Home > Encyclopedia of Drugs, Alcohol, and Addictive Behavior > International classification Of Diseases (Icd)

This is the official classification system of the World Health Organization (WHO). As a general system for the classification of diseases, injuries, causes of death, and related health problems, the ICD is used throughout the world as a common frame of reference for statistical reporting, clinical practice, and education. The ICD is a system of categories to which specific disease entities can be assigned consistently in different parts of the world. Recognizing the growing importance of alcohol and drug misuse, the ninth revision of ICD was published in 1975 (ICD-9), and it introduced the terms dependence and abuse into the international nomenclature. Drug dependence was defined as "a state, psychic and sometimes also physical, resulting from taking a drug, and characterized by behavioural and other responses that always include a compulsion to take the drug on a continuous or periodic basis in order to experience its psychic effects, and sometimes to avoid the discomfort of its absence" (WHO, 1977, 198). Alcohol dependence was defined in a similar way. The category Non-Dependent Abuse of Drugs was designed for cases where a person "has come under medical care because of the maladaptive effect of a drug on which he is not dependent and that he has taken on his own initiative to the detriment of his health or social functioning" (WHO, 1978, 43-44).

In 1993, the tenth revision, ICD-10, was introduced—replacing ICD-9 as the official classification system for international use (WHO, 1992a). Chapter 5, which describes mental and behavioral conditions (WHO, 1992b), includes a section for the classification of disorders based on ten kinds of PSYCHOACTIVE substances: ALCOHOL, SEDATIVE-HYPNOTICS, CANNABIS (MARIJUANA), COCAINE, other STIMULANTS, OPIOIDS, HALLUCINOGENS, TOBACCO, VOLATILE SOLVENTS, and multiple drugs. The major disorders associated with these substances are acute intoxication, harmful use, dependence syndrome, withdrawal state, amnesic syndrome, and psychotic disorders (WHO, 1992b). The identification of the substance used may be made on the basis of an interview with the patient, laboratory analysis of blood or urine specimens, or other evidence (such as clinical signs and symptoms or reports from third parties).

Acute intoxication is a transient condition following the ingestion of alcohol or other psychoactive substances. It results in disturbances in consciousness, cognition, perception, mood, or behavior. According to ICD-10, psychoactive substances are capable of producing different types of effect at different dose levels. For example, alcohol may have stimulant effects at low doses, lead to agitation and aggression with increasing dose levels, and produce clear sedation at very high levels. The term pathological intoxication in ICD-10 refers to the sudden onset of violent behavior that is not typical of the individual when sober. This occurs very soon after amounts of alcohol are drunk that would not produce intoxication in most people.

A central feature of the ICD-10 approach to substance-use disorders is the concept of a dependence syndrome, which is distinguished from disabilities caused by harmful substance use (Edwards, Arif, & Hodgson, 1981). The dependence syndrome is defined as "a cluster of physiological, behavioural, and cognitive phenomena in which the use of a substance or a class of substances takes on a much higher priority for a given individual than other behaviours that once had greater value" (WHO, 1992b, 75). A central characteristic of the dependence syndrome is the strong and persistent desire to take psychoactive drugs, alcohol, or tobacco. Another feature is the rapid reappearance of the syndrome soon after alcohol or drug use is resumed after a period of abstinence. A definite diagnosis of dependence is made only if three or more of the following have been experienced during the previous year: (1) a strong desire or sense of compulsion to take the substance; (2) difficulties in controlling substance-taking behavior in terms of its onset, termination, or levels of use; (3) a physiological withdrawal state; (4) evidence of tolerance; (5) progressive neglect of alternative pleasures or interests because of substance use; and (6) persisting with substance use despite clear evidence of overtly harmful consequences.

Harmful use, a new term introduced in ICD-10, is a pattern of using one or more psychoactive substances that causes damage to health. The damage may be: (1) physical (physiological), such as fatty liver, injuries associated with alcohol intoxication, or hepatitis from needle-injected drugs; or (2) mental (psychological), such as depression related to heavy drinking or drug use. Adverse social consequences often accompany substance use, but they are not in themselves sufficient to result in a diagnosis of harmful use.

Chapter 5 of ICD-10 is available in several different versions. The Clinical Descriptions and Diagnostic Guidelines is intended for general clinical, educational, and service use. Diagnostic Criteria for Research is designed for use in scientific investigations and epidemiological studies. A shorter and simpler version of the classification is available for use by primary health-care workers.