Thursday, November 20, 2008

Marijuana and Dementia

Over the years there have been multiple studies indicating the potential of cannabinoids across a wide range of conditions. This latest study provides further weight as to the therapeutic potential of cannabinoids. It is high time that the public was made aware of the considerable therapeutic potential of these compounds. As for the psychosis\schizophrenia risk, that has been too much overblown and the risk is virtually negligible post 21 years of age. The reasons for this therapeutic potential are:

  • The two principal cannabinoids, THC and cannabidiol, have very strong antioxidant capacity.
  • These two compounds are lipophilic, that is lipid soluble, hence will remain in the body for extended periods. For pot smokers, typical wash out periods are 90% after one week, though this can greatly vary.
  • Both of these compounds target specific receptors. THC will target CB1 and to a lesser extent CB2(controversial), while cannabidiol is very specific for CB2 and hence is non-psychoactive.
  • Both compounds will bind to the anion site of ACHe, an enzyme that breaks down acetylcholine. This neurotransmitter is markedly reduced in some dementias, particularly Alzheimers.
  • ACHe is also strongly implicated in amyloid production, both cannabinoids reduce the production of amyloid, an early step in Alzheimers because this production seems contingent on the anion site.
  • Activation of the CB2 receptor limits the expression of pro-inflammatory cytokines, excess production of these cytokines being implicated in everything from atherosclerosis to cancer to dementia.


Francis Xavier Holden said...

John - I'd be keen to see the cites for psychosis\schizophrenia risk post 21 or any pointers.

John said...


Yeah, just open that can of worms for me!

There is little value in me pointing you to specific sources and references because these are all over the net and it can easily degenerate into cherry picking the data. Accordingly I will state my opinion and if you wish to spend several months trying to penetrate the veritable mountain range of literature on the subject then be warning such an undertaking may well drive you insane.

My personal view goes like this:

Persistent smoking in adolescence is a risk factor but in the vast majority of cases only for those so predisposed.

Post 21 years of age the risk becomes extremely small and in my view is negligible; particularly when we consider that migration, psychosocial stress, and unemployment are also risk factors.

If marijuana is a large risk factor for schizophrenia(there are many risk factors) then we should not need subtle statistical analyses to demonstrate the relationship. It should be obvious simply be comparing rates of schizophrenia relative to cannabis consumption across various countries. Yet the evidence is that rates of schizophrenia remain remarkably consistent, one reason why many researchers are of the opinion that the risk very much applies to those so predisposed to schizophrenia. There should also be variable rates of schizophrenia diagnosis in relation to changing rates of cannabis consumption.

The diagnosis of psychosis and schizophrenia remains problematic. In relation to schizophrenia I do not even consider this to be a single entity pathology, it probably is an umbrella diagnosis. For an entertaining view of the diagnostic problem google: "David Rosenhan" and "Thomas Szasz"

As to how one can determine those "at risk" is beyond me but I suspect a certain amount of creative guessing is going on here.

Publication bias exists. If a researcher wants to make a media announcement to the effect: yes there is a small risk but don't worry too much about it, as opposed to: it is a bloody big problem and we had better do something about it, guess which ones get the ears of the public and politicians.

A number of mental health professionals I have spoken too appear to have a rather casual attitude towards marijuana consumption. That is, while not downplaying the potential risks, they do not seem overly concerned by it. This is in stark contrast to the media savvy types who know the value of a good sound byte to promote their funding opportunities.

My typical advice to teenagers is not "don't smoke" because "saying no" doesn't work. Rather it is to caution them against a continual habit because it does impact on schooling and can lead to self medication for mood problems which in my view is quite dangerous. Despite what many say I do believe marijuana can be addictive(caveat: "addictive drug" is a dangerous concept, one man's meat is another man's poison).

Look at the USA, a recent analysis found that while it is has the most stringent anti-drug laws it also has the highest rates of illicit drug use.

While marijuana consumption by teens in Australia has declined markedly over the last few years, rates of alcohol, amphetamine, and ecstasy abuse have sharply risen. Out of the frying pan into the fire. Amphetamines definitely do cause considerable brain damage, as does binge drinking, now recognised as a serious problem here in Aus. Ironically, all the evidence suggests that cannabinoids are potent neuroprotectants and as such probably would help prevent the damage arising from amphetamines and alcohol.

To summarise:

If people are concerned about the risk of marijuana and schizophrenia for adults then they should be much more concerned about mental health risks associated with sustained unemployment, psychosocial stress, and regular alcohol consumption.

Francis Xavier Holden said...

Thanks for that effort.

It roughly states my view. Sorry I mean I would put my view, which is much the same, much less articulately.

You'll have to come over to Harry Clrakes place some time and help us educate Harry

John said...

Hey Francis,

You mean this Harry Clarke?

I have read his comments and visit his blog periodically. The ruckus concerns the marijuana - psychosis link appears to have convinced many of its dangers. I'm not sure that people like Harry will be easily deterred from their view and I'm somewhat tired of blogger battlegrounds.

What needs to be pointed out to the likes of Harry are the following:

1. Schizophrenia is definitely associated with cerebral pathology. Sometimes subtle but it is very often there and tends to increase with illness duration. Yet there are a veritable mountain of studies showing cannabinoids are potent neuroprotective properties.

2. Harry needs to be educated re the experiments of Rosenhan and Szasz.

3. Harry is a good bloke, I'm sure he means well, but I also suspect that when so many authority figures are saying its bad Harry he will accept their judgment over mine.

4. You can ask Harry this simple question: Why are all the potential therapeutic possibilities of cannabinoids, from delaying atherosclerosis to killing brain tumours to preventing amyloid aggregation, not be made public in Australia and this in spite of the fact that very substantial data on this effects have been available for over a decade?


If the subject comes up again, comment here, any post will do as I receive email notification of posts, and I'll see what I can do.

Francis Xavier Holden said...

John - yes that is Harry -I think he has done some great work on the economics of drugs, alcohol and tobacco.

todd said...

sorry - my message is off topic - i would like to ask you a question about your post on the MBTI over at if i can. please let me know if this would be alright with you. thanks.

John said...

Go for it Todd, I happen to know quite a bit about MTBI.

todd said...

okay - thank you for your willingness. (again sorry for being off-topic.) You state that the MBTI "is everywhere in business but psychologists laugh at it unless of course they are organisational psychologists." You seem to be implying that organisational psychologists are somehow of a lower grade of psychologist? (I have no opinion on that, but I personally know a psychologist who has administered the MMPI in the past. He has a PhD and isn't an organizational psychologist. Is he using rubbish when he uses the MMPI to assess his patients?) I guess I would ask of MBTI detractors: can you point out one failure among those who promote it? thousands of university professionals can't be wrong, can they? and would they keep using it to administer to students if it weren't working?

John said...

I'm implying that the Myers Briggs is a favourite tool of org. psychs because most people like those self exploratory tests and it makes for good conversation. Whether or not Myers Briggs actually contributes to how an individual works is another question. For the org psych the test results will provide an image of the person but there isn't a great deal of information in each individual image. Where the information becomes useful is when within any organisation there emerges a pattern of types under that image that suggest something about the culture and recruiting habits of the organisation. Taken together with other test results, MB may be able to provide useful information for an organisation, but whether or not it is actually explaining anything about individual human behavior is an entirely different question

For org psychs MB is useful because it is quick and non-technical. Org Psychs don't have time or resources for the more subtle, time consuming and expensive tests. Even if they did I'm not sure how much useful information they would glean out of these procedures. The big problem for org. psychs is the inherent lack of precision in their tools.

At present this lack of precision is unavoidable, it merely represents the current state of knowledge and all too often misinformation. We are very much at sea here, a fact driven home to me by two individuals working in very different areas of psychology. What they impressed upon me is that for all our talk about the causes of human behavior all too often we are attempting explanations at the wrong level of analysis or are merely engaging in describing, not explaining behavior.

Personality tests do not explain causes of behavior rather these are just another description of behavior. We need a different way to approach these issues. For example, to say that someone likes to work alone rather than spend time with people because that someone is an introvert is to engage in circular reasoning. In relation to the prior example, one crude attempt could go like this: strong introverts are not just socially less active than others but more stimulus sensitive than others. There are even studies indicating that strong introverts have a heightened sense of internal awareness(what is going on in their bodies) than others. It has been speculated that strong introverts have less inhibitory tone in the reticular formation, thereby allowing more information to reach the higher cortical areas. They prefer low external stimulus environments because relative to others than brains are already processing a lot of information. Which may also help explain why strong introversion is also associated with creativity.

We should not be that surprised that unproven practices still hold sway. Just last year an Australian study found that a 150 year old procedure during surgery was not only useless but possibly dangerous. Many psychologists still talk about self esteem but the data on that is shot. After all, psychopaths and bullies have high self esteem. When I read studies on creativity there was the hint that self doubt and criticism seemed very important. While there is no empirical data to support the self esteem concept, in fact the data suggests otherwise, the concept of self esteem is very prevalent in psychology.

The most successful therapies involve direct interaction with behavior. Psychology and Psychiatry have a long history of chasing ghosts, it is quite remarkable how hard we have to work to change our fundamental view of ourselves.

Thousands of university professors can be wrong. In fact we can take it as a given that at any point in time there are thousands of professors making incorrect claims. Psychology, as a science, is only in becoming. We should be surprised at our ignorance because Psychology is about the study of the most complex processes in the known universe: human behavior.

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viagra online said...

Id like to know if although dementia is far more common in the geriatric population, it may occur in any stage of adulthood.

John said...

There is early onset dementia, this can happen even in the 40's but the condition is not common. Some types of brain injury can increase the risk of early onset dementia. Google, "chronic traumatic encephalopathy" for a prominent example.

Buddhist Monkey said...

The more I read your words, the more infatuated I become! People such as yourself (i.e., smart, funny, elloquent, educated, insightful, concise, entertaining, eccentric; all of which I rate highly as sought-after personal attributes) are few and far between. Do you have a Bio posted somewhere? I want to know more about you.
NB: At the risk of patronising your learned self, may I suggest meditation as an amazing tool with which to combat insomnia? I'd be happy to share some techniques if you're interested.

John said...

Buddhist Monkey,

Thanks for the kind words.

Yeah I'm one of the outliers. Happy being that way, can't imagine myself being any other way, can't even imagine myself for that matter. Well I can but it is an image. As Camus wrote in the Myth of Sispyphus, "Forever shall I be a stranger to myself." Or as the poet Walt Whitman stated: there are as many selves of me as people who know me. I don't know, in these days it is all so strange and wonderful.

Insomnia has long been with me. I found a Hindu meditation trick useful. Just listen to whatever sound you can hear, focus on that. It stops the inner chatter. I just sort of drop off to sleep. Another one is to focus attention right in the middle of the forehead, just think about that spot.

Lots of interesting studies on meditation, everything from improving mood to improving immune function.

Thanks again,


I've added a few pieces to the bio but it won't help much. Honestly, I really have a lot of trouble with the idea of "who I am?"

Ash said...


I thought you might be interested to know (if you haven't already heard) that the latest is that marijuana doesn't appear to be effective in treating Alzheimer's disease -

Interesting because the arguments in your article are logical and previous studies were leaning in favour of it being possible.