Select Committee on Science and Technology Written Evidence


Supplementary memorandum from the Advisory Council on the Misuse of Drugs (ACMD)


  1.  The Council's advice on whether a substance should be brought under the scope of the Act (ie "controlled"), and into which class it should be placed, is based on three domains of harmfulness. These are similar to those used by the Police Foundations Independent Inquiry into the Misuse of Drugs Act.

  2.  These domains comprise:

    —  harms to individuals' physical and mental health;

    —  dependence-producing potential; and

    —  societal harms.

  3.  Harmfulness to physical and mental health encompasses:

    —  acute (ie immediate or short-term) toxicity including the consequences of overdose;

    —  chronic (ie long-term) toxicity particularly after repeated use; and

    —  parenteral use.

  3.1  The impact of a substance on physiological functions, such as the control of respiration or blood pressure, are major determinants of the acute toxicity of a substance.

  3.2  Chronic toxicity generally relates to the adverse effects of a substance following repeated exposure. Adverse effects can, in some instances, occur at long intervals of time after exposure.

  3.3  Parenteral use poses two problems. First, routes leading to very rapid absorption (especially intravenous and inhalational administration) can have serious, and sometimes lethal, consequences. Examples include respiratory arrest following the administration of diamorphine and acute psychotic reactions to inhaled methylamphetamine hydrochloride. Second, the injection of substances carries the potential to transmit blood-borne infections such as human immunodeficiency and hepatitic viruses.

  4.  The likelihood of dependence and addiction relates to:

    —  the intensity of the pleasure derived from use of a substance;

    —  the nature and intensity of psycholgical withdrawal symptoms; and

    —  the nature and intensity of physical withdrawal symptoms.

  4.1  The pleasure that is derived from the misuse of a substance has two components. The initial effect, of rapid onset, is often called "the rush". The euphoria that follows, and which can extend over several hours, is known as "the high". The intensity of "the rush" is, in part, related to the rate of entry of the substance into the circulation and is particularly associated with the intravenous or inhaled routes of administration (see paragraph 3.3 above).

  4.2  Psychological dependence describes a regular user's craving for a particular substance if denied access. It may, or may not, be associated physical dependence.

  4.3  Physical dependence describes non-psychological symptoms and signs that may occur in regular users denied access to a substance. Examples include tremors, sweating, insomnia and increased heart rate.

  5.  The societal harmfulness is assessed from:

    —  the consequences to the individual, and to others, of acute intoxication;

    —  the risks of causing other social harm; and

    —  the costs to the healthcare system arising from the need of individuals, and others, to seek help.

  5.1  Substance misuse may lead to inappropriate behaviour by intoxicated individuals. This includes harms resulting from an inability to concentrate (eg driving) as well as outbusts of aggression. Drugs have also been used to coerce others to engage in sexual activity ("date rape").

  5.2  Substance misuse may have detrimental effects on families including the neglect of children. Substance misuse also leads to acquisitive crime.

  5.3  Substance misuse also has significant impact on the National Health Service as a consequence of the services that have to be provided for dug users themselves, or those they injure.

  6.  These three domains of harmfulness provide a framework by which the Council can evaluated the risks associated with particular substances. Professor David Nutt and his colleagues have developed an assessment matrix which includes all nine parameters of risk (Table 1).

Table 1

Physical harmAcute
DependenceIntensity of pleasure
Psychological dependence
Physical dependence
Social harmsIntoxication
Other social harms
Healthcare costs

  6.1  Using this matrix, and assigning a score to each parameter (0 = no risk; 1 = some risk; 2 = moderate risk; 3 = extreme risk), Professor Nutt and his colleagues have developed an overall harm rating. They have not, as yet, attempted to weight individual parameters.

February 2006

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