March 21, 2007

UK Charity Pushes for National Cannabis / Marijuana Education on Link to Schizophrenia

The UK mental health advocacy organization RETHINK (roughly equivalent to NAMI in the US, and Schizophrenia Society in Canada) stepped up the pressure this week for a national education program on the link between cannabis / marijuana use and increased risk of schizophrenia. At we think that such education efforts are important, but that they should be expanded to all the key factors that have been linked to increased schizophrenia risk - especially prenatal care, and child development (see schizophrenia prevention for more information).

The mental health charity Rethink stated that at least five international studies have found cannabis use at this age doubles the risk of mental illness. Some research suggests those who have used cannabis more than 50 times have six times the usual risk of developing schizophrenia, the charity says.

A spokesman for Rethink said: "We now know that cannabis can be a trigger for mental health problems and smoking it under the age of 18 can double people's chances of developing psychosis.

"The Government must invest in a wide-scale public health campaign so that young people know cannabis is not risk-free."

Rethink, in a recently published article, says that for those with severe mental illness, using cannabis greatly reduces your chances of getting better. It says:

Smoking heavily at any age is associated with mental health problems.

Cannabis does not cause psychosis in everyone who uses it. One study has suggested that this is because of people having different genes, but this has not been confirmed.

Two studies have estimated that 13 per cent of schizophrenia could be averted if all cannabis use were prevented. One suggested 50 per cent of the most serious cases would be avoided.

Read more: Rethink's Cannabis Campaign

Cannabis / Marijuana Linked to Significant Increases in a Person's Risk for Schizophrenia


Have there been any studies showing a causal link between canabis and schizophrenia, such that without using canabis the schizophrenia would not have happened? I'm asking because it seems like correlational and ecological data could be explained by the possibility that teenagers experiencing the prodromal symptoms of schizophrenia are more likely to use canabis to self-medicate.

Posted by: Erin at March 23, 2007 06:55 AM

Yes - there have been studies that show a causal link between canabis and schizophrenia. One I know of is the one that showed people who had a certain gene (COMT) and who smoked canabis - developed schizophrenia at a rate that is 10 times higher than people who had the gene and did not smoke cannabis. So - in this study you have two groups of people with the same gene - one group who didn't smoke cannabis, one who did and the people who did developed schizophrenia at a 10 Times Higher Rate.

You can see the story on it here:

Schizophrenia Genes and Cannabis

Also - if you look at the link above that says "Cannabis / Marijuana Linked to Significant Increases in Person's Risk of Schizophrenia" - you'll see that there are literally several dozen studies on this topic. I encourage you to review them.

Posted by: szadmin at March 23, 2007 07:48 AM

Very interesting. Thank you!

Posted by: Erin at March 23, 2007 08:19 AM

I think you'll find that COMT research was not much more than a con job.
To get the association the researchers wanted they had to take out all indigenous people from the NZ study which had previously shown no causal relationship between cannabis use and schizophrenia.
They also relied on an Israeli paper I believe and had to remove the data from the arab participants before they got the result they wanted there too.
The paper has been questioned already amongst researchers as has the COMT genes significance at all unfortunately this has not been reported.
It is also worth noting that none of the research regarding cannabis has found it can cause schizophrenia it merely that symptoms that considered schizoidal(?) have been noticed.

Posted by: andy at March 23, 2007 10:05 AM

I was reading this article and i came across a paragraph where it had said "We now know that cannabis can be a trigger for mental health problems and smoking it under the age of 18 can double people's chances of developing psychosis." so what im asking is what the difference is, if they smoke the marijuana under the age of 18 whats going to be the difference? I mean i can understand it like when 14 year olds smoke it but what about like 16-18 year olds how would it make a difference if your in the 16-18 year old range?

Posted by: Trey at March 29, 2007 12:49 PM

The younger we are, the more rapidly our brains are developing. We go through a period of time during adolescence when nerve connections in our brain are "pruned" - rearranged, organized, and superfluous ones discarded. This is a very vulnerable period of time even without drugs. Some studies have shown that in some sub-populations of patients with schizophrenia, there is evidence of "too much pruning" resulting in decreased brain mass, and fewer connections.

The exact age range varies some by individual, but that brain maturation actually persists to a lesser degree even into our early twenties.

Even alcohol has been found to damage/disrupt brains more severely in the under-25 age range, than in the over-25 group (I am recalling this from memory, so forgive me for not being able to state the particular study), and the younger it is used the worse the damaging effects are, especially as you go below the age of 21.

The way cannabis may trigger some cases of schizophrenia is very different from alcohol, as far as I know - I am just bringing up how the brain itself (physically) reacts differently at a younger age. Even our emotional responses change - What may be stress and a trigger at one age may not be when we are older and more mature.


Posted by: Jeanie at April 4, 2007 07:52 AM

You might be interested in this article:

Just As You Suspected, Teen Brains Are Not Fully Developed

( )

Posted by: Jeanie at April 10, 2007 06:36 AM

The glutamate hypothesis, there is the link between the NMDA receptor hypofunction and schizophrenia. The goal of my comment is to show that cannabis use can be a proof about this "NMDA link". See my website , chapter; Hyperfunction (Alzheimer’s disease and Parkinson disease) and hypofunction (schizophrenia) of glutamatergic neurons. See also my opinion- articles in Medical News Today and I think that marijuana is a serious problem, because according to the science studies it seems that cannabis use can precipitate schizophrenia in vulnerable individuals (alkoholism, undernutrition…), especially. However, there are other studies about the opposite marijuana effect, so scientists say; „One possibility is that there are good guys and bad guys within cannabis… Maybe the cannabidiol ameliorates some of the effects of the THC and maybe it actually might be good for you if you are psychotic“. I would like to show that there can be a "nutritional theory" (different „body calcium status“ in good and bad guys…) about the cause of schizophrenia based on "calcium deficiency"...

Posted by: Josef Hlasny at September 5, 2007 04:39 AM

Thanks for a beautiful site! I have added you in elected!
Necessarily I shall advise your site to the friends!

Posted by: Lohness at June 16, 2008 08:24 PM

Post a comment

Please enter this code to enable your comment -
Remember Me?
(you may use HTML tags for style)
* indicates required