Marijuana Reconsidered: An Interview with Dr. Lester Grinspoon


Dr Lester Grinspoon is associate professor emeritus of psychiatry at the Harvard Medical School. He researched the medicinal legitimacy of marijuana prohibition 45 years ago and discovered that an immense chain of lies served as a base for sending millions of people to jail. Since then he’s became an advocate for telling the truth about marijuana.

PATRICK DEWALS (PD): Can you tell me how you became interested in marijuana?

LESTER GRINSPOON (LG): Well it began in 1966. During my anti-Vietnam activism I met Carl Sagan and we became very good friends. When I met Carl Sagan I was convinced cannabis was a very harmful drug. Going to his house one day I discovered that he smoked cannabis and so did many of his friends. Now these were not unsophisticated people and I tried to tell Carl that marijuana was harmful, but he joyfully responded that it wasn’t harmful at all.

With this experience came the idea of writing a paper that summarised the medical scientific basis for marijuana prohibition. At that time [in the USA] marijuana prohibition was leading to the arrest of 300,000 people a year, mainly young people, 89% for simple possession. For me it became important this prohibition was justified. It was in the library of the Medical School I found out that I was completely wrong about the harmfulness of marijuana. Not only was it not harmful, it was remarkably nontoxic, and the drug itself was not causing harm to the user, unlike the policy of arresting people. Some went to prison for possessing it and others saw their career goals compromised.

I wrote an article about the subject and it was published in the International Journal of Psychiatry. One of the few people who read it was the editor of Scientific American. He asked me to reduce the article so it would fit in his magazine, to be published as the lead article in a coming issue. When my article was published in November 1969, it caused a huge tsunami so to speak that resulted in proposals from three different publishing companies for me to write a book about marijuana. Eventually I wrote my book, Marihuana Reconsidered, which came out in 1971, through Harvard University Press.

Doing the research for my book, I discovered marijuana was not harmful and I started to understand why people used it, what the attraction was. And I decided, at the age of 42, that I was going to use it as well. It was just too interesting an experience to let go. But I also knew that if the book was successful there would be a good chance I’d be asked to testify before a congressional session or senate committee. Because I didn’t want my own experiences with marijuana to make my testimony less objective, in the view of others, I decided to use marijuana two years after publishing my book.

And, indeed, I ended up testifying before a senate committee. I remember a big tall senator, who was rather doubtful about all I said, asking me, “Doctor did you ever use marijuana?” and I answered, “Senator, I would be glad to answer that question if you could tell me that if I gave you an affirmative answer would it make you more sympathetic to my answer or less?” He stared at me, “You sir, are being impertinent,” and he walked out the backdoor. Later that day, when I drove home, I said to my wife Betsy, “The time has come,” and sometime that week I experienced marijuana for the first time.

PD: You said earlier that through researching your first book you came to understand why people use marijuana. What are the reasons people use it?

LG: Most people are familiar with recreational use. Additional to this use marijuana has an ancient history as medicine. We know that Shen Nung, a Chinese emperor, who lived about 5,000 years ago, used marijuana as medicine. In modern Western medicine we had to wait until the mid-19th century for the introduction of marijuana through an Englishman named William O’Shaughnessy. At that time he worked in Calcutta and observed the indigenous people using marijuana as medicine. He began studies on animals to be sure it was safe and published the studies when he came back to England. Between 1849 – the year O’Shaughnessy published his first paper – and 1900 I came across about 100 critical papers on marijuana as medicine in my review of the literature.

The third use is the enhancement of a broad range of human activities. Everybody that has used marijuana knows an ordinary meal can taste like a culinary treat and it can enhance sexual experiences. These are enhancements right there on the surface. Once one becomes more experienced with cannabis, they can experience or appreciate phenomena in another way, for example, understand art in a better way, use it for creative purposes or deepen spirituality.

PD: When you published your first book Marihuana Reconsidered in 1971, which was a controversial book at that time, what were the reactions of your peers and other scholars?

LG: Yes, there was a lot of reaction. I remember the most significant of all. I was put up for early professorship by my chief at Harvard Medical School. At that time I already had published about 70 papers about schizophrenia and I had some expertise in this domain. When my chief came back from the promotions committee he told me committee members loved my work on schizophrenia but they hated Marihuana Reconsidered because it was much too controversial.

PD: Even with all the data that you used to support your work?

LG: Oh yes, I just couldn’t believe it, I said to him, “Controversial, what do they think of the scholarship?” When I was leaving his office my chief said to me, “They asked me to ask you a question, what are you planning to do next?” I said that I was an intellectual and I did not know yet, which was a kind of lie, but that I wanted to have the freedom to go my way. The affair resulted in the turndown of my candidacy for professorship and I had to wait till 1995 to become professor at Harvard, twenty years after my first candidature. In the beginning I was heartbroken but as I was not a professor I skipped a lot of department meetings and other things which meant I had a lot of time to do my own research. Because of the free time I started to become active against cannabis prohibition that was and still is very destructive in American society.

PD: What can you tell me about marijuana as an addictive substance?

LG: There are still people who think it’s addictive. They say about 10% of users become addicted. I don’t see it as an addictive substance. Sure you see some people using it all the time, especially many young people, but they do it because they haven’t figured out what to do with their lives. I used it for more than four decades, almost everyday, and when there were times I could not use it I did not encounter any problems…. I don’t believe there is such a thing as marijuana addiction but common people are very concerned when they discover their kid is using marijuana. They will get upset and take him to the psychiatrist. This doctor has no other choice but to diagnose the youngster as marijuana addicted, as is mentioned in the DSM, because without putting a label on the ‘patient’ he will not be reimbursed. People use this data to ‘show’ that 9 or 10% of marijuana users are addicted. I remember that one of my students who smoked marijuana decided one day to stop using it to prove to himself he was not addicted. I thought it was a good idea and I said to myself, let’s stop for 40 days and see how it goes. I had no problem at all. The people who insist marijuana is addictive are on very thin ice.

PD: Can cannabis cause psychosis or schizophrenia?

LG: Absolutely not! Schizophrenia is a disorder which one is born with but it doesn’t always manifest itself. It usually starts during adolescence. The one possible connection to schizophrenia is when people who are inexperienced with cannabis start smoking it and become anxious or paranoia which is, of course, uncomfortable. I imagine that with someone who is new to cannabis, it can act as a precipitating event. Many schizophrenics say their psychotic episode started after such a precipitating event. Those events can range from an automobile accident or the death of a loved one. And I can imagine, but I have never seen this, that the naïve use of marijuana can act as a precipitating event.

PD: What do you know about marijuana in relation to cancer?

LG: I am glad you bring that up. I hear a lot of people talking as if cannabis can cure cancer, and that worries me. People who are not educated on this will not go to a doctor and decide to miss other treatments and just rely on cannabis. By deciding this course of action, they in fact lose a lot of time because with cancer you need to act as fast as you can. I think you cannot say cannabis cures cancer. However, there are some properties of cannabis that in my view make it very important patients use marijuana alongside modern Western oncological treatment. In the case of chemotherapy, for instance, they can use cannabis to combat the side effects of the treatment such as distressful nausea. Cannabis can help to diminish the size of tumours which is important when the tumour causes an obstruction. It also stimulates appetite, and in vitro it stops cancer cells from spreading, kills cancer cells, leaves healthy cells untouched, and interferes with the blood flow in the tumour. So there are a number of effects showing that marijuana pushes back cancer. This makes it important to use marijuana but with modern medicine. Nobody has proven to me so far that cannabis cures cancer but for sure it is a very good adjunct.

PD: In Belgium, our minister of health, Maggie De Block, who is a doctor, says you can’t use marijuana as a medicine due to lack of proof. According to her, the only thing useful is Sativex and only for MS patients. What is your comment?

LG: Let me start with saying that Sativex is marijuana! To say that you could use Sativex and not take marijuana for a similar effect is silly. And to state there is no evidence is nonsense. There are mountains of anecdotal evidence, you cannot deny it. We are used to the idea that medicines come from pharmaceutical companies, after they do double blind tests. But this is a plant, and you cannot patent a plant and have an exclusive license to sell it. That’s why the pharmaceutical companies are not interested in doing expensive tests with marijuana because after positive tests anyone could bring marijuana-based medications on the market.

PD: Are you saying that marijuana is a great medicine for the people but not for the pharmaceutical companies, for them it is worthless?

LG: Absolutely! Another reason why you should not worry is marijuana is non toxic. I remember when I had for the first time a patient with Crohn’s disease; even after surgery she was still compromised in her work because of it. I said to her, I don’t know if marijuana will help you but I would try it. If it doesn’t help you it surely is not going to hurt you. And today, if you read the medical literature, it became a very important treatment for people with Crohn’s disease. Some people say to me you should not tell people to use marijuana for this or for that. But that’s silly because it might help you and surely will not hurt you. If it does help you, you are very fortunate because it has no side effects and it will always be cheap.

This article was published in New Dawn Special Issue Vol 10 No 5.
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„Dr Lester Grinspoon, a psychiatrist, is a retired professor at the Harvard Medical School and a well published author in the field of drugs and drug policy. He has authored more than 140 articles in scientific journals and twelve books, including Marihuana Reconsidered and Marijuana, The Forbidden Medicine (with Dr James B. Bakalar). Dr Grinspoon currently maintains, which chronicles real life stories of people who have had positive “non-medical” experiences with marijuana.

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About the Author

PATRICK DEWALS is from Belgium. He has a Bachelor’s degree in psychiatric nursing, a Masters in political science, and he’s a student of political philosophy. Patrick plans to write a thesis on ethics and medicinal cannabis. Twitter: @patrickdewals1 Email:

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