I expected quite a bit of push-back on my recent video. I've encountered marijuana proponents
before, but they still manage to surprise me. There was a lot of anger, a lot of defensiveness,
a fair share of personal attacks on me and my character or motivations, and one death
threat that was disturbingly specific.
That was not the norm, though. For the most part I was pleasantly surprised by the rationality
of the responses. People disagreed, some suggested I might be unconciously biased on the topic,
and others asked some really great questions. There were also a few people who shared with
me stories and personal anecdotes either for or against points raised in the video. Some
said they would forward the vid to friends or relatives. A few even said that I gave
them some motivation to quit. I want to extend a heart-felt thank you to everyone who watched,
considered the content and participated in the discussion.
I want to start off with one apology. I think it's been correctly pointed out that I misrepresented
the LD50 data comparison to nicotine. One was for oral and one was for inhaled dose
in the comparison. That's a bit sloppy, and that whole section was not well received.
Let me just amend that part to say that an LD50 for THC has been established. By my best
estimates, the median lethal dose of marijuana is somewhere on the order of 50 joints or
6 grams of THC. So far as I know, no-one has ever had their heart stop because they smoked
too much marijuana. There are documented overdoses from synthetic cannabinoids. I really only
intended to address the old saying that it's impossible to overdose from THC because it's
so safe. It's certainly impractical, but what protects the user is not the safety or non-toxicity
of THC but the low density of the drug and how it affects the body.
There were also two really important issues raised as deficits in the video. One, I didn't
address the threshold of usage. How much pot is abuse, and how much is okay. Two, are the
other forms of use, things likee vaporizing and ingesting safer? The short answer to both
is "I don't know". There's not much data on very low consumption and the definition changes
from paper to paper. Any amount of the drug is going to have effects on the brain, but
not all DNA damage necessarily leads to cancer. Smoking a plant is always going to release
toxic compounds into the lungs. Vaporizing or ingesting just aren't well studied in the
literature. Human clinical studies are not very good at detecting very small differences
in risk in a behavior because there are so many variables in the way people live their
lives. I can only say that smoking is probably never a good idea, that we don't know how
much is too much, and you'd be better off with a healthy habit instead of a bad one.
I'm going to address the accusations of cherry-picking at the end of this video, because I found
that to be the most common, and frankly the most offensive accusation. It's important
that a scientist always be ready to concede bias, but I want to let you, the viewer, decide
if I unfairly cherry-picked studies or if I'm fairly representing the most recent research
on harmful effects of smoked marijuana.
Before I get to that, there were a couple of common misconceptions that I want to address.
1. There were a lot of people who were quite insistent that marijuana is less harmful than
tobacco or alcohol and that somehow invalidated the research presented.
Let every drug be considered on its own merits. Just because heroin is worse than cigarettes
doesn't make cigarettes a safe alternative to heroin. Just because you suspect that marijuana
is better than cigarettes does not make marijuana a safe alternative to tobacco.
One of the best questions asked in comments was how marijuana and cigarettes compared,
especially in cancer risk. It seemed like I was saying that they were equal per unit
mass, like one cigarette equals one joint, but that's not the case. One joint contains
twice the cancer causing compounds of cigarette, but the method of smoking is much worse. The
New Zealand study in 2008 did a case control study of about 400 people. After they made
corrections for tobacco smoking, the risk of lung cancer was increased by 8% for every
joint per day they smoked. This was the same risk increase as smoking a pack of cigarettes
a day. The people in the study who smoked the most pot were also the most likely to
develop lung cancer.
I want to be very clear that older studies have failed to find the same correlation in
other populations. The ratio of the studies I looked at was about 2 to 1 in favor of pot
smoking increasing risk. The biggest differences in the studies are the age of the subjects.
Lung cancer is a long-term development, but before cancer develops, people who smoke marijuana
exhibit abnormal cells in their lungs, specifically alveolar macrophages, the kind of abnormalities
that can progress to cancer. The hardest part of studying this is untangling the cigarette
and marijuana use of people who use both. However, scientists are not stupid. There
are statistical methods specifically for accounting for multiple variables, and researchers think
through their models very carefully.
2. A lot of people informed me that I was wrong about marijuana being addictive. They
based this on their intuitive knowledge or their personal experience. I can only say
that repeated studies have demonstrated that a percentage of people experience withdrawal,
and many people are actually unable to quit. Why do the scientists think they know better
than YouTube commenters? Because they send out surveys, they interview users, and study
behaviors of patients in recovery.
Now you are welcome to dismiss this research because it conflicts with your personal experience.
You can accuse the researchers of being dumb, being biased, or making the results up. You
can even dismiss all research as being invalid. However, if you give yourself that kind of
easy excuse, you can dismiss anything you disagree with out of hand. It's a rationalization
and it causes you to lose your objectivity. Better to face evidence with honest openness,
even when you disagree or the results are hard to hear.
The other common objection to cannabis addiction is that everything is addictive, including
sugar and love, or that marijuana addiction is just people missing their emotional crutch.
You are welcome to use this argument as well, but be sure to apply it consistently. The
symptoms of withdrawal in marijuana are very similar to the symptoms of withdrawal in cigarettes.
They are physiological changes in the organ systems of the body. Would you say that cigarettes
are only psychologically addictive?
3. The schizophrenia link was contested by a lot of people as well. The most common argument
was that marijuana couldn't cause psychoses, but it can make the symptoms of a pre-existing
disorder worse. That's actually an interesting paradox. Some diagnosed schizophrenics actually
benefit from marijuana when compared to their non-drugged state. A common cause of self-medication
is to cope with hallucinations. However, the mechanism of how marijuana acts as a component
cause is well documented. Let me define that term: component cause is a cause that is not
sufficient alone to cause the disease, but in context with other risk factors is actually
causative. More on this at the end.
4. There were a lot of anecdotes shared with me about how marijuana made a friend smarter,
or cured his emphysema, or removed her warts. I think that's great, but A, that's not relevant
for the harmful effects, and B, anecdotes are interesting, but not always useful in
objective analysis. If you're a student of human psychology, you know that people tend
to be very poor at determining causation, we remember the hits and forget the misses.
Your experience may not be typical, which is why scientists use large populations, randomly
selected, and aggregate the results.
Now we get to your chance to judge my bias. What I'm going to show you here are the first
ten papers for "cannabis and schizophrenia" found on PubMedCentral. Let me be very clear.
I typed in the terms cannabis and schizophrenia in the search bar, and these are first ten
hits in the database of full-text research papers from around the world. I'm not asking
if you agree with the findings of these papers, I'm asking if an honest person could read
through these ten papers and still agree with the conclusion that cannabis is addictive
and plays a role in the development of schizophrenia. I invite you to follow the link in the bar
below and verify that I'm not manipulating anything here. Now, am I cherry picking or
accurately representing the body of knowledge?
I could repeat this exercise for cannabis and lung cancer, cannabis and addiction, cannabis
and heart disease, etc.
For now, I'm done with marijuana. It's been a pretty painful experience facing down dozens
of angry denialists.
I've been asked to do a video on alcohol and its harmful effects, and then possibly for
cigarettes. I doubt that I will have to face so much rationalization, so I'm actually looking
forward to it. In the short term, I have an essay by Einstein, a discussion of MSG in
food, and I'm also looking into aspartame. You can also look for a discussion of evolution
and a little bit about my work with NASA.
Again, I want to thank those of you who have reached out to me in a positive way. I make
the videos on topics you request, even if it kills me.
Thanks for watching,