Schizophrenia and Cannabis ” A review, Part 1

by Doctor X

The supposed link between smoking cannabis and developing schizophrenia is frequently championed by members of the government, media, and parents and teachers everywhere.” But, like so many things proclaimed by these often ill-informed groups, the current state of research would indicate that the issue is much more complex than it superficially appears.

Firstly, it is important to define exactly what we mean when we are discussing the term schizophrenia in the context of cannabis use.” Many regular smokers, or acquaintances of smokers will no doubt have heard of people “flipping out” when very stoned, often requiring a prompt trip to the emergency department.” However, the delusions, weird thought processes and disconnection from reality in these cases of “toxic” recreational use are examples of a drug-induced psychosis, NOT schizophrenia.

Almost all individuals who have smoked themselves to the point of an acute psychotic event will completely return to normal (over a few weeks) when they cease smoking, which they usually do for some time after one of these episodes as they are particularly unpleasant for all concerned.

Drug induced “toxic” psychoses are by no means limited to cannabis, and can be caused by most recreational drugs in high enough doses, particularly amphetamines, but even alcohol can cause them in sufficient quantity.

Schizophrenia on the other hand, refers to a complex set of symptoms that have to be present for at least 6 months (continuously) before a formal diagnosis can be made.” These symptoms are grouped into “positive” and “negative” categories, depending on their nature.” For example, auditory hallucinations (“everybody hates you”), delusional thoughts (“they are implanting ideas in my brain”) and extreme paranoia are positive symptoms.

Withdrawal from social interaction, disregarding personal hygiene (looking like a hobo) and employment, and a “flat” or “blunted” personality are examples of negative symptoms.” Interestingly, the negative symptoms are far more common than positive, despite what is portrayed in the media.

In general, the main risks for developing schizophrenia are being young (under 30), male, poor and having a blood relative with a psychotic disorder (of which there are many, not just schizophrenia).” Unfortunately, this brings us to one of the main complexities of the issue, as the “risk factors” for getting a good level of cannabis use going also happen to be being young, male, poor and having a family member who has a substance use issue.

This generally means that the onset of schizophrenia symptoms and the onset of cannabis use dovetail at a similar age.” This makes it very difficult to tease out the causality of the two (i.e. which came first).” Did the 18 year old Johnny start smoking cannabis and then develop schizophrenia as a result, or did he become symptomatic for schizophrenia, and started smoking cannabis after this?

There are a few key issues that confound most studies into the relationship between mental illness and cannabis use.” A primary issue is that THC is a controlled substance, which makes reliable data very difficult to obtain.” This is because most information regarding levels of use, time of symptom onset and other drug use is obtained retrospectively, or from “self reporting” by users. As most patients presenting with psychosis are not the most reliable witnesses, (and they are usually high) this throws some spanners into the data collection works.

Another of these factors is that, anecdotally, patients with a diagnosis of schizophrenia often report a reduction in the symptoms of their illness when smoking cannabis.” Therefore, lots of schizophrenics smoke cannabis.” Therefore (so the argument goes) schizophrenia is cause by smoking cannabis.

I hope we can all see the error in this.” This is what is known as correlation, not causation.” It is similar to saying that global warming is a result of the reduced number of pirates over the last century.” There sure are a lot less pirates around, and the world sure is getting hotter, and this all happened over a similar time period.” Conclusion: we must reinstate more pirates in an attempt to curb global warming.” Given this anecdotal evidence, it would almost seem that rather than actively causing schizophrenia, patients are in fact self-medicating with cannabis as result of their illness.

Polysubstance abuse is another factor that further muddies the water.” This is because a significant number of patients who develop schizophrenia are not just smoking pot.” Anecdotally (again), it would appear that a large number of individuals who present with symptoms of schizophrenia are taking a combination of recreational (and prescription) drugs on top of their cannabis use.

So, is it the $50 bag a day that Johnny smokes, or the 3g of IV speed as well, or the four e”s he has, or the six beers he washes it down with, or is it all of them together, or none at all”? As you can see, it is effectively impossible to tease apart a direct, single drug link in these cases of polysubstance use.” However, on the basis of my experience, it is the combination of amphetamines and THC that is the single likeliest combination to induce a toxic psychosis (not schizophrenia), so my advice is to not mix the two if possible.

Very interestingly, a current research paper has tentatively found that there does not appear to be a link between the specific symptoms of schizophrenia and the choice of abused drug, rather, the choice of the abused drug depends on what is being used in the surrounding social community.” Unfortunately though, this is a single study with a small group of people, so it is by no means definitive (which is a theme you will notice amongst the current research) in its conclusions.

Hopefully, I have managed to give a broad picture as to why it is so difficult to effectively study the link between cannabis (or any drug) and mental illness.” This is a mere glance at the topic however and in the next instalment, I will give an overview of what the current research indicates, and address the issue as to whether a “normal” person smoking cannabis has an increased risk of developing schizophrenia (which is really what you wanted to know, isn”t it).

Doctor X is a medical doctor working in the ACT. He wishes to remain anonymous – Ed.

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