard to toxicity, it is made clear that those with heart problems or existing mental illness should not use marijuana. Also, it is also evident that cannabis smoke differs very little in chemical and particle composition to tobacco smoke. As 96 percent of all recreational use of marijuana involves smoking the drug, it could be argued that, on the basis of the smoke alone, cannabis presents a health risk. Iversen also discusses the effects of cannabis during pregnancy, concluding that alcohol is by far the most dangerous to the fetus, but that “although the risks of exposure to marijuana during pregnancy do not appear to be great, it is surely better not to take any drugs during pregnancy, or to drink alcohol or smoke tobacco.” No argument there. Unfortunately, as alcohol and tobacco are legal, and therefore tests of their impacts on human health are easy to determine, the illegality of cannabis means that studies on the real impact of cannabis upon mental or physical health cannot be as effectively studied. Who is willing to risk arrest and prosecution under harsh drug laws by either conducting or participating in such studies, after all? Iversen stipulates that since marijuana has only been prevalent in the West since the 1960s, there may not be any conclusive evidence yet as to whether marijuana is truly harmful or not, even if contemporary research into the effects of cannabis were more solid.

Chapter 6 tackles the recreational use of marijuana and one study cited in particular would seem to confirm what the pro-pot crowd has long stressed:

Kandel et al (1996) surveyed 7611 students, aged 13-18 in 53 New York schools. Of these, 995 had experience with marijuana, but there was no evidence that this had any significant impact on their school performance or their family relationships, whereas the small number (121) of crack cocaine users showed significant impairments in both.

Iversen refers to another study of 2,794 young British cannabis users, of which 57.8 percent reported positive effects of their recreational use of cannabis – 25.6 percent of those cited relaxation and relief from stress as the reason they toked. Twenty-one percent reported problems, impaired memory, paranoia and laziness the main problems. Dependence and psychosis together represent just 1 percent of the problems experienced by the British stoners.

The concern over the increased potency of marijuana over the years – that today’s pot is not your father’s pot – is largely unfounded because THC is not toxic and, as Iversen aptly says, “But is this [increased potency] necessarily a matter of concern? Looking at some of the positive aspects one could argue that if people are going to consume cannabis illegally, then is it not better that they consume material that has been grown under clean conditions?” It is hard to find fault with that point. Also, the higher the potency, the less of a joint a person needs to consume to get the desired high, thereby inhaling less smoke.

The much-argued point as to whether marijuana is a “gateway” drug is aptly referred to by a quote from drug researchers Zimmer and Morgan that Iverson provides:

[M]ost people who ride a motorcycle (a fairly rare activity) have ridden a bicycle (a fairly common activity). Indeed the prevalence of motorcycle riding among people who have never ridden a bicycle is probably extremely low. However, bicycle riding does not cause motorcycle riding, and increases in the former will not lead automatically to increases in the latter. Nor will increases in marijuana use automatically lead to increases in the use of cocaine or other drugs.

Although THC triggers dopamine release similar in fashion to the opiates and the similarity of the cannabinoid and opiate receptors of the brain may explain some cases of dependence on marijuana where they exist, it is a poor argument for the “gateway” theory. This is much more of a personality problem than a problem specific to cannabis. In fact, as Iversen states, parental and peer influence are the prime factors. Through a combination of both, kids will try tobacco and/or alcohol at age 12, and then move on to marijuana at the age of 15. Whether they stop with cannabis or move on to cocaine or heroin is very much dependent upon societal and personal influences. In fact, according to this, are not alcohol and tobacco – legal drugs – “gateways” to marijuana use?

The seventh and final chapter, “What Next?,” is also self-explanatory. Iversen provides a history of official early reports into cannabis usage and effects, most notably the Indian Hemp Drugs Commission Report in 1894 commissioned by the British, The Marihauana Problem in the City of New York report by Mayor La Guardia in 1944, and the British Wooton Report in 1968 – all of which stressed that cannabis wasn’t, after all, a drug that made people crazy and which condemned its prohibition. But American and British anti-drug lords temporal ignored and rubbished these reports simply because, in each case, it is not what they wanted to hear. The de facto (but by no means de jure) legalization of small amounts of cannabis in the Netherlands since 1976 is also discussed. Iversen determines that it is still too early to tell how successful the Dutch experiment has been, but he appears to think that it has done more good than harm.

Iversen ends the book asking what fate cannabis may face in this, the twenty-first century. He mentions that opinion polls in both the U.S. and Britain overwhelmingly favor a relaxing in the laws governing cannabis and cannabis-based medicines, and that such moves also enjoy substantial support in the medical community who are justifiably frustrated by marijuana’s illicit status. But he also concludes that clinical research in the States and Europe will continue until, perhaps one day soon, trials appear so positive that governments will have to follow in line with the wishes of the citizenry. Other matters are discussed too: The specter of marijuana encouraging idleness (as opposed to the aggressiveness that is fuelled by alcohol), the risk of more people becoming dependent on cannabis if marijuana use became more widespread, the treating of marijuana possession and usage as a crime as a reflection of unnecessarily harsh public policy, and the fact that 80 percent of all drug offenses are for cannabis possession and usage. Iversen eventually concludes, “Perhaps the compromise that we are most likely to reach in the foreseeable future would be something resembling the Dutch experiment – a grudging acceptance that cannabis has become part of our culture, but falling short of full legalization.”

At the end of this richly factual book, my own attitude to cannabis has not changed. I have been given a lot more insight as to why marketing a cannabis-related drug is so hard and can appreciate the both the positive and negative effects upon one’s health from using marijuana. My personal belief is still that it should be decriminalized (if not legalized). If you are prepared to accept personal responsibility for smoking it, as most do, and are otherwise fit and healthy with no history of mental illness, then you should be allowed to use it.

Even though five years have passed since its publication, The Science of Marijuana is still a wonderful contemporary study of cannabis and I thank Dr. Iversen for helping to embolden my position on this particular drug. It deserves to be read by anyone who is truly interested in knowing the truths, not hyperbole and misinformation, about marijuana.

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  • Dean

    Great review, thanks for the summary.

  • Dr. D

    This article was a huge waste of my time. This is pseudo science at its finest. Thanks for re iterating a terrible (incorrect) book.

    • What exactly is your problem here in 2013 with this 8 year old review of a book published 13 years ago?

  • cg

    I have been a daily pot smoker for about

  • Ryan Deller-Smith

    Cannabis should be legal every where why?
    1. it grows in the ground and nothing added where as alchol is man made and is addicive.
    2. It is not a gateway drug tobbaco is, alchol is and these are legal.
    3. Cannabis does have medicinal propities
    4. If you are stoned it can be harder to pick a fight but when you are stoned you don’t want to fight.
    5. The hemp plant is so vesitile you can use it for so many things, not just for fun

    any other points please add them on

  • Freddy

    Marijuana does 3 things to people. You get happy, hungry, sleepy. In me and my friends’ experiences none of us have ever gotten in fights while baked, unlike when drunk. At no point have I ever felt like playing with guns, jumping out of a window, or running over a 6 year old girl in my car. We turn on South Park, heat up some hot pockets, and laugh for a little while then call it a night and go to sleep.

  • Coughing Often

    I just wish the british government and particularly the Daily Mail would stop being so foolish with regard to marijuana. Do a websearch for ‘gritweed’ and youll find many articles discussing the fact that some of the supply of marijuana in the UK is dangerously contaminated with particles of a glass like substance. I am one of many people (your own kids could be next) who is suffering now with severe lung and throat problems. Because of this I feel really strongly that cannabis must be legitimised within our society. The quality control and licensing of growers that would be a part of that process would ensure the safety of the public who enjoy the intoxication of marijuana. If cannabis were legal, we wouldnt have a problem about the young people using it, or the problem about the strength becoming too high, or the problem about the ‘gateway’ factor, or the problem about the dangerous contaminations. Please Please see sense people!!!

  • I think that’s a good point with regard to teens and young people thinking that other illegal drugs must not be so bad, simply because they’ve experienced nothing harmful with marijuana. I agree that we must be careful. We must let young people know that what’s true in marijuana’s case is NOT the same for other drugs. Other drugs are far more addictive and have far greater potential to cause harm to themselves or others. Even cannabis itself can affect people badly, and they must be aware of this. With cannabis legalization or even decriminalization comes great responsibility, and I wouldn’t support such a measure unless I was sure that protection for the vulnerable was effective.

  • infectedhack

    I would have to say that im on the side of marijuana. I my self have toked it for over a year. I dont see any more harm in toking then in smoking a cigerate. I do think cocaine, heroine, ice, ect. strong drugs are bad and should be kept illegal.

    BUT i think showing teens/kids that an “illegal” drug like marijuana (for those who tried it) is not harmfull. GIves them the idea that other illegal drugs must not be as bad, leading them to trying cocaine, heroine, ice, ect. By putting it in this same “catagory” is wrong (illegal drugs). AS we all know that marijuana has no addiciton like cocaine, heroine, ice, ect. but putting this false infromation about marijuana addictionn my have them (teens/kids) thinking that cocaine, heroine, ice, ect. doesnt either when in the end it does and that is what is killing our nation.

    TEll me what you think about what i have said.

  • nokko

    i lov drugs

  • Satori

    Looks like a great book, will have to check it out.

    I think it sucks that mj is so demonized, people need to re-lax already. While I’m not convinced the stuff necessarily does more good for your health than harm, I’m not very convinced that it will kill you or significantly mess up your life either. But I should point out, the amount that one consumes is key here. I’ve known casual tokers, every day but low-dose tokers, and chronic high-dose users. There is a world of difference between them.

    The jury is still out on whether or not moderate drinking has an overall good or bad effect, new studies lean in one direction or the other all the time so it’s hard to say. BUT, we seem to have enough confidence to say that moderate drinking probably won’t kill you. If it does you some good along the way (even mental benefit) then hey, that’s a bonus.

    I think the same logic needs to be applied to mj.
    What are the drug-war right-wingers actually saying about mj anyway? They seem to only talk about the high-dose chronics, as if this represents the vast majority of pot users. It does not.

    We wouldn’t think of banning reponsible and moderate users of alcohol from the stuff just because X% of people who try it become alcoholics. Taken to the extreme, anything can be potentially dangerous. I’m pretty sure someone who smokes too much pot is probably better off than someone who gets obese from fast food every single day.

    Personal responsibility anyone? Why punish the moderates for the actions of those who take something to an extreme? I wouldn’t want to live in a society where I couldn’t have a drink or big mac if I wanted it, and let’s not fool ourselves here, mj is really on that level of potential personal endangerment (even less than alcohol, in fact), we aren’t talking about meth or crack here.

    It’s not not killing anyone, and most people are responsible with it and they lead full lives dispite their mj use, then leave them alone and let them be happy in the way of their choosing. Mj is part of human culture and like it or not it’s here to stay. Time for everyone to get used to this hard FACT.

  • Marijuana is umm, what was I talking about?

  • Jadester: “[T]he government is now looking at upping the classification of cannabis once more. At the same time as seeming to be more than happy with our alcohol problem…”

    Too true, Jadester, too true. It’s very frustrating.

  • “…a grudging acceptance that cannabis has become part of our culture, but falling short of full legalization.”
    The funny thing is, here in England, we’re almost at that point anyway.
    Although, somewhat disappointingly, the government is now looking at upping the classification of cannabis once more. At the same time as seeming to be more than happy with our alcohol problem…

  • In my opinion, marijuana prohibitions demonstrably protect manufacturers of inferior products and harm consumers, violating long established antitrust common law prohibiting restraint of trade.

    Cigarettes manufactured in America are legally allowed to contain Polonium 210, and the ingredients of cigarettes are not required to be listed. Of course, tobacco smoke also contains nicotine, a deadly poison.

    Nicotine and Polonium 210 are known carcinogens. The Volcano vaporizer demonstrated an almost complete elimination of the only toxic properties in cannabis smoke, including polycyclic aromatic hydrocarbons, benzene, bezo(a)pyrene, toluene and carbon monoxide.

    Also, note that those promoting hysteria surrounding cannabis and schizophrenia are careful not to suggest that the 80 PERCENT of schizophrenics that self-medicate with tobacco ought to be arrested in order to send a message to children.


    The U.S. Office of National Drug Control Policy is running paid advertisements claiming that cigarettes are safer for kids than a joint, copy and paste the link into your browser to read more:

    http://www.mpp.org/releases/nr20050414.html and here

    Perhaps not coincidentally, tobacco firms originally funded the Partnership for a Drug Free America, (www.sumeria.net/politics/pdfa1.html ) which currently publishes pharmaceutical companies as 15 of their top donors:


    see also: http://www.cannabisculture.com/articles/4258.html

    Altria is by far one of the world’s largest political contributors:


    The products that would compete with cannabis kill millions globally, every year:

    from: worldbank.org/

    “The annual global tobacco death toll is already about three million–about 1 million in developing countries– and will rise to more than ten million by the 2020s according to current trends. Most of this increase will occur in developing countries. Of all the people aged under 20 alive today in China, 50 million will die prematurely from tobacco. For men, the epidemic of premature death from tobacco has already become substantial in all developed countries. The death rates in middle-aged men from all causes are especially high in eastern Europe”

    Of course, Altria owns Kraft Foods, another manufacturer selling products that would otherwise be forced to compete in a legal market with cannabis. This industry makes extra profits thanks to defective, dangerous and deadly ingredients (partially hydrogenated oils, saturated fats, excessive refined sugar):


    Drug war IS crime. Any questions? Perhaps they ought to be disclosed: