HUMAN PSYCHOPHARMACOLOGY, VOL. 12, S79±S87 (1997) Addiction, Personality and Motivation H. J. EYSENCK Institute of Psychiatry, University of London It is suggested that addictive behaviour, so called, ®ts into a psychological resource model. In other words, the habits in question are acquired because they serve a useful function for the individual, and the nature of the functions they ful®l is related to the personality pro®le of the `addict'. For some people this resource function develops into a form of addiction, and it is suggested that the reason this occurs is related to excessive dopamine functioning. This in turn is used to suggest the nature of the addictive personality. Excessive dopamine functioning is related to the person- ality dimension of psychoticism, and evidence is cited to the eect that psychoticism is closely related to a large number of addictions. The precise reasons for the addictive eects of dopamine are still being debated, but clearly there is a causal chain linking personality and biological factors together in the production of addictive behaviour. # 1997 by John Wiley & Sons, Ltd. Hum. Psychopharmacol. Clin. Exp. 12: S79±S87, 1997. No. of Figures: 3. No. of Tables: 0. No. of Refs: 61. KEY WORDS Ð psychological resource model; dopamine; addictive personality; psychoticism INTRODUCTION: THE RESOURCE MODEL these run as follows: (1) want; (2) freedom of OF ADDICTION choice; (3) psychological dependence; (4) physical The term `addiction' is widely used to characterize dependence, increased tolerance, escalation of the tendency to indulge in certain types of dosage, withdrawal, craving; (5) moral deterior- behaviour to an unusual and possibly harmful ation; (6) intellectual reduction; (7) mental dissolu- extent, addicts often ®nding it dicult or impos- tion; (8) social collapse. He points out that while sible to terminate such behaviour without outside alcohol and drugs ®t all but one of these (freedom help, or even with it. Such behaviour often involves of choice), smoking does not; nor does it remove drugs (alcohol, amphetamine, cocaine, heroin, freedom of choice. This does not remove the etc.), but not necessarily so; in popular parlance possibility that alcohol and drugs may also have one can be addicted to sex, sport, pornography, a resource component; the glib use of the term travel, or work (workaholics). There are two major `addiction' for habituation serves no useful pur- models of addiction, the medical or chemical pose. It may have some meaning if applied to (physical addiction) and the psychological (resource certain drugs, and to certain people. No general- model). As Gilbert (1995) and Warburton (1990) ization should be oered without speci®c proof have pointed out, the term `addiction' has little covering Voss's eight points. These cover what we scienti®c meaning, being employed in dierent might call `genuine' or `medical chemical' addi- ways by dierent writers, and having no agreed tions; in this paper we are using the term in a much interpretation or underlying theory. It is not even broader, non medical sense. known whether addictions (using the term in its The view taken here is that the term `addiction' widest, common sense meaning) is speci®c to one refers to certain types of behaviour that can be substance or activity, or general, i.e. covering interpreted as constituting a resource for the person several dierent areas. Often the term is used in a concerned; in other words, the behaviour confers pejorative sense to suggest that the behaviour in certain bene®ts on that person, and hence the question is a form of disease, requiring medical behaviour in question is continued even though intervention. Voss (1992) has given a list of the there may be certain unwanted consequences, criteria for distinguishing between habituation (or usually occurring only in a statistical fashion resource use) and true or medical clinical addiction; (risk ratios), and after a considerable period of CCC 0885±6222/97/S20S79±09$17.50 # 1997 by John Wiley & Sons, Ltd. S80 H. J. EYSENCK time. As an example, consider smoking. I have i.e. a type of person who is readily addicted to argued that nicotine has a biphasic action, increas- certain types of behaviour which are reinforcing, ing cortical arousal in smaller doses, and decreas- and will continue to indulge in these behaviours ing tension in larger doses (Eysenck, 1980). These even after the circumstances giving rise to them eects can be reinforcing, the former in extraverts have changed. It is this possibility that is being attempting to raise their abnormally low level of discussed in this paper. cortical arousal, the latter in emotionally unstable In this sense of there existing an `addictive people attempting to lower their tenseness. This personality', we would expect genetic factors to analysis suggests that smoking may be related to play an important role, because genetic factors are personality, in the sense that people high on extra- known to be a major determinant of practically all version or neuroticism are more likely to smoke known personality traits, and because the major than people low on either or both these personality dimensions of personality implicated in addiction traits (Eysenck, 1980). As Gilbert (1995) has in particular are known to have high heritabilities shown, both propositions have found considerable (Eaves et al., 1989). Turner et al. (1995) have support in a number of empirical studies. discussed genetic approaches in behavioural It would seem to follow that if people smoke to medicine in detail, and there seems to be little receive certain bene®ts from smoking (resource doubt about the involvement of genetic factors in theory), they would continue in this behaviour alcoholism (Cardoret et al., 1985; Searles, 1988; because it was reinforcing, and it would be dicult McGue, 1995), and smoking (Eaves and Eysenck, to wean them away from it. The problems encount- 1980; Rowe and Linver, 1995; Heath and Madden, ered by most `quit smoking' programmes bear 1995). Eating disorders and obesity, too, have been testimony to this; initial successes are usually shown to have a genetic basis (Cardon, 1995; followed by large scale returns to smoking by Meyer, 1995; Spelt and Meyer, 1995). There is no many subjects of such trials. It would also seem to direct evidence that identical genes are involved in follow that if we could oer smokers alternative dierent types of addiction, but if they are, then ways of obtaining the type of satisfaction they similar personality factors should appear in con- obtain from smoking, e.g. by teaching high nection with each. neuroticism scorers relaxation methods to reduce What is meant by `personality' here is much tenseness, the eect on smoking would be stronger more than just a characterization of a person in and more lasting. O'Connor and Stravinski (1982) terms of traits of one kind or another. Figure 1 will have demonstrated that this is indeed so, thus make it clear that psychometric traits do indeed ®ll giving strong support to the resource theory. the centre of the picture, but such trait character- ization is only part of a much larger nomological network (Eysenck and Eysenck, 1985). There is PERSONALITY AND ADDICTION much evidence that all aspects of personality are Can we extend such a personality type theory to strongly determined by genetic factors (Eaves et al., the problem of addiction? Obviously some people 1989). DNA cannot, of course, aect behaviour ®nd it easier than others to give up addictive directly, and hence we have biological intermedi- sources of grati®cation. Many US soldiers acquired aries (proximal antecedents) linking DNA and the habit of smoking opium in Vietnam, but had behaviour. Theories of personality can be tested in no diculty giving it up on their return; others the experimental laboratory (proximal conse- became hopeless addicts. One possible dierence quences), and ®nally give rise to predictions may be found in the circumstances encountered by involving social behaviour (distal consequences). the people concerned. Many people took up The alleged `addictive behaviours' would fall into smoking during the war because of the stress this last category, and hence would require not only involved, and had no diculty in giving it up after a link with psychometric personality traits, but also the war, because the stress was removed. A resource with biological antecedents. We have tried to go model can easily explain such examples of quitting some way towards ®lling in the various parts of made easy by changing circumstances. However, such a systemic view. clearly this is not enough, because `addictive' The ®rst step in such a search for causal connec- people remain wedded to their addiction in spite tions must be an inductive one, namely a search for of changing circumstances. This raises the possibi- personality correlates of addiction. There are three lity that there may exist an `addictive personality', major dimensions of personality, P (psychoticism), HUMAN PSYCHOPHARMACOLOGY, VOL. 12, S79±S87 (1997) # 1997 by John Wiley & Sons, Ltd. ADDICTION, PERSONALITY AND MOTIVATION S81 Figure 1. Nature of personality structure Figure 2. The psychoticism continuums, with PA denoting increasing probability of functional psychosis with higher psychoticism scores E (extraversion) and N (neuroticism); these are may be useful in introducing it. The underlying uncorrelated with each other, and cover dierent theory states that there is a dimension of person- areas of personality (Eysenck and Eysenck, 1985). ality which relates to a person's liability to func- As we shall see, it is particularly the psychoticism tional psychosis, as shown in Figure 2 (Eysenck, dimension that has been found to be correlated 1992). Psychoticism measures a dispositional vari- with addictive behaviour, and hence a few words able; P has to be combined with stress to produce # 1997 by John Wiley & Sons, Ltd.