Sex, Drugs and Chocolate: The Science of Pleasure. Paul Martin

symptoms or even full-blown psychosis.¹⁴ Some individuals appear to be much more vulnerable to these effects than others. Scientists remain uncertain as to why some people are particularly susceptible in this way, although the explanation is likely to involve some form of interaction between genetic and environmental factors.

      Overall, the emerging evidence suggests that cannabis may be a contributory factor in about 10 per cent of psychosis cases. One analysis published in 2007 concluded that frequent use could double the risk of developing schizophrenia and other psychotic illnesses. That said, psychotic illnesses remain relatively uncommon, in comparison with many other diseases, and most people who use cannabis do not develop them. Cannabis may also heighten the risk of depression and anxiety disorders in vulnerable individuals. One study found that non-depressed people who used cannabis were four times more likely than non-users to become depressed in later years. The use of cannabis preceded the onset of depression, implying that the correlation was not simply the result of already-depressed people turning to cannabis for relief. Even allowing for this and other evidence, there is little doubt that cannabis is still substantially less harmful than, say, cocaine or alcohol. Nonetheless, it is harmful, and probably more so than many of its users once believed.

      All recreational drugs are harmful and some are clearly much more harmful than others. So how should we go about judging the many different drugs in terms of the harm they cause? It all depends, of course, on how you define harm. Should harm be assessed only according to what the drug does to the individual who uses it, or should we also take account of its wider effects on the user’s family, community and society at large? What about drug-related crime, which has as much to do with legislation and social policy as it does with the pharmacological effects of drugs? Collecting high-quality data is another problem. Folklore, prejudice and untested assumptions are readily available when it comes to debating drugs, whereas verifiable scientific evidence is often in short supply. To make matters worse, scientific and medical journals have a slight bias towards publishing studies that find positive evidence of harm rather than those that have drawn a blank. The shortage of solid evidence means that much of the expensive effort to combat drug misuse, whether through law enforcement, treatment or education, may not always be targeted optimally at the drugs that cause the most harm.

      Fortunately, progress is being made on this front and we do now have ways of making more rational judgements about the relative harmfulness of drugs. A significant advance came in 2006, when the UK Parliament’s House of Commons Select Committee on Science and Technology published an authoritative analysis of how different recreational drugs compare in terms of the harm they cause. The report presented a systematic, evidence-based assessment of twenty commonly used drugs, comparing the physical and social harm they cause and their potential to cause addiction. The work was led by Professor David Nutt of Bristol University and Professor Colin Blakemore of the UK Medical Research Council and its findings were published in 2007 in the leading medical journal The Lancet.

      The assessments were made by two panels of independent experts from a range of disciplines, including psychiatrists, chemists, pharmacologists, lawyers and police officers. They drew on the best available scientific and medical evidence. Their analysis took account of three main dimensions, or aspects, of harm: namely, the physical harm caused to the individual user; the broader harm caused to society, including the user’s family and community; and the tendency of the drug to create dependence. Each of these three main dimensions was in turn broken down into a number of sub-dimensions. For example, physical harm was assessed in terms of the drug’s acute effects, its chronic effects and its scope for intravenous use. Some drugs cause mainly acute harm: for instance, cocaine can cause heart attacks and heroin can suppress breathing. Other drugs, notably nicotine, cause most of their harm chronically, through long-term use. Drugs that are taken intravenously tend to be more harmful for several reasons: they produce a bigger ‘rush’, making them more addictive; the user is more likely to overdose; and shared needles spread life-threatening disease such as hepatitis and HIV.

      Each of the twenty drugs was assessed on these various dimensions by the experts, who then debated and revised their judgements according to what is known as an expert delphic procedure. The two groups independently arrived at similar scores, adding to confidence about their validity.¹⁵ The average of all the scores was then used as an overall index of harm for each drug. The resulting rank ordering, in descending order of overall harmfulness, was as follows:

       1 Heroin

       2 Cocaine

       3 Barbiturates

       4 Street methadone

       5 Alcohol

       6 Ketamine

       7 Benzodiazepines

       8 Amphetamine

       9 Tobacco

      10 Buprenorphine

      11 Cannabis

      12 Solvents

      13 4-MTA

      14 LSD

      15 Methylphenidate (Ritalin)

      16 Anabolic steroids

      17 GHB

      18 Ecstasy

      19 Alkyl nitrites

      20 Khat

      One striking feature of this list is how poorly it correlates with the current legal classification of the same drugs. In fact, statistically speaking, there was no significant correlation at all between the rank ordering according to harmfulness and the classification according to current UK legislation (the Misuse of Drugs Act 1971).

      In the UK, illegal drugs are divided into three classes (A, B and C) according to the severity of the penalties incurred for possession or dealing. The highest category, Class A, includes heroin and cocaine, which were also judged by the experts to be the most harmful drugs. However, Class A also includes LSD and ecstasy, which were judged to be among the least harmful. In the UK, you can be sent to prison for up to seven years for possessing a Class A drug and imprisoned for life if convicted of supplying it.

      Alcohol and tobacco, which are legal and unclassified, were assessed to be more harmful than several illegal drugs including cannabis, LSD and ecstasy. If recreational drugs were reclassified according to this evidence-based index of harm, then alcohol would be a Class A drug and tobacco would be Class B. I should stress that I am not trying to imply that making alcohol and tobacco illegal would be either desirable or feasible. The point is simply that the current legal framework has little solid basis in scientific evidence or rational analysis. When measured in terms of the harm they cause, there is currently no clear distinction between legal and illegal drugs.

      For its part, the UK parliamentary committee concluded that there are serious inconsistencies in the legal system for classifying drugs and in the processes by which governments tackle drug use. The committee found no convincing evidence to support the belief that legal penalties deter people from using recreational drugs. It called for a more objective and evidence-based approach which takes better account of the actual harm caused by drugs and places less emphasis on ‘knee-jerk responses to media storms’.

      Similar conclusions were reached by the RSA Commission on Illegal Drugs, following their own two-year study. Their report, which was published in 2007, concluded that ‘the harmless use of illegal drugs is possible, indeed common’. The Commission found that UK drugs laws were driven more by ‘moral panic’ than rational debate. It proposed scrapping the current classification scheme and replacing it with a framework based on harm. The underlying aim should be to regulate the use of drugs in order to prevent harm, rather than trying to prohibit them altogether. The Commission’s chair, Professor Anthony King, called for ‘less foaming at the mouth and more thinking’. I’ll drink to that.

       FIVE And Chocolate

      I adore simple pleasures.