by Stefanie on 23/09/2015 | Opinion

Cannabis does not make your brain smaller

brain The advocators of a ban on cannabis would have us believe that even incidental use causes the brain to shrink, and that it causes psychoses or schizophrenia. The rumours about the brain shrinking stem back to this study in 2014, on which various sensational news reports are based. The study is not, however, a longitudinal study, but rather represents a snapshot study of a limited number of test subjects.


Facts versus fiction

The advocators of a ban on cannabis would have us believe that even incidental use causes the brain to shrink, and that it causes psychoses or schizophrenia. The rumours about the brain shrinking stem back to this study in 2014, on which various sensational news reports are based. The study is not, however, a longitudinal study, but rather represents a snapshot study of a limited number of test subjects. The researchers themselves assert that age of first use is much more important and that their results do not point to a single conclusion.

Research into cannabis use and intellectual performance

Early this year, the University of Colorado Boulder published a study that proves the opposite: cannabis use does not cause the brain to shrink. Two new studies now support these findings.  The most recent study was published in August 2015 in JAMA Psychiatry and studied the impact of cannabis on certain areas of the brain in over 1500 test subjects. This research confirms the findings of the reputable Harvard University from 2013: cannabis use does not have any impact on the size of the brain.

In the Harvard study, 22 heavy users of cannabis, who in total had smoked an average 20,100 bags of cannabis in their lives, were compared to 26 non-smokers of cannabis. No differences were observed between the two groups with regard to the volume of the white matter of the brain, the cerebrospinal fluid, or the left or right hippocampus. The authors concluded that “these findings are in line with the latest literature with regards to the fact that there is no link between cannabis use and structural changes in the brain as a whole or in the hippocampus.”

Researchers of Duke University in Durham/North Carolina followed 1,037 participants from New Zealand from their birth in 1972/73. Throughout their lives they were examined and questioned at regular interviews. Published in 2012, the study is to this day the most significant research into the link between cannabis use and intellectual performance. One of the research heads, Terrie Moffit, professor of psychiatry at King’s College London, commented to the BBC: “It is such a special study that I’m fairly confident that cannabis is safe for over-18 brains, but risky for under-18 brains.” The results of this study were somewhat lost here [in Germany] amidst the news that cannabis is damaging for children and young people. ‘Stupid potheads’ became a buzz word in the national and international media. The key result of the study – that cannabis is safe for adults, but not for adolescents – went largely noticed. Even the left-wing newspaper taz.de reported that “smoking pot makes you stupid”.

Does smoking cannabis make you schizophrenic?

Schizophrenia is the second argument used by objectors to prevent a regulation that deals with the drug rationally. JAMA Psychiatry also recently published on this subject, stating that young men in particular should not, or only very rarely, smoke cannabis to prevent harm to the development of the brain. The research demonstrates that men who smoke cannabis regularly at a young age run the risk of harming the development of the brain, which can negatively impact the thickness of the cerebral cortex. Whether, and to what extent the development of the cerebral cortex is linked to the development of schizophrenia is disputed by researchers. In this case too, this applies to children and adolescents; the effect could not be demonstrated in adults.

In 2014, the well-reputed Harvard Medical School published a study in which they concluded that schizophrenia is a hereditary illness, and is not linked to the use of cannabis. The research concluded that “in summary, we conclude that cannabis does not cause psychosis by itself.”  In genetically vulnerable individuals, cannabis can impact the onset, severity and outcome of the illness. More research is therefore needed in this regard. What is clear, though, is that cannabis use is not the cause of the illness. This view is shared by the authors of the latest study, which was published early August 2015. In their results they state that “teen marijuana use by adolescents is not linked to psychoses, cancer or other health problems.”

One of the few German cannabinoid experts, Dr. Franjo Grotenhermen, confirms this fact in the Huffington Post: “There are no indications that cannabis causes damage to adults. The fully grown brain is not damaged.”

A lot of research has been carried out into cannabis, but no-one is interested

When it comes to cannabis it would seem that for every study there is another study that contradicts it, giving legislators extra time before they are compelled to take action. Nonetheless, there is a relatively large body of research into cannabis. Medically speaking, it is even one of the most thoroughly researched plants. According to the trade journal Medicinal Research Reviews, in 2008 alone, there were more than 15,000 studies in the field of cannabis and cannabinoids. According to Paul Armentano, director of NORML, that same statistic was higher than 20,000 in 2010.

Nonetheless, after admittance in Canada, it took another six years and plenty of additional research before Sativex, a cannabis spray for MS patients, was also permitted in Germany in 2011. In Germany, the Bedrocan cannabis issued by pharmacies must comply with strict rules. In the Netherlands – unlike in Germany – it has been officially recognised as medicine for years. For this reason even Dronabinol, the first German cannabis medicine, has a special status as prescriptive medicine and twenty years after its introduction, the brand still isn’t recognised as a true medicine there. Those politicians and healthcare professionals responsible regularly argue that there are a lack of clinical trials. This is simply an excuse. Between 2005 and 2009, 37 controlled studies were carried out in to the use of cannabinoids for therapeutic purposes. Nine of these studies demonstrate reduction in spasms in sufferers of MS; four demonstrate a positive impact on symptoms and appetite in sufferers of HIV/AIDS. Four other studies demonstrate chronic pain relief and two others demonstrate the impact of cannabis on intestinal disorders. In addition, there are two studies into the use of cannabis for nausea and vomiting, two about cannabis and schizophrenia, one about glaucoma, and two about other illnesses. Since then, the number of studies in the context of the regulation models has increased by more than 100. Many of these studies demonstrate the medicinal effectiveness of the cannabis plant or cannabis preparations, but in Europe these are largely ignored. A double-blind study into cannabis for neuropathy performed in California produced promising results. For this illness, the researchers consider cannabis to be very effective medication with few side effects. In addition, a fairly recent study in Germany into the effect of cannabis as a means of limiting tumour cell reproduction and the impact of CBD on Alzheimer’s attracted a lot of attention among medical experts in the US. In Germany, meanwhile, most doctors are still stuck on whether you can prescribe a terminal cancer patient THC drops without this causing problems with insurance companies. We are talking about a medicine which, 70 years ago, was available in every German pharmacy and did not result in the problems, and even deaths, caused by other medicines.

Cannabis cures increasing numbers of people

Cannabis is by no means a miracle cure, but it would seem that more people than ever are benefiting from it. In Germany itself, very little research has been done and results from other countries are ignored. The result of this should be that the strict regulations are abolished as soon as possible, and not just for medicinal cannabis. We do not need even more studies into teen potheads to make clear that weed should not end up in the hands of children and adolescents. What we need is clear legislation to regulate cannabis, without doomsday scenarios about children and adolescents. But the Federal Government of Germany will not cooperate, as was recently reiterated by Marlene Mortler, who is responsible for the German drugs policy.

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