Types of drug dependence
The definition of drug dependence used in this article includes a broad base and includes dependence on a very wide range of drugs, some of which are used medically (e.g. opiates, sedative hypnotics), while others (khat, hallucinogens, cannabis) are not. It is perhaps not surprising that the characteristics of the dependent state vary according to the type of drug. Some drugs cause marked physical dependence with a correspondingly severe withdrawal syndrome; others cause less physical dependence but profound psychological dependence. The extent to which tolerance develops also varies with different classes of drugs. Caffeine,
consumed as it is by most people in tea or coffee, produces a limited degree of psychological dependence sometimes manifested as ‘I can’t get going in the morning without my cup of tea’, and a mild state of physical dependence with headaches on drug withdrawal. This degree of dependence is not particularly harmful either to the individual or to society, although it should be noted that a more severe degree of dependence on caffeine (often in cola-type drinks) may sometimes arise. However, several classes of dependence-producing drugs affect the central nervous system profoundly, producing stimulation or depression and disturbances in perception, mood, thinking, behaviour or motor function. The use of these drugs may produce individual, public health and social problems and is, therefore, a justifiable cause for concern. There is no wholly satisfactory way of classifying drugs of abuse and dependence because drugs with similar pharmacological effects may produce quite different types of dependence. Cannabis, for example, has both sedative and hallucinogenic effects, but the pattern of its abuse, by millions of people worldwide, is quite different to the abuse of barbiturates or benzodiazepines which are sedatives, and LSD which is a hallucinogen. The Tenth Revision of the International Classification of Diseases (ICD-10)4 recognizes the psychoactive drugs or drug classes listed in Table 1.1, the self-administration of which may produce mental and behavioural disorders, including dependence (see Chapter 6). Abuse and dependence on a wide range of other drugs also occurs. For example, abuse of minor analgesics, such as aspirin and compound analgesics, is so widespread that it has been estimated that there may be as many as a quarter of a million analgesic abusers in the UK alone. This problem is frequently ignored in studies of drug abuse and dependence, firstly because it involves drugs over which there are no legal controls (or only very limited ones) and which may be easily obtained from outlets such as newsagents, supermarkets and even slot-machines, as well as from pharmacists. Secondly, it is easy to dismiss it as uninformed self-medication by a group ignorant of the dangers of excessive use of these drugs. In many ways, however, those who abuse minor analgesics (and other drugs not included on the above list) resemble those who abuse illicit or restricted drugs: they often deny their drug-taking
and may go to considerable lengths to conceal it; they often admit that they take the drugs for the feeling of well-being that they induce and, in the case of aspirin, specifically to experience the dangerous state of salicylism (aspirin intoxication) that they find pleasurable. Above all, they are psychologically dependent on these drugs: showing craving, drug-seeking behaviour and an inability to stop taking them7 . In addition to the drugs already discussed, there are many other drugs, each of which is abused by a few people who may then become dependent on them. Some, such as the antiparkinsonian anticholinergic drugs, may be taken for their psychic effects. Others, such as purgatives or anticoagulants may be taken to produce fictitious disease, those who abuse them often concealing this fact, and seeking and apparently enjoying repeated, intensive medical investigation and care. Finally, some drugs prescribed for somatic disease may be taken excessively, primarily to avoid unpleasant withdrawal symptoms, although eventually a true dependent state may develop. For example, increasing doses of ergotamine, prescribed for migraine, may be consumed to avoid withdrawal headaches, and increasing doses of steroids may be taken to avoid unpleasant psychological effects on drug withdrawal. The family, friends and colleagues of doctors, as well as doctors themselves, may be vulnerable to this type of drug abuse if their powers of persuasion overcome normal professional prescribing practices. These, much less-common types of drug dependence have been introduced into the discussion because their existence illustrates and emphasizes a very important point: that abuse and dependence do not only occur with ‘dangerous’ psychoactive drugs. In other words, dependence is not just a manifestation of a specific drug effect, but is a behaviour profoundly influenced by the individual personality and the environment, as well as by the specific drugs that are available. As a behaviour, drug dependence is similar to compulsive gambling and compulsive eating, and what all these have in common is an overwhelming psychic drive to behave in a certain way. A better understanding of this compulsion and of the nature of intrusive thought will enable us to reach out towards a better understanding of drug dependence and a whole range of similar human behaviours.
The definition of drug dependence used in this article includes a broad base and includes dependence on a very wide range of drugs, some of which are used medically (e.g. opiates, sedative hypnotics), while others (khat, hallucinogens, cannabis) are not. It is perhaps not surprising that the characteristics of the dependent state vary according to the type of drug. Some drugs cause marked physical dependence with a correspondingly severe withdrawal syndrome; others cause less physical dependence but profound psychological dependence. The extent to which tolerance develops also varies with different classes of drugs. Caffeine,
consumed as it is by most people in tea or coffee, produces a limited degree of psychological dependence sometimes manifested as ‘I can’t get going in the morning without my cup of tea’, and a mild state of physical dependence with headaches on drug withdrawal. This degree of dependence is not particularly harmful either to the individual or to society, although it should be noted that a more severe degree of dependence on caffeine (often in cola-type drinks) may sometimes arise. However, several classes of dependence-producing drugs affect the central nervous system profoundly, producing stimulation or depression and disturbances in perception, mood, thinking, behaviour or motor function. The use of these drugs may produce individual, public health and social problems and is, therefore, a justifiable cause for concern. There is no wholly satisfactory way of classifying drugs of abuse and dependence because drugs with similar pharmacological effects may produce quite different types of dependence. Cannabis, for example, has both sedative and hallucinogenic effects, but the pattern of its abuse, by millions of people worldwide, is quite different to the abuse of barbiturates or benzodiazepines which are sedatives, and LSD which is a hallucinogen. The Tenth Revision of the International Classification of Diseases (ICD-10)4 recognizes the psychoactive drugs or drug classes listed in Table 1.1, the self-administration of which may produce mental and behavioural disorders, including dependence (see Chapter 6). Abuse and dependence on a wide range of other drugs also occurs. For example, abuse of minor analgesics, such as aspirin and compound analgesics, is so widespread that it has been estimated that there may be as many as a quarter of a million analgesic abusers in the UK alone. This problem is frequently ignored in studies of drug abuse and dependence, firstly because it involves drugs over which there are no legal controls (or only very limited ones) and which may be easily obtained from outlets such as newsagents, supermarkets and even slot-machines, as well as from pharmacists. Secondly, it is easy to dismiss it as uninformed self-medication by a group ignorant of the dangers of excessive use of these drugs. In many ways, however, those who abuse minor analgesics (and other drugs not included on the above list) resemble those who abuse illicit or restricted drugs: they often deny their drug-taking
and may go to considerable lengths to conceal it; they often admit that they take the drugs for the feeling of well-being that they induce and, in the case of aspirin, specifically to experience the dangerous state of salicylism (aspirin intoxication) that they find pleasurable. Above all, they are psychologically dependent on these drugs: showing craving, drug-seeking behaviour and an inability to stop taking them7 . In addition to the drugs already discussed, there are many other drugs, each of which is abused by a few people who may then become dependent on them. Some, such as the antiparkinsonian anticholinergic drugs, may be taken for their psychic effects. Others, such as purgatives or anticoagulants may be taken to produce fictitious disease, those who abuse them often concealing this fact, and seeking and apparently enjoying repeated, intensive medical investigation and care. Finally, some drugs prescribed for somatic disease may be taken excessively, primarily to avoid unpleasant withdrawal symptoms, although eventually a true dependent state may develop. For example, increasing doses of ergotamine, prescribed for migraine, may be consumed to avoid withdrawal headaches, and increasing doses of steroids may be taken to avoid unpleasant psychological effects on drug withdrawal. The family, friends and colleagues of doctors, as well as doctors themselves, may be vulnerable to this type of drug abuse if their powers of persuasion overcome normal professional prescribing practices. These, much less-common types of drug dependence have been introduced into the discussion because their existence illustrates and emphasizes a very important point: that abuse and dependence do not only occur with ‘dangerous’ psychoactive drugs. In other words, dependence is not just a manifestation of a specific drug effect, but is a behaviour profoundly influenced by the individual personality and the environment, as well as by the specific drugs that are available. As a behaviour, drug dependence is similar to compulsive gambling and compulsive eating, and what all these have in common is an overwhelming psychic drive to behave in a certain way. A better understanding of this compulsion and of the nature of intrusive thought will enable us to reach out towards a better understanding of drug dependence and a whole range of similar human behaviours.
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