
New study makes link between use of potent cannabis and psychosis - m_eiman
https://www.thejournal.ie/cannabis-psychosis-study-the-lancet-4549656-Mar2019/
======
Daviey
This study is published in the Lancet (
[https://www.thelancet.com/journals/lanpsy/article/PIIS2215-0...](https://www.thelancet.com/journals/lanpsy/article/PIIS2215-0366\(19\)30048-3/fulltext)
).

My interpretation of their findings is that it doesn't provide safe assertions
that Cannabis is the cause or the effect.

Or in other words, does Cannabis usage create psychosis or do people with
psychosis choose to use Cannabis?

Similarly, there are unknowns with mental illness and tobacco smoking. Some
think that those with mental illness are more likely to smoke as self-
medication.

[http://ash.org.uk/download/smoking-and-mental-
health-2/](http://ash.org.uk/download/smoking-and-mental-health-2/)

~~~
Uberphallus
Exactly. It just basically says, from the people who requested mental health
care, more of them used cannabis than from the control group. Great. They also
present higher rates of smoking, alcohol use, self harm, obesity, and various
disabilities. Some may be cause, some consequence, some none of them. The
title is correct, there is a link, but that link has not established causality
of any kind. This is basically repeating uncountable studies saying the same
thing.

CBD, present in cannabis, is known to be antipsychotic, so the self-medication
hypothesis is pretty strong. It's the same case as nicotine, schizophrenics
have way higher rates of smoking, only because nicotine has a mild
antipsychotic effect, not because smoking turns people crazy.

~~~
aedron
Paranoia from weed is a well-known phenomenon among smokers, and was so even
long before clinical discussions about the effect became common. I'm surprised
how defensive some (usually liberal-leaning) people become when the connection
is suggested. I guess they have limited experience with cannabis, or they feel
the need to protect a certain narrative.

~~~
shkkmo
Or they like good science that doesn't attribute causality without evidence?
"Cannabis use increases the chance of psychosis" is just one of the three
potential relationships. The other two are "The chance of psychosis increases
cannabis use" and "A third factor increases both the use of cannabis and the
chance of psychosis".

In reality, the effect is probably not just one, but some mixture of all
three. It is extremely likely that people are self-medicating against
psychosis with cannabis, that cannabis can increase the risk of psychosis in
some people, and that the risk of psychosis is usually co-morbid with other
mental health issues for which people also self medicating.

A study like this does nothing to help us understand the link, but yet the
Authors seem willing to make strong claims about that link:

> The researchers suggested that if high potency cannabis was no longer
> available, the incidence of psychosis in Amsterdam would be expected to
> halve from 37.9 to 18.8 per 100,000 people per year, while in London, it
> would fall from 45.7 to 31.9 per 100,000 people per year.

That is irresponsible and bad science. It should be called out as such.

------
cranberry_juice
This is an old recycled study and far from being scientific. They assume
causal relationship (yup!) and it's based on surveys. It basically looks like
the authors had their pet theory and then build the paper around that to make
a perfect headline maker to fuel government agenda. The simple fact that
people with mental health issues self-medicate wouldn't stroke
prohibitionists. Cannabis is so popular that person with issues sooner or
later try it and find it helps them. This study is essentially the same as
finding people taking paracetamol for headache and saying paracetamol causes
headache. The stronger dose people take, the stronger headache they have.

I think publishing such things should be illegal because it causes harm to
public.

The original study:
[http://www.thelancet.com/pb/assets/raw/Lancet/pdfs/14TLP0454...](http://www.thelancet.com/pb/assets/raw/Lancet/pdfs/14TLP0454_Di%20Forti.pdf)

~~~
ada1981
They may look deeper and see that childhood trauma is a predictor for
psychosis. And many people who are dealing with trauma symptoms find relief in
cannabis.

------
clydethefrog
Because of a history of psychosis in my family I decided to never take drugs
in my life, not even cannabis while I life in a country where it's legal. I
still got a heavy psychotic episode last year. Turns out the (heavy) drinking
I participated in my student life was to blame. Research has shown that
alcohol abuse causes an 8-fold increased risk of psychotic disorders in men
and a 3 fold increased risk of psychotic disorders in women. [0] Not telling
this to undermine the danger of cannabis for psychosis, but I wish I knew
alcohol is unresponsible too I you have a high risk for psychosis. Sleeping
enough, excercise, healthy diet and not numbing my stress with any substance
has greatly helped as well.

[0] [https://en.m.wikipedia.org/wiki/Substance-
induced_psychosis](https://en.m.wikipedia.org/wiki/Substance-
induced_psychosis)

~~~
pennaMan
>I decided to never take drugs in my life

>the (heavy) drinking I participated in

You can clearly see how damaging the anti drug propaganda is when people don't
even consider alcohol the hard drug that it is.

~~~
clydethefrog
Yes, I learned it the hard way. My reasoning was that alcohol doesn't "free"
your mind like cannabis or LSD does, so I will not trigger psychosis. But it
still has effect on your brain chemistry.

~~~
alex_hitchins
But alcohol can cause psychosis - Delirium Tremens :
[https://paihdelinkki.fi/en/info-
bank/articles/alcohol/deliri...](https://paihdelinkki.fi/en/info-
bank/articles/alcohol/delirium-tremens-and-other-alcohol-psychoses)

~~~
johnisgood
It requires you to be physically dependent on it, and then delirium tremens
may occur _following abrupt cessation_ , as a withdrawal symptom.

The two cases at hand are different.

------
macawfish
Argh, this is an annoying, seemingly politically motivated report.

The relationship between common cannabinoids and psychosis is already quite
well understood.

At large enough doses, THC is psychotic and CBD is antipsychotic (likely CBG
too), so much so that CBD is used to treat positive schizotypal symptoms.

E.g.
[https://www.researchgate.net/publication/51146763_Cannabis_w...](https://www.researchgate.net/publication/51146763_Cannabis_with_high_cannabidiol_content_is_associated_with_fewer_psychotic_experiences)
and multiple studies

I hate seeing science abused for political reasons, and this study is ripe for
that.

Why doesn't the study talk about the reason those high THC strains are so
popular in the first place? That to me is the real tragedy. Ultra high THC
strains are the "moonshine with too much head" of cannabis prohibition.

------
blastbeat
Where I grew up, basically every youngster did drugs to escape the boredom of
the 90s, as being trapped in their smallish german home towns. People did
mostly cheap drugs like cannabis, binge drinking, magic mushrooms and crystal.
Many of them eventually abandoned their habits, apparently without much
damage. But I know quite a few who suffered from drug-induced problems like
psychosis at some point in their life. Many of them are basically disabled
now. Some of them live still with their parents, condemned to take medication
for the rest of their life. All of them smoked weed, but only one of them
smoked it exclusively. In the other cases where in addition drugs like crystal
meth involved.

My guess is, that for some people those drugs act like a tipping point, and
bring underlying problems into full blossom. In my case, it was developing an
anxiety disorder. Thus, as you don't know where or what your tipping point is,
I'm strongly against taking those drugs. Even a one-time experiment with
mushrooms can wreck your life.

~~~
mg794613
Sorry, I agree with your full statement except the last 5 words. Did you hear
this from someone who knows someone or do you have the science for that?
Because as far as I know, all scientific research on psilocybin conclude the
same. If you have experience where someone "became weird after first use" they
were probably already weird but hiding it from you.

~~~
clydethefrog
Mushrooms are banned in the Netherlands because too many tourists died from
incidents involving the drug. I figure many of those tourists used it for the
first time.

~~~
thedaemon
Please link your sources. I do not know of anyone dying from mushroom intake.

~~~
clydethefrog
>Nevertheless, medical intervention was needed for 149 incidents involving
mushrooms in 2007, an increase of 19 percent over the previous year. In 2005
there were 70 incidents. Among the high-profile cases was an incident in which
a Danish tourist raced his car across a crowded camping. Several tourists
jumped or fell from hotel windows.

>In the case that led Ab Klink to propose the ban in October 2007, a 17-year-
old French girl committed suicide by jumping from a bridge into busy traffic.
It was later revealed that the girl, not old enough to legally enter a smart
shop herself, had asked a friend to buy her some mushrooms.

[http://www.dutchamsterdam.nl/662-mushrooms-ban-amsterdam-
net...](http://www.dutchamsterdam.nl/662-mushrooms-ban-amsterdam-netherlands)

~~~
mg794613
I was sort off hoping you would give those examples. The devil is in the
details here. We have a long history of problem with tourist coming to
Amsterdam and live like animals. Simultaneously in 2007 after a long time of
having barely any seats in Amsterdam, the CDA (Christian Democrats) were
looking for a reason for a stricter drug policy. Now I do agree with having
more control on the abuse of the freedoms in our city, but I am convinced the
ban on mushrooms has been a superficial fake solution. Yes, mushrooms are no
longer being sold in the city, but now it's "truffels". The bigger problem, as
was in this case with the unfortunate French girl, people come here and have
absolute no control. What has been conveniently left out of this story is that
the girl was already depressed and had been partying for days. Mushroom usage
has been a very safe practice for millennia and some party girl and zealous
political party ruined it for us.

------
y0y
I know this is 100% anecdotal, but a good friend of mine who was a brilliant
programmer discovered cannabis in his late 20s after moving to the bay area
for a well earned high-paying gig. Prior, to my knowledge, he didn't even
drink alcohol. After about a year of extremely high dosages, something in him
snapped. He just lost his mind. He became convinced the internet was sentient
and was speaking through him and all kinds of other nonsense. He's been under
psychiatric supervision near his family home back on the east coast ever
since.

Again, it's anecdotal, and there could be a myriad of contributing factors - I
know he had also begun drinking during that time period. But, until this
happened, the idea of anyone going mad from cannabis was laughable to me. Now,
I think about him sometimes when I'm visiting legal states and indulge myself
in some quality edibles.

~~~
aedron
Apologies for repeating myself from elsewhere in this thread, but the
'paranoid from the weed' effect is extremely well known among smokers. I feel
the need to stress this, coming from someone who has had more experience with
weed, both personally and from social circles, than probably most in this
forum (even accounting for the California contingent).

Some can deal with it easily and are unaffected, many are eventually a bit
debilitated by it, and for some it triggers major problems. No need to sweep
this under the rug.

~~~
fjabre
Yes but paranoid doesnt mean psychosis. Inexperienced users will tend to get
paranoid more so.

I believe people with psychosis are drawn to weed as they are to other
substances.

This study adds nothing new. It just demonstrates that people predisposed to
psychosis are more likely to smoke weed. Anyone here could've told you that
without a study being done. There is no cause and effect demonstrated in the
paper.

Notice they did not say smoking weed causes the psychosis even though they
found a 'strong' link.

~~~
aedron
I'm no expert, but isn't paranoia one of the most significant, if not the
primary, characteristic of psychosis? If cannabis triggers one, I'd say the
'strong' link is well warranted.

~~~
UncleEntity
I think you can be paranoid on the pot and not be suffering from psychosis.

I've seen it many a time and never seen someone have a psychotic episode.

------
dangerface
Why does all the research on cannabis and psychosis always rely on correlation
as if its causation? This isn't the first study to prove this correlation, and
then let the media imply causation.

If truth was their goal why keep doing the same broken study with pitiful
sample sizes. 2000 samples is too small to a/b test a site, but good enough
for a medical study?

If high strength cannabis made you five times more likely to have psychosis,
then it follows that countries like America, Spain and Netherlands should have
psychosis rates five times higher than other countries, but it's about 1%
world wide[1].

Obviously you would need to take into account population and other proven
causes of psychosis such as alcohol[2]. Similar studies have been done[3] with
much larger sample sizes than these clowns.

[1] [https://www.mentalhelp.net/articles/schizophrenia-
symptoms-p...](https://www.mentalhelp.net/articles/schizophrenia-symptoms-
patterns-and-statistics-and-patterns/)

[2]
[https://gateway.euro.who.int/en/indicators/hfa_390-2401-numb...](https://gateway.euro.who.int/en/indicators/hfa_390-2401-number-
of-new-cases-of-alcoholic-psychosis/)

[3]
[https://ebmh.bmj.com/content/15/4/105](https://ebmh.bmj.com/content/15/4/105)

~~~
DanBC
> If high strength cannabis made you five times more likely to have psychosis,
> then it follows that countries like America, Spain and Netherlands should
> have psychosis rates five times higher than other countries, but it's about
> 1% world wide[1].

You're not counting actual prevalence of psychosis. You're counting prevalence
of diagnosed psychosis.

Also, cannabis doesn't increase risk for all types of psychosis. There are
different types. Cannabis only increases risk for one or two types of
psychosis.

~~~
dangerface
> You're not counting actual prevalence of psychosis. You're counting
> prevalence of diagnosed psychosis.

True but the countries I listed are first world countries where accurate
diagnosis is common.

The third reference I give is to a study on the prevalence of psychosis across
52 countries. It takes in to account that in developing countries diagnoses is
uncommon and not accurate, any decent study would do this. The world health
organisation study I linked used a sample size of 200,000 compared to the
2,000 sample size the cannabis study used.

> Cannabis only increases risk for one or two types of psychosis.

Then the study should only target those types of psychosis.

Yes other studies with larger sample sizes have proven this correlation
before, but correlation in itself is meaningless. My argument was that if they
really wanted the truth they could have done a study to show causation, but
instead they showed correlation using quack sample sizes and then a bit of
choice wording to scaremonger.

The fact that people with psychosis are more likely to smoke cannabis, doesn't
mean cannabis will increase your risk of psychosis. It just means people with
psychosis are more likely to smoke cannabis.

------
keiferski
Western society has a serious issue with nuance. No, we should not throw
people in jail and ruin their lives for smoking cannabis. Yes, cannabis has
some health benefits for specific people in specific circumstances. No, that
doesn't mean that cannabis is somehow "good for you" in the standard sense of
the the term.

This is why the "health benefits" arguments for legalization of drugs are
generally a bad route to take. It would be far more fruitful to argue for
legalization based on individual responsibility, personal choice, and related
themes.

~~~
Al-Khwarizmi
To me, the best argument (not only for cannabis, but for stronger drugs too)
is that illegalization has been tried for a long time and it just doesn't work
in practice.

I don't consume any drugs other than alcohol and don't have any interest in
doing so, but if I did, it would be trivial to obtain them in my (smallish)
city. Everyone knows where to go.

So illegalization doesn't meet its purpose (making drugs difficult to get) and
yet it does have negative effects (the drugs sold have no quality control at
all -which often causes deaths-, pay no taxes, are sold without any legal
warranty, etc.) I'd rather they were sold in pharmacies, being dispensed
together with reliable information (like tobacco), forbidden to minors (which
could actually work reasonably well, because no one would go to the trouble of
setting a black market exclusively to sell to minors) and paying taxes that
could be used to fix the problems they cause.

To me, this is enough grounds for legalization, regardless of the exact health
effects of drugs.

~~~
betterunix2
"...illegalization doesn't meet its purpose (making drugs difficult to
get)..."

This is a common assumption about the purpose of drug prohibition, but
historically things are more complicated. Racism played a much bigger role in
drug prohibition and the war on drugs than genuine concerns about public
health. The basic concept is that some non-white group is corrupting white
youth/white women with drugs; therefore, to protect white people, the police
are empowered to imprison/kill those scary drug peddlers. On some level it was
about making drugs harder to get, but the assumption was that white people
have no interest in drugs until some non-white person pushes it on them. The
assumption was always that the impact of drug prohibition would be mostly
concentrated on non-white populations.

~~~
antt
This does not explain the situation in Europe, South America or Asia, all of
which have (or had) laws similar to the US for drugs.

~~~
mywittyname
To my knowledge, these are all US-imposed policies.

~~~
mirimir
You don't want to piss off the US.

------
idlewords
Don't many psychotic and schizophrenic people self-medicate with cannabis?

~~~
n0mad01
that may be true. it may also be that too much cannabis is bad for you. as is
too much sugar/food, sport, sitting, sleeping or ... anything.

~~~
puranjay
Somehow, if you suggest that smoking too much weed is bad for you, you're
branded as some sort of puritan who isn't "getting with the times". I have
never seen the kind of propaganda for any substance as I have for weed, with
almost zero discussion about its harmful effects.

~~~
vanderZwan
> _with almost zero discussion about its harmful effects._

Where do you live? Because growing up in the Netherlands I can say all the
negative side-effects were very clearly explained to us in high school,
without stigmatizing it.

EDIT: it is a sincere question - obviously the Netherlands is in a kind of
special position here. And my experience is from the late 90s, so who knows
how things have changed since then too.

~~~
ddorian43
Do people know about drug induced psychosis there (including weed)?

The lightest strain in a coffee-shop was pretty strong.

~~~
vanderZwan
First, we should keep in mind that I can only speak anecdotally and by
extension of that only for people with a higher education.

But with that said, yes, we do. I even know someone who had it, and they quit
using weed after that. It's kind of treated like the complicated thing that it
is: genetics and existing mental and physical health are all risk factors, and
as a teenager there is the still-developing brain to consider (just like with
alcohol). You basically have to decide for yourself if all of that seems worth
it.

------
notacoward
I love how when the topic is climate change or vaccines or diet/nutrition
everyone here is all "Science! Science!" but when the topic is adverse effects
of vaping or smoking pot the preponderance of comments are "This science
sucks!" Cherry-pick much?

~~~
alphakappa
A single study does not make science. It’s a data point but it needs peer
review, replication, and consensus after multiple independent studies.

Climate change has scientific consensus from decades of study across the
world.

~~~
notacoward
Funny how you picked that one example. Kind of proves my point, don't you
think?

~~~
jsutton
Not really, the amount of quality studies done in relation to climate change
dwarf those done around cannabis. Cannabis studies are still incredibly rare
due to its legal situation.

------
_Codemonkeyism
Talked to a psychiatrist some years ago, he said it would create the biggest
health crisis in Germany if cannabis would be legalized, as there is a strong
connection to schizophrenia for cannabis use. This link is only in a small
portion of people, but when millions start to smoke it's going to be a very
large issue Germany is not prepared to tackle.

~~~
bildung
The psychatrist doesn't seem to know much about schizophrenia. If you compare
worldwide prevalence [1], you'll see that the difference between countries of
lowest prevalence and countries of highest prevalence only differ by about a
factor of two. If you only compare developed countries, the difference is less
than 50%. So even if everyone in Germany would start daily consumption of high
THC cannabis, and IF that would be the only cause of schizophrenia besides a
societal baseline, there would be about 8000 new cases per year. If we assume
that each case costs about 16k EUR per year [2] for health care, that would
result in additional costs of only about 130M EUR per year. That's .003% of
GDP, so completely insignificant.

But what's way more important: The study shows that the only correlation is
with _daily_ use of _high THC_ consumption. No correlation with low THC
products (see figure 2 in the study). Results from e.g. the alcohol
prohibition and recent cannabis legalization in the US suggest the share of
high THC product would actually _decrease_ once cannabis would be legal in
Germany. So IF high-THC cannabis is the main cause of schizophrenia, it would
actually be probable that legalization would _decrease_ schizophrenia
incidence in Germany.

[1]
[https://en.wikipedia.org/wiki/Epidemiology_of_schizophrenia](https://en.wikipedia.org/wiki/Epidemiology_of_schizophrenia)

[2] [http://www.gbe-
bund.de/gbe10/abrechnung.prc_abr_test_logon?p...](http://www.gbe-
bund.de/gbe10/abrechnung.prc_abr_test_logon?p_uid=gast&p_aid=0&p_knoten=FID&p_sprache=D&p_suchstring=13064)

~~~
ddorian43
Going into psychosis you aren't working either. And schizophrenia will
decrease your lifetime working hours. So you need to add those too. And you'll
need $$ for disability (beside healthcare) to also help your children. And
housing etc. (not everyone, but many)

But yes, if the number of people is low it won't be a problem..

~~~
bildung
Actually many schizophrenia patients are in fact working and living relatively
normal lives. The costs I linked are the actual current costs for Germany and
include reimployment measures (have a look at the second link). But you're
right, it is of course an outcome we as society should try to prevent anyway.

My point was that there won't be a societal crisis, even if the assumption of
THC being the main cause of schizophrenia were true.

With or without legalization, better drug abuse prevention through education,
widely accessible addiction treatment and de-stigmatisation of mental health
issues are things we should strive for - because those measures actually
affect peoples lives for the better.

