Monthly Archives: July 2013

Cannabis and psychosis: Have we found the missing links?

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The association between cannabis and psychosis has long been a matter of debate, with cannabis widely perceived as a harmless recreational drug.

Heavy cannabis use at a n young age, in association with genetic liability to psychosis and exposure to environmental stressors like childhood trauma and urban upbringing increases the risk of psychotic outcome in later life.

Cannabis acts as a component cause of psychosis, that is, it increases the risk of psychosis in people with certain genetic or environmental vulnerabilities, though by itself, it is neither a sufficient nor a necessary cause of psychosis.”

http://www.ncbi.nlm.nih.gov/pubmed/23810133

Cannabis use does not cause schizophrenia

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“According to a new report by a British government advisory body, the regular use of cannabis though it can have real and significant mental health effects it is unlikely to cause schizophrenia.

The Advisory Council on the Misuse of Drugs says that based on current evidence smoking cannabis was likely to increase the chances of developing schizophrenia by just one per cent.”

More: http://www.news-medical.net/news/2006/01/24/15577.aspx

Marijuana’s Link to Schizophrenia Debated – American News report

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“With the growing use of medical marijuana to treat chronic pain and other health problems, the debate over the medical effects of the drug on the human mind continue to make their way through the medical community.

The latest salvo comes from researchers in Australia and England.  At the center of the debate is the possible relationship between marijuana (cannabis) and mental illnesses such as schizophrenia.

Castle cites one study that indicated people with schizophrenia had a lifetime rate of cannabis exposure of 97 percent – meaning almost all of them have tried the drug.  Yet, he also notes that most people who use cannabis do not develop schizophrenia, and that many people diagnosed with schizophrenia have never used cannabis.

“Therefore, it is likely that cannabis exposure is a ‘component cause’ that interacts with other factors to ‘cause’ schizophrenia or other psychotic disorders, but is neither necessary nor sufficient to do so alone,” Castle wrote.

However, the authors of the accompanying article are not as convinced that the prevailing scientific evidence proves a relationship exists between pot use and schizophrenia.”

More: http://americannewsreport.com/marijuanas-link-to-schizophrenia-debated-8817482

A false link between marijuana and mental illness

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“The article published today in “Health News” makes the claim that smoking marijuana is “linked” to early onset of mental illness.

However, although the article implies some sort of cause and effect, that conclusion has no scientific basis. In fact, the authors of the study don’t even bother investigating whether marijuana use causes mental illness or if people with mental illness have a higher rate of smoking marijuana than the general public.

If marijuana caused mental illness, then cultures that have a higher rate of marijuana smoking than the U.S. should have a higher rate of mental illness. But in fact, the opposite is true. Cultures with higher rates of marijuana consumption have lower rates of mental illness than the United States. This would indicate that rather than marijuana causing mental illness, as your article implies, it is people with mental illness who are self medicating with marijuana in order to alleviate their symptoms.

This (more correct) reading of the data, however, does not fit the narrative being presented by the politicians who are making their careers by “getting tough” on marijuana smokers, nor does it fit the narrative of the manufacturers of the currently legal psychotropic drugs, like Prozac and Zoloft, who stand to lose billions of dollars if medical marijuana is legalized, and who funnel millions of dollars to those politicians who present their dubious science as fact.

Had your newspaper even taken the time to Google the Archive of General Psychiatry, you would have found that the “study” you cited was conducted by the “Genetic Risk and Outcome in Psychosis (GROUP) Investigators,” who publish only articles against medical marijuana. That alone should raise a red flag to anyone with a basic understanding of scientific research. When someone conducts numerous studies and publishes many articles that all draw the same conclusion, whether the evidence leads to that conclusion or not, the critical eye should suspect some ulterior motive at work. It’s not possible to keep an open mind when you have an axe to grind.”

William Smith, Baltimore

http://articles.baltimoresun.com/2011-02-09/news/bs-ed-marijuana-letter-20110209_1_mental-illness-medical-marijuana-lower-rates

Doubt cast on cannabis, schizophrenia link – ABC Science

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“A new study in the UK has cast doubt on the supposed link between cannabis use and schizophrenia.

This latest study, led by Dr Martin Frisher of Keele University, examined the records of 600,000 patients aged between 16 and 44, but failed to find a similar link.

“An important limitation of many studies is that they have failed to distinguish the direction of association between cannabis use and psychosis,” the authors write in the latest edition of the journal Schizophrenia Research.

Not as predicted

Frisher and colleagues compared the trends of cannabis use with general practitioner records of schizophrenia.

They argue if cannabis use does cause schizophrenia, then an increase in cannabis use should be followed by an increase in the incidence of schizophrenia.

According to the study, cannabis use in the UK between 1972 and 2002 has increased four-fold in the general population, and 18-fold among under-18s.

Based on the literature supporting the link, the authors argue that this should be followed by an increase in schizophrenia incidence of 29% between 1990 and 2010.

But the researchers found no increase in the diagnosis of schizophrenia or other psychotic disorders during that period. In fact some of the data suggested the incidence of these conditions had decreased.

“This study does not therefore support the specific causal link between cannabis use and the incidence of psychotic disorders,” the authors say”

http://www.abc.net.au/science/articles/2009/09/01/2673334.htm

Cannabis/schizophrenia link questioned

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“The Swiss government is questioning the results of a study showing a link between marijuana use and schizophrenia.

The Zurich University study showed a higher incidence of schizophrenia in the 1990s in the age groups most likely to use cannabis, Swissinfo said Wednesday.

“We know from other experimental studies that cannabis can cause psychosis, but we have now established a clear link to schizophrenia for the first time,” study co-author Wulf Rossler said.

Swissinfo said the Federal Health Office is questioning the report, saying the patients’ drug histories and other medical details remained unknown.

“It does not uncover the medical history of the patients, for instance the consumption of psychotic substances or other factors that could lead to psychotic illnesses,” the health office in a statement.”

http://phys.org/news104659898.html

Minimal Relationship Between Cannabis And Schizophrenia Or Psychosis Suggested By New UK Study

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“Last year the UK government reclassified cannabis from a class C to a class B drug, partly out of concerns that cannabis, especially the more potent varieties, may increase the risk of schizophrenia in young people. But the evidence for the relationship between cannabis and schizophrenia or psychosis remains controversial. A new study has determined that it may be necessary to stop thousands of cannabis users in order to prevent a single case of schizophrenia.

Scientists from Bristol, Cambridge and the London School of Hygiene and Tropical Medicine took the latest information on numbers of cannabis users, the risk of developing schizophrenia, and the risk that cannabis use causes schizophrenia to estimate how many cannabis users may need to be stopped to prevent one case of schizophrenia. The study found it would be necessary to stop 2800 heavy cannabis users in young men and over 5000 heavy cannabis users in young women to prevent a single case of schizophrenia. Among light cannabis users, those numbers rise to over 10,000 young men and nearly 30,000 young women to prevent one case of schizophrenia.

That’s just part of the story. Interventions to prevent cannabis use typically do not succeed for every person who is treated. Depending on how effective an intervention is at preventing cannabis use, it would be necessary to treat even higher numbers of users to achieve the thousands of successful results necessary to prevent a very few cases of schizophrenia.

Matt Hickman, one of the authors of the report published last week in the scholarly journal Addiction, said that “preventing cannabis use is important for many reasons – including reducing tobacco and drug dependence and improving school performance. But our evidence suggests that focusing on schizophrenia may have been misguided. Our research cannot resolve the question whether cannabis causes schizophrenia, but does show that many people need to give up cannabis in order to have an impact on the number of people with schizophrenia. The likely impact of re-classifying cannabis in the UK on schizophrenia or psychosis incidence is very uncertain.”

Source:
Amy Molnar
Wiley-Blackwell”

http://www.medicalnewstoday.com/releases/168519.php

Alcohol and cannabis use and mortality in people with schizophrenia and related psychotic disorders.

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“The impact of co-morbid substance use on mortality is not well studied in psychotic disorders. The objective of this study was to examine the impact of substance use on mortality in people with psychotic disorders and alcohol and/or drug use.

…In a Cox model, predicted mortality risk was higher in age group 35-55 compared to <35 years and in males, but reduced in cannabis users. Overall five- (3.1% vs 7.5%) and ten-year mortality risk (5.5% vs. 13.6%) was lower in cannabis users than in non-users with psychotic disorders (p = 0.005) in a survival model.

 We observed a lower mortality risk in cannabis-using psychotic disorder patients compared to cannabis non-users despite subjects having similar symptoms and treatments.

 Future research is warranted to replicate these findings and to shed light on the anti-inflammatory properties of the endocannabinoid system and its role in decreased mortality in people with psychotic disorders.”

http://www.ncbi.nlm.nih.gov/pubmed/22595870

Cannabinoids and Schizophrenia: Therapeutic Prospects.

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“Approximately one third of patients diagnosed with schizophrenia do not achieve adequate symptom control with standard antipsychotic drugs (APs).

The endocannabinoid system (ECS) in the brain plays an important role in maintaining normal mental health.

ECS modulates emotion, reward processing, sleep regulation, aversive memory extinction and HPA axis regulation…

The cannabis plant synthesises a large number of pharmacologically active compounds unique to it known as phytocannabinoids. In contrast to the euphoric and pro-psychotic effects of delta-9-tetrahydrocannabinol (THC), certain non-intoxicating phytocannabinoids have emerged in pre-clinical and clinical models as potential APs.

Since the likely mechanism of action does not rely upon dopamine D2 receptor antagonism, synergistic combinations with existing APs are plausible.

The anti-inflammatory and immunomodulatory effects of the non-intoxicating phytocannabinoid cannabidiol (CBD) are well established and are summarised below.

Preliminary data reviewed in this paper suggest that CBD in combination with a CB1 receptor neutral antagonist could not only augment the effects of standard APs but also target the metabolic, inflammatory and stress-related components of the schizophrenia phenotype.”

http://www.ncbi.nlm.nih.gov/pubmed/23829368

“6”-Azidohex-2″-yne-cannabidiol: a potential neutral, competitive cannabinoid CB1 receptor antagonist… 6″-azidohex-2″-yne-cannabidiol was as potent as cannabidiol in producing surmountable antagonism… it is a competitive cannabinoid CB(1) receptor antagonist…it may be a neutral cannabinoid CB(1) receptor antagonist.”  http://www.ncbi.nlm.nih.gov/pubmed/15033394