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1. INTRODUCTION

BOX 1.4

Definitions of terms related to use of psychoactive substances
Harmful use
A pattern of psychoactive substance use that is causing damage to health. The
damage may be physical or mental.

Hazardous use
A pattern of psychoactive substance use that increases the risk of harmful
consequences for the user.

Intoxication
A condition that follows the administration of a psychoactive substance and results
in disturbances in the level of consciousness, cognition, perception, affect, or
behaviour, or other psychophysiological functions and responses. The
disturbances are related to the acute pharmacological effects of, and learned
responses to, the substance and resolve with time, with complete recovery, except
where tissue damage or other complications have arisen. Complications may
include trauma, inhalation of vomitus, delirium, coma and convulsions, and other
medical complications. The nature of these complications depends on the
pharmacological class of substance and mode of administration.

Substance abuse
Persistent or sporadic drug use inconsistent with or unrelated to acceptable
medical practice. A maladaptive pattern of substance use leading to clinically
significant impairment or distress, as manifested by one (or more) of the following:
failure to fulfil major role obligations at home, school or work; substance use in
situations in which it is physically hazardous; recurrent substance-related legal
problems; continued substance use despite having persistent or recurrent social
or interpersonal problems exacerbated by the effects of the substance.
Source: adapted from Lexicon of alcohol and drug terms, WHO (1994).

qualifying as dependent must be positive on at least one criterion which is
not fully biologically measurable.
Thus a continuing difficulty in the neuroscience of psychoactive
substances is that, while most of their effects shown in Fig. 1.2 are directly
measurable, drug dependence is not, both as it is currently technically defined
and as it is generally understood in the wider society.
However, as will be discussed later in the report, neuroscientists have made
a number of advances in understanding why humans find using these
substances attractive in the first place, what the mechanisms of psychoactivity
are, and the neurobiological changes which occur with repeated heavy use of
a substance.

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