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The War on Drugs: A New Era?

The high profile case of Billy Caldwell, a 12-year-old boy with life-threatening seizures, has again raised questions about the legal status of marijuana.  Billy has a form of epilepsy that causes uncontrollable and constant seizures which do not respond well to treatment.  Using cannabis oil, containing the banned THC component, he was seizure free for more than 300 days.  The case of Billy and others in a similar position has led to a renewed debate in the UK amongst MPs and the media about the medical use of cannabis.  There are now calls for the Home Office to consider the medical use of marijuana. Surely, it is time to consider the evidence?

The medical benefits of marijuana are often overstated, with some even claiming that cannabis can help the body fight cancer.   The actual evidence about the medical uses of cannabis indicates that it has relatively limited benefits.  These include pain management, preventing spasms and seizures, reducing chemotherapy side effects, and stimulating the appetite.  While these benefits are limited, they are crucially important for some people who do not respond well to other treatments.

The discussions about medical marijuana often lead to demands for a wider easing of drug laws.   Most recently Lord Hague, claimed that the ‘war on drugs’ was lost, and called for a lawful, regulated market.  This is the first time that a former leader of the Conservative party has called for radical change.  Responses were predictable, with a spokesperson for Britain’s PM, Theresa May, saying:

“The harmful effects of cannabis are well known, and there are no plans to legalise it. In terms of decriminalising cannabis, there are no plans in that respect. The evidence is very clear – cannabis can cause serious harm when it is misused.”

As David Allen Green has pointed out, if a thing is clear, it needs no ‘very’.  If someone feels the need to insert the adjective ‘very’ it normally indicates that something is ‘not clear’ at all.  So, what is the evidence about the potential harms that cannabis can cause?

Studying the harms that drugs cause is difficult even for drugs legally available and prescribed by doctors.  These difficulties are compounded when the social context of drug use is illegality.  People who use illegal drugs are secretive and wary of revealing their use, even when experiencing harmful side effects.

One approach to assess the relative harm of drugs is thus to pool the knowledge of professionals who work on drug harm and addiction.  This was the approach taken by David Nutt who arranged a panel of 15 experts to consider the relative harms of the most popular drugs in the UK.

The graph below shows how this group of experts ranked the relative harms associated different recreational drugs and, in their estimation, cannabis was less harmful than the two legally available drugs (alcohol and tobacco) included in their study.

These findings were controversial, and there were some valid criticisms of the approach.  For instance, ranking drugs by focusing solely on the physical effects obscures the behavioural complexities of drug use.  Thus, people who smoke tobacco also often drink alcohol. People who smoke and drink are more likely to start fires, which may harm others accidentally. In other words, the ranking assumes an ‘ideal’ drug user who takes one drug at a time and has no other vulnerabilities.  Also using a single index of harm is overly simplistic because it takes no account of the policy environment of illegality.   Is an addict injecting heroin of unknown purity, paid for by crime, bought on the street from a criminal drug dealer and using dirty needles posing the same hazard to themselves and society as an addict using clinically pure heroin, injected with sterile equipment, prescribed by a doctor and provided at no cost by a pharmacist?

Such criticisms are not grounds to dismiss this research entirely.  The Nutt study aimed to produce evidence to generate debate amongst the public and policymakers.  As such it could be seen as being successful, but it did not provide any evidence of the absolute risks of cannabis for the user.

The harms that cannabis can do to a potential user come in two broad varieties; physical or mental.  The physical harms associated with cannabis are almost all caused by the way the drug is consumed via smoking.  The health risks of smoking are very well established.  Marijuana smoke, like tobacco smoke, is an irritant to the throat and lungs and it contains volatile chemicals and tars that raise the risk of cancer and other lung diseases.

In terms of mental harm, one of the frequent claims is that strong herbal marijuana (skunk) causes psychosis. Here evidence about the mental health harms are harder to establish.  Several studies have found an association between cannabis use and psychosis.  In many of these, it is difficult to separate use of cannabis from other behaviours that also lead to poor mental health. Also very few attempt to look at the different types and amounts of cannabis consumed.  One study that sought to address these flaws was that conducted by Martha Di Forti and her colleagues in an area of South London.

This research used a case-control study where groups of individuals (cannabis users) are compared to controls which are similar but do not use cannabis. The results of the study indicated that there was a correlation between the use of strong herbal marijuana (skunk) and psychosis.  A further association was found between daily use of skunk and psychosis. This was an important study that indicates that further research is needed to find out if a popular drug is causing psychosis for some people.

But, there are important qualifications that need to be raised.  Firstly, in a case-control study, it is important to match the cases with the controls as closely as possible. If the control was poorly selected, then this could introduce bias. The authors of the study noted some important differences (gender, ethnicity, and smoking) between cases and controls. They attempted to adjust statistically for these differences.  Yet, they could not be sure that all differences were accounted for and measured. Secondly, the study relied on respondents reporting their past behaviour (i.e. how often and what type of cannabis they consumed).  As such the researchers were relying on the self-reporting of behaviours that have happened some time ago. For example, do users of cannabis, especially if using communally, always know what type of drug they are taking and how strong it was? To be sure of these issues would require the collecting and analysis of drug samples. The practical difficulties of doing so make this nearly impossible, in no small part due to the illegality of cannabis.

Thirdly, and it is an issue that the authors themselves raise, is whether the association between cannabis use and psychotic symptoms is a causal one at all.   It could be that that the association may not be a biological effect but a predisposing factor ‘that could also lead people to select the most potent drug available to use’.  Their analysis, as well as suggesting a causal relationship, could equally imply that a subgroup of the sample was already strongly at risk of psychosis. These people then chose to use high-strength cannabis when it became available. Their use of cannabis was a symptom of psychosis rather than a cause.

The study by Martha Di Forti and her colleagues does indicate that for a subset of users, cannabis use may be risky. But, importantly, the same could be said for many drugs that are both legally bought, legally prescribed and illegally obtained. The actual problem with many studies of drug risk is their narrow focus on harm to the individual.  Such approaches ignore the wider social harms caused by the policy environment of illegality.  Studies have shown that the illegal nature of drug markets, not only increases profits for criminal organisations but that efforts to disrupt drug supply paradoxically leads to more societal violence.  If politicians wanted to act rationally, there would be an urgent need to find alternative regulatory models for drug control.  Sadly in the current climate, there appears to be little political will for such a potentially “radical” approach, and families who can be helped by decriminalisation for medical use face ongoing uncertainty.