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Health should take a pot shot: making a case for medical marijuana

Marijuana provides effective relief in some cases where other therapies have failed. AAP

Lawmakers in the United States introduced legislation overnight to legalise marijuana while giving states the right to regulate, tax and control it. Meanwhile, Australia doesn’t even allow the use of medical marijuana, despite its likely benefits.

Medical use of marijuana is permitted in 15 American states and national surveys show over 70% of the Australian population support the legal availability of medical marijuana.

Medically prescribed marijuana can alleviate cancer pain, the side effects of cancer therapy including nausea and vomiting, and help stop weight loss and other symptoms associated with HIV.

It can be used as therapy for neurologic symptoms associated with Parkinson’s and Huntington’s disease, as well as treating muscle spasms among those with multiple sclerosis, and it can alleviate chronic pain, headaches and anxiety.

And the list goes on.

But in almost every one of these instances, we confront enthusiastic advocates on the one hand and an almost complete absence of convincing evidence of effectiveness on the other.


The United States Institute of Medicine review of the medical uses of marijuana in 1999 gave cautious support for trials of marijuana for treating pain, stimulating appetites and possibly reducing nausea and vomiting.

But there have only been a handful of clinical trials of medical marijuana for a limited number of applications since. Despite this lack of clinical evidence, however, the medical use of marijuana has expanded rapidly in a number of countries.

It seems testimonials of users are proving sufficient to convince legislators to accept the medical benefits of marijuana use. But judgments about efficacy must also include an assessment of how marijuana is consumed.

Where medical marijuana is allowed in the US, it’s prescribed by a medical practitioner and the script “dispensed” by a designated cannabis shop or cooperative store. Cannabis can also be grown at home.

It can be bought as leaves of varying quality or as food, such as hash brownies or cookies. Cannabis leaves have varying concentrations of active ingredients and the product may be partially contaminated by pesticides and fertilizer.

By contrast, medical trials of marijuana generally involve the consumption of a pill, a liquid or it may be administered by injection.

This form is not only different but likely to be more concentrated and administered over a shorter period of time. Even if clinical trials of marijuana were to find that pills or injections were effective, smoking cannabis won’t necessarily produce the same results.

But given the vast majority of people who claim health benefits from marijuana are smokers, the more significant question is whether smoking cannabis reduces pain, improves appetite, reduces neurological symptoms and/or controls nausea or vomiting.

It’s also important to note that whether the benefits of medical marijuana are perceived rather than real is practically a moot point.

In some cases, marijuana is claimed to be effective when nothing else works, that is, when other therapies have often been tried and found to be ineffective.

There’s also a strong argument for patients being allowed to smoke marijuana if it’s the only relief for those using it.

Blocks in the road to medical pot

Legislators tend to be more concerned with the negative consequences of using marijuana. These will depend not only on the quantity, frequency and duration of use, but also on its purity and, most importantly, the reasons for use.

Judgements about the level of harm deemed to be acceptable also require consideration of the underlying condition for which marijuana is being used.

Using marijuana to reduce pain and distress associated with end-stage cancer evokes a quite different calculation of acceptable level of harm, for instance compared with its use to treat a transient headache.

What’s more, if marijuana replaced opioid analgesic medication in the treatment of pain then a judgment of its safety must take compare the level of harm associated with these drugs to that associated with cannabis use.

In any event, assessments of harm will differ depending upon whether the marijuana is medically prescribed, pharmacy dispensed and doctor monitored (as is the case in Canada) or if medical prescribing simply provides access to self medication without the monitoring of the quality and quantity consumed (as is the case in California).

The down side

There are also other factors to take into consideration. Long-term and frequent use of marijuana appears to produce serious mental health problems; it possibly precipitates schizophrenic episodes and psychotic thoughts.

There is also good evidence that smoking marijuana may be demotivating, with users performing poorly at school and university. Other negative consequences include impairment of memory, reduced reaction time and possible impacts on lung function.

Little is known about the likely impact of marijuana use on fetal development and birth outcomes. Many of the constituent chemicals cross the placental barrier, possibly impacting on fetal growth and development.

One could also add to this a concern about the extent to which marijuana might reduce the motivation of the mother or father to fully attend to the care of their child.

While these concerns are valid, there’s no relevant body of evidence to draw upon – whether these negative outcomes occur at all and with what frequency is simply not known.

Humanitarian concerns

Naturally, concerns about the efficacy and safety of medical prescribing of marijuana should be addressed within the appropriate legislative framework.

Legislation in Canada permits prescribing marijuana for a limited number of conditions and involves monitoring or prescribing practices (this is already the case for prescribing of opioids in Australia). This is a low-risk option.

A more controversial approach would be to extend legislation, already in place in some Australian states and territories, to permit individuals to cultivate a small number of plants for their personal use.

Legislation of this kind could permit those with a defined medically-diagnosed condition to grow a small number of plants for their personal use.

There is no reason why marijuana should not be treated in the same way as products such as alcohol and tobacco: their use is mildly discouraged (and certain harmful patterns of use are actively discouraged or punished) but, generally, use is permitted.

The case for introducing legislation to permit the medical prescribing of marijuana, particularly for those who have a serious chronic illness, is relatively strong.

The alternatives – letting people suffer the serious side effects of heavy-duty painkillers or incarcerating patients in chronic pain – are not likely to appeal to legislators.

Few governments want to prosecute and incarcerate the chronically ill or expect to benefit politically from such prosecutions.

With the growing number of people becoming chronically ill, the pressure to permit marijuana use for medical purposes is going to soon become difficult to resist.

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