When truth and balance go to pot

Now, more than ever, rational, balanced and informed debate on cannabis use is needed, so that legislation and cultural attitudes can be shaped by right understanding instead of panic and misinformation. Drug Foundation Director Ross Bell weighs some news stories in the balance and finds that coverage is often found wanting.

Reefer Madness was a 1936 propaganda film describing what happened when pushers lured high school students into trying "marihuana". The tragic consequences included a hit and run accident, suicide, rape, weird orgies and a general descent into degradation, debauchery and despair.

The film was originally financed by a church group and had a clear message: Cannabis, the "smoke of hell" and "the devil's harvest", will inevitably lead to drug-crazed abandon, insanity and death.

Cannabis use has become much more widespread in the last 72 years. More than 50 percent of us have tried it at some stage, and those of us who haven't probably know plenty who have. Few today, even amongst pot's most vehement detractors, would argue for the full accuracy of the film's conclusions.

However, a more subtle form of reefer madness persists in the way the effects of cannabis use can be presented by the media. Alarming sounding statistics are often relayed with little attention given to context or negative research findings, and stories are run under shocking or sensationalist headlines.

An example of this is what happened with the Lancet meta-study on cannabis and psychosis published last July. The main report headline, that smoking cannabis increases the risk of schizophrenia by 40 percent, was very widely reproduced in covering media stories. However, the Lancet paper actually stated that the risk pertains to a small proportion of heavy users, and noted that it was related to quantity - the more you use, the greater the risk. It also suggested that 800 cases of schizophrenia would not have occurred if none of the UK's 6.2 million cannabis users had ever tried it.

These figures boil down to an estimated 0.00129% risk of schizophrenia for cannabis users, probably statistically similar to your chances of being hit by an Aston Martin while crossing the road in Cannons Creek.

The Lancet study's authors also admitted that, while a correlation between cannabis and schizophrenia was shown by their research, no causative link could be established.

The point here is not that the possible mental health risks associated with cannabis use should be trivialised - there is a possible link and it shouldn't be ignored - but rather that the prevailing message of the media coverage amounted to wild and inaccurate overstatement.

The next example followed closely on the heels of the Lancet story. A paper by New Zealand researchers appeared in the 31 July edition of the journal Thorax considering the relative impacts of cannabis and tobacco on a range of lung functions. The typical headline above stories reporting on the paper was "One cannabis joint as bad as five cigarettes" and, once again, the full extent of the research went largely unreported.

In actual fact (and in layperson's terms), the research found that:

• tobacco smoking reduced forced expiratory volume (FEV1) but cannabis smoking had no effect
• tobacco smoking reduced maximum mid-expiratory flow (MMEF) but cannabis had no statistically significant effect
• tobacco smoking had no effect on total lung capacity but cannabis increased it with marginal statistical significance
• tobacco smoking reduced carbon monoxide transfer, but cannabis had no effect.

The only test in which cannabis caused worse results than tobacco was in specific airways conductance (sGaw). The negative effect was of marginal significance for tobacco, while smoking cannabis reduced sGaw to the equivalent of smoking between 2.5 and five cigarettes (note the headlines only mention the maximum number).

A ‘novel finding' in the research was that those who used cannabis regularly had an "increased percentage of low density lung tissue" - something that also went largely unreported.

So, in every test but one, tobacco had negative effects while the effects of cannabis were statistically insignificant. But when it comes to the battle to capture readers, that single finding is sufficient to ignore the other findings and claim cannabis to be five times more damaging than tobacco.

At the start of May last year, Associated Press ran a story starting with the following paragraph.

"New findings on marijuana's damaging effect on the brain show the drug triggers temporary psychotic symptoms in some people, including hallucinations and paranoid delusions, doctors say."

The fact that cannabis sometimes produces paranoia and hallucinations is not new news, and I don't want to argue that these are good things. But calling them "damaging effect[s] on the brain" is potentially misleading. ‘Damage' implies permanent, harmful changes whereas the scans in question only reveal what was happening to the brains of the subjects when they were high, not what happened afterwards, or what their brains were doing a day later when they weren't high.

Our brains change temporarily all the time - when we eat chocolate, have sex or go for a run, for example. A temporary change in the brain is not the same as brain damage, and only a study that scanned the same people repeatedly over a long period of time could justifiably claim "physical evidence of the drug's damaging influence on the human brain".

Cannabis use may or may not lead to brain damage in some, but all this study proved was that it alters the brain while a user is under its influence. Admittedly, there's not much of a story in that, but journalists should wait for research that shows permanent damage before claiming it occurs.

Watching the media cover cannabis issues is both fascinating and frustrating. It's fascinating to see how quickly stories that fail to properly place science in context can be churned out and presented to an often uncritical public. It's frustrating in that now, more than ever, rational balanced and informed debate on cannabis use is needed, so that legislation and cultural attitudes can be shaped by right understanding instead of panic and misinformation.

Journalists, as influential shapers of public opinion, have a duty to show some restraint and a willingness to do deeper research so that they don't add further fuel to an already confused and emotional debate.

Let's return to the schizophrenia story as an example. How hard would it be to investigate a corollary or two such as whether schizophrenia rates have increased in line with cannabis use? After all, when tobacco smoking increased across the population, there was a corresponding rise in lung cancer prevalence.

Since the 1940s, percentages of people who have used cannabis have increased from single figures to around 50 percent in many places. Not all use it regularly, or even at all anymore, but if cannabis is more widely used, then any ailment it causes should also have increased. Five minutes on Google shows that this is not the case. In fact, some experts think schizophrenia rates may actually have fallen.

Furthermore, few journalists take the time to put their coverage of risk in context. A 40 percent increase in risk of schizophrenia would sound pretty scary to most, but to epidemiologists, it is not especially noteworthy. They usually don't find risk factors significant until the number hits at least 200 percent, and some major journals won't publish studies unless the risk is at least 300 percent.

Citing other research to help readers get a better understanding of risk magnitude could also be helpful and would be easy to do. A recent study by Johns Hopkins University, for example, found that alcohol can increase the risk of psychosis by 800 percent for men and 300 percent for women. Such a parallel would really help put the dangers of cannabis use into perspective.

The last option open to journalists with a bias for balance would be to cite research that disagrees with or questions the findings in the story they are covering. Leslie Iversen, author of The Science of Marijuana, for example, told the Times of London:

"Despite a thorough review, the authors admit that there is no conclusive evidence that cannabis use causes psychotic illness. Their prediction that 14 percent of psychotic outcomes in young adults in the UK may be due to cannabis use is not supported by the fact that the incidence of schizophrenia has not shown any significant change in the past 30 years."

Comments like these may not help sell papers to a public that prefers its issues to be clear cut, but the role and duty of the media is balance and truth, especially on issues where what we believe and the laws we make can seriously affect so many.

Ross Bell is the Drug Foundation's Executive Director

This article acknowledges a debt to the following blogs:

• More shoddy reefer madness reporting of cannabis risks Transform Drug Policy Foundation, 31 July 2007
• Breaking news: Marijuana gets you high! Maia Szalavitz, 1 May 2007
• Will one joint really make you schizoid? Maia Szalavitz, 30 July 2007