This post discusses work published January 24th 2017 in the Journal of Molecular Psychiatry titled "Cannabis use and risk of schizophrenia: a Mendelian randomization study."

---

Preface

Full disclosure, I am a supporter of legal, recreational use of marijuana as well as an increased focus on research into the potential medicinal uses of various canabanoids which can be extracted from this plant. The information contained within this article does not change my personal stances, however it is certainly worth noting.

The Proposed Link Between Marijuana Use and Schizophrenia Is Not New

There have been a wide variety of publications discussing a correlation between the use of marijuana and potential psychotic effects. (2), (3), (4).

These articles have all stressed the fact that correlation is not causation, and that the identification of a causal relationship between schizophrenia and marijuana usage was necessary for making health related recommendations. Were the relationship between cannabis use and schizophrenia causal, cannabis use would represent the most easily modifiable risk factor for development of psychological disorders.

The authors of these previous articles have noted that appropriate steps to account for reverse causation (meaning, those more likely to experience psychological episodes are more inclined to use cannabis rather than the other way around), bias, and other confounding variables were not always appropriately accounted for. As such no previous studies ever indicated a direct causal relationship. (2)

Those publications weren't holding Arnold back

Nevertheless, these publications

have consistently demonstrated that exposure to cannabis is associated with an increased risk of schizophrenia or related disorders.

In addition, there have been biochemical studies showing that certain canabanoids can interfere with various neurotransmission pathways. Interference with these pathways have also been implicated in the development of various psychological disorders, so secondarily there is an indicator that the aforementioned correlation does have a potential biochemical mechanism in the body. (5)

---

What Did The Authors Do?

In the newly published article, the authors utilized Mandelian randomization in order to explore whether or not there was actually a causal effect between cannabis exposure and elevated risk of schizophrenia.

Mandelian randomization is a way to get unbiased estimates of the effects of a potential causal variable without doing a traditional randomized trial. (7)

To achieve this the authors used 10 most common single-nucleotide polymorphisms (SNPs, pronounced "snips") from a genome wide analysis studying the genetic changes caused by cannabis use, published in 2014 in the Journal of Translational Psychiatry, in order to identify whether or not there was actually a causal link.

Wait what the hell is a SNP?

SNP's are the main source of genetic variation between people, they are the change of a single nucleotide (say a C in one person and an A in a different person). Many of these changes result in no changes to the sequence of proteins (remember that nucleic acids are organized in codons, three base sequence codes, which correspond to the inclusion of a specific amino acid component in a protein, we discussed that [Here] (https://steemit.com/science/@justtryme90/science-lesson-dna-part-3-how-does-the-cell-get-information-out-of-dna) so click if you want a refresher) from the genes in which the SNP is contained (due to the redundancies that are a part of our genetic code). However other times they do result in changes, and these changes can result in people being more or less susceptible to various disease states. Thus testing people for SNP's is becoming an ever expanding part of medical diagnostics (particularly when looking for root causes for cancer). SNP's can even result in changes that make certain drugs less effective in people, while completely effective in someone without the SNP.

Okay So They Used the 10 SNP's That Result From Cannabis Use And...

They compared them with the genes known to be associated with increased risk of schizophrenia found that there was a causal relationship between the genetic changes occurring from use of cannabis and the genes known to be associated with schizophrenia (P=0.007) which they translated into a 37% increase in the risk for developing schizophrenia for users of cannabis vs. non-users. (Before you get scared, the likelihood of developing schizophrenia is about 1%.. so that means for cannabis users the likelihood is about 1.37%).

The authors also tested whether SNP's associated with smoking also were involved in a causal relationship with schizophrenia development (as a control) however no relationship was found.

Limitations To This Study

The authors...

did not control for quantity, type, route of administration or indeed the age at exposure to cannabis.

additionally

the precise mechanisms explaining how some of the genetic markers under analysis alter cannabis use (or dependence) remain unknown.

So additional explanations as to WHY they observed this correlation could not be determined. That said neither of these limitations their determined correlation any less true.

Conclusion

The data reported by this study strongly supports the hypothesis that cannabis usage is causally related to the risk of developing schizophrenia.

My Two Cents

This is nothing to be overly concerned about, as with any aspect of life their is always a positive and negative aspect. Their is no such thing as a free lunch, and there is no action we can perform, food we can eat, chemical we can consume that will not have potential effects on our bodies. What is important is to know about the potential risks associated with our actions and activities and make an informed decision to do what we want (rather than just not knowing).

---

Sources

1. http://www.nature.com/mp/journal/vaop/ncurrent/full/mp2016252a.html
2. http://www.biologicalpsychiatryjournal.com/article/S0006-3223(15)00647-2/abstract
3. https://www.ncbi.nlm.nih.gov/pubmed/11185941
4. https://www.ncbi.nlm.nih.gov/pubmed/15871146
5. http://www.biologicalpsychiatryjournal.com/article/S0006-3223(16)00082-2/abstract
6. https://en.wikipedia.org/wiki/Mendelian_randomization
7. https://academic.oup.com/ije/article-lookup/doi/10.1093/ije/dyg070
8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4872459/
9. https://ghr.nlm.nih.gov/primer/genomicresearch/snp

All Non Cited Images Are From Pixabay.com and Available Under Creative Commons Licenses

Any Gifs Are From Giphy.com and Are Also Available for Use Under Creative Commons Licences

---

If you like my work, please consider giving me a follow: @justtryme90. I am a PhD holding biochemist with a love for science. My future science blog posts will cover a range of topics in the biology/chemistry fields.

Thank you for your continued support of my work! I appreciate all those who follow me (and those who don't too).