Two interesting follow ups to last weeks blog concerning the health advice issued by the Dept of health regarding drugs.

The first came from a reader who pointed me to the website run by the NHS: The effects of drugs which has this to say about cannabis:

Cannabis can cause anxiety, paranoia and loss of motivation. There’s evidence that cannabis use increases the risk of developing a psychotic illness, such as schizophrenia, and can cause a relapse in those with a pre-existing condition. Cannabis, like tobacco, can cause lung disease. Long-term or heavy use may cause cancer.

Now according to the information reviewed last week there is

inconsistent and mixed evidence for whether heavy, chronic cannabis use is associated with a persistent ‘amotivational syndrome’ characterised by social withdrawal and apathy

Regarding the evidence that cannabis use increases the risk of developing a psychotic illness, such as schizophrenia, we were told

evidence that early initiation and regular, heavy cannabis use is associated with a small but significantly increased risk of psychotic symptoms and disorders in later life

Which is not the sames as claiming in a general way that “There’s evidence that cannabis use increases the risk of developing a psychotic illness”, indeed now the NHS says there is a

complex association between cannabis use and schizophrenia – some evidence that use may exacerbate psychotic symptoms and is linked with relapse but it is unknown whether this is a universal risk or due to differences in individual vulnerability

And of course we were told that there is

no conclusive evidence that cannabis causes cancer

Now of course the link to tobacco is worth highlighting as the document last week makes clear:

Studies of the harms associated with cannabis use are limited by confounding as many users smoke tobacco as well as cannabis, or use tobacco as vehicle for smoking cannabis resin. Although tobacco smoke and cannabis smoke are known to contain a similar range of mutagens and carcinogens, actual exposure to these compounds may differ between tobacco and cannabis users in terms of the frequency and duration of use, and because of factors such as the depth of inhalation

Yet if you follow the link to the cancer information above we are told

Smoking cannabis has also been linked to an increased risk of lung cancer.

Which is a very dubious claim to make, given the abundance of research which does not

Most cannabis smokers mix their cannabis with tobacco, and although they tend to smoke less than tobacco smokers, they usually inhale more deeply and hold the smoke in their lungs for longer.

Interesting that they highlight the connection between cannabis and tobacco, but do not advise users to smoke pure cannabis.

One researcher has estimated that smoking four ‘joints’ (homemade cigarettes mixed with cannabis) may be as damaging to the lungs as smoking 20 cigarettes.

This is an amazing claim for the NHS to make – especially as they don’t even give any reference.

Even smoking cannabis without mixing it with tobacco is potentially dangerous. This is because cannabis also contains substances that can damage DNA and potentially trigger cancer.

It would be fair to say this if they also pointed out the lack of real world evidence to support the concern. Large scale population studies of pure cannabis smokers, as we’ve mentioned several times in the past, have shown no – or at the worst considerably less – link to cancer and such conditions as COPD,  (here here and here for example).

There is an important difference between the document we reviewed last week and this one. ‘A summary of the health harms of drugs’ – last weeks document – is aimed at non-medical professionals (drugs advice workers etc), whereas “Effects of drugs” is aimed at the public and perhaps seems designed to “get the message across” in support of the governments policy, rather than giving objective, factual information?

What makes all this of especial interest though is a development which has happened very quietly and which few of us were really aware, but which will, it is to be hoped, will have far reaching effects. As a part of the new drugs strategy parts of the drugs policy have moved from the Home Office to the dept of Health. I discovered this fact last week when I received a reply to an e-mail I sent to my MP (Simon Wright, Libdem) a few weeks ago asking the government to support Toke Pure. My MP replied on Friday:

The Home Office has advised that the issues you have raised are now the responsibility of the Deartment of Health and our letter has been passed to them for response.

Quite what this means as regards the development of drugs policy regarding cannabis isn’t clear, but it could be very important. We have the strange situation of the department of health warning of dangers from prohibited drugs caused by the unregulated supply side, which of course is a feature of the regime they are implementing. As far as cannabis is concerned they are clearly very aware of the tobacco connection.

We’ll see where this all leads over the next year or so, but it’s not hard to see tensions emerging between the need to introduce health promotion measures and the desire for prohibition.


The “Effects of drugs” page  includes a feedback section for comments. I asked about the difference between the information given here and that published last week, but my comment was never approved.

Footnote to the footnote – the comment (from “NR23Derek”) was eventually published. Thanks to Flake for pointing it out.