HUMAN , VOL. 12, S79±S87 (1997)

Addiction, and

H. J. EYSENCK Institute of , 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 e€ect that psychoticism is closely related to a large number of addictions. The precise reasons for the addictive e€ects 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 dicult 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), 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 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 o€ered 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 di€erent might call `genuine' or `medical chemical' addi- ways by di€erent 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 di€erent 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 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 e€ects 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 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 dicult 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 o€er smokers alternative di€erent 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 e€ect 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 theory to strongly determined by genetic factors (Eaves et al., the problem of addiction? Obviously some people 1989). DNA cannot, of course, a€ect 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 diculty giving it up on their return; others the experimental laboratory (proximal conse- became hopeless addicts. One possible di€erence 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 diculty 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 di€erent 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. HUMAN PSYCHOPHARMACOLOGY, VOL. 12, S79±S87 (1997) S82 H. J. EYSENCK

Figure 3. Traits characteristic of psychoticism actual psychiatric symptoms. We are dealing this scale, addicts had mean scores almost twice as throughout with non-psychotic individuals in our high as controls (Gossop and Eysenck, 1980). studies, but of course the biological substratum of P The personality patterns of criminals are similar would have to be similar to, or identical with, that to those of drug addicts, particularly in having high of schizophrenia to make the theory acceptable. P and N scores (Eysenck and Gudjonsson, 1989). Gray et al. (1991) have argued that there is indeed Gossop and Eysenck (1983) tested 221 drug addicts such a similarity as we shall discuss presently. and over 1000 criminals on the P, E, N and L scales. The actual traits which intercorrelate together to They found addicts higher on P, lower on E, higher make up the higher-order factor of psychoticism on N (particularly the women), and lower on L. In are shown in Figure 3; the evidence for the exist- other words, the di€erences in personality patterns ence of such a factor, and the evidence for its are similar to those obtained with normal controls. identi®cation as psychoticism, are given elsewhere These studies were done with traditional drug (Eysenck, 1992). Is it true that addictive behaviour takers. Smokers, if we are willing to consider them is largely determined by P, and to a smaller extent `addicted' in the sense of continuing to smoke by N (neuroticism)? Early studies by Gossop cigarettes in spite of many health warnings, have (1978) and Teasdale et al. (1971) showed that been found to have high-P scores, and it may be drug-dependent groups had typically high levels of noted that nicotine is an indirect dopamine agonist psychoticism, together with elevated scores on (Spielberger and Jacobs, 1982; Gilbert, 1995). The neuroticism; they also had somewhat lower levels relevance of this point will be made clear below; of extraversion than controls. just note that dopamine plays an important part in A larger and more detailed study comparing the Gray et al. (1991), as well as in other theories of drug addicts and controls was carried out by schizophrenia. Gossop and Eysenck, (1980) who found that for As far as alcoholism goes, two dimensions both males and females high-P was an important appear to be relevant to its aetiology (Sher, 1991; discriminant, with high neuroticism (N) also McGue, 1995). The ®rst resembles psychoticism, important, but less so for women than for men. with characteristics like impulsivity, inattention They also suggested that the high-N scores might and character disorders. The second is neuroticism, have been in¯ated for various reasons. Low extra- or `negative emotionality', with a tendency to version (E) scores were also again characteristic of experience negative moral states and psychological drug addicts. The test used also contained a Lie distress. Scale (L) which essentially measures conformist Rather more interesting and unusual is work behaviour, and usually correlates negatively with P; with bulimics who have been suggested to share low L scorers were characteristic of the drug many similarities with addicts (Garrow et al., addicts. On the basis of these results, the authors 1975). The outcome was a clear con®rmation of constructed an addiction scale consisting of the the hypothesis, with patients having higher P and 32 most discriminating items (all at p < 0Á001). On N scores, and lower E and L scores, than controls

HUMAN PSYCHOPHARMACOLOGY, VOL. 12, S79±S87 (1997) # 1997 by John Wiley & Sons, Ltd. ADDICTION, PERSONALITY AND MOTIVATION S83

(Feldman and Eysenck, 1986). The study was con®rms a clear relationship between neuroticism repeated by Silva and Eysenck (1987), with similar and the use of drugs and alcohol'. However, `the results, comparing 59 female patients su€ering from relationship between extraversion and the use of anorexia nervosa with 122 bulimics; the bulimics drugs and alcohol is much less clear'. Francis adds score signi®cantly higher than the anorexics on P his own rather novel investigation of personality and N, and lower on L. On the addiction scale they and attitude towards substance use among 13± also scored signi®cantly higher. Another unusual 15-year-old children, using a large sample of sample was made up of gamblers (Blaszczynski 19 349 subjects. A negative attitude to drug usage et al., 1985), who had signi®cantly higher P and N correlated 0Á34 with P, ‡0Á33 with L, 0Á16 with scores than controls. E and 0Á03 with N. Controlling for sex slightly Observed personality characteristics of drug raised the correlation for P, L and E, leaving that addicts are not culturally determined but can be for N unchanged. In so far as attitude is predictive observed in other cultures as well as in Europe. A of use and abuse, these ®gures support ®ndings on Saudi Arabian group of drug addicts was tested by addiction, except for the low values for N. Abu-Arab and Hashem (1995), showing again the Given that P is the major element in addiction, same high P-high N patterns observed in European it may be worthwhile to enquire about the preva- subjects. These authors also refer to another study lence of addiction in two large groups character- by Abu-Arab (1987), showing similar correlations ized by high P scores, namely criminals (Eysenck with alcoholism (see also Hurlburt et al., 1982). and Gudjonsson, 1989) and creative people and In a recent study, Mann et al. (1995) used the (Simonton, 1994). It is hardly necessary to NEO Personality Inventory (Costa and McCrae, discuss in detail the close relationship between 1991), which has two scales (A Ð agreeableness addiction and criminality; this is too well known to and C Ð conscientiousness) which have a high require elaboration. As regards creative artists and negative correlation with P; they also have scales scientists, the evidence has been reviewed by for E and N. They compared a group of addicts Simonton (1994). Note also that excessive dopa- with controls, and found the expected di€erences, mine functioning has also been found in criminals with addicts lower on A and C, and also on E, but (Raine, 1993; Masters and McGuire, 1994). These higher on N. I have been unable to ®nd any studies links are at present merely correlational, and would of addiction that found results in a direction surely deserve closer study, particularly as concerns opposite to that indicated, i.e. high P, high N, causal mechanisms. low L and possibly low E. Sex di€erences do not change this pattern, but women have less elevated N di€erences. Particularly impressive are the BIOLOGICAL ANTECEDENTS universally high P scores of addicts, as demanded OF ADDICTION by our theory. We must now turn to the biological antecedents These are just a few of the early studies using the which characterize addiction; if our theory cannot Eysenck Personality Questionnaire scales. Francis accommodate such ®ndings, then clearly it cannot (1996) has listed all available studies for addiction serve the unifying function hoped for it. In what to alcohol, opium, heroin, benzodiazepines, etc.; in follows I shall rely very much on a theory put all, he found 19 studies speci®cally linking P and forward by Joseph et al. (1996), based as it is on addiction, and 23 linking N and addiction. (The much empirical work. As they point out, drugs larger number of studies using N is due to the fact often associated with abuse and addiction char- that many more investigators used N scales than P acteristically share the feature of being able to scales). Extraversion gave 10 negative and two increase neurotransmission in the mesolimbic dopa- positive correlations with addiction, as well as mine system. This system ascends from the neural 12 studies without signi®cant results. The Lie Scale tegmental area in the midbrain to the limbic areas shows seven studies giving negative correlations associated with , including the nucleus with addiction, two with positive, and three with accumbens (NAc) and the amygdala. Di Chiara and insigni®cant correlations. Imperato (1988) have shown that various addictive Francis summarized his survey of addictive drugs, such as amphetamine, cocaine, nicotine, behaviour by saying that the literature `con®rms morphine and alcohol a€ect extracellular dopamine that psychoticism is a key personality factor in this levels in the NAc of the rat. The data suggest area'. Furthermore, `the majority of studies also innervation from the AIO nucleus in the ventral

# 1997 by John Wiley & Sons, Ltd. HUMAN PSYCHOPHARMACOLOGY, VOL. 12, S79±S87 (1997) S84 H. J. EYSENCK tegmental area, and leave little doubt that all of 1988; Stolerman, 1992). What renders these results these drugs of abuse can activate the mesolimbic interesting is that NAc activity is also increased system at low doses. This is so although these during and ends shortly after food reward, water common e€ects are brought about by diverse reward, and sexual activity in male rats. These are pharmacological action of the drugs in question. all rewarding, in the sense that they reinforce The relationship between addiction and dopa- (increase) the likelihood of behaviour associated mine activity is given further support by a recent with them Ð in other words, animals will work to study (Fowler et al., 1996). They report that brains obtain access to these reinforcers. Stimuli asso- of living smokers show a 40 per cent decrease in the ciated with these reinforcers also acquire secondary level of monoamine oxidase relative to non reinforcing properties through a simple Pavlovian smokers, or former smokers. They draw attention conditioning process. Such secondary rewards are to the fact that MAO is involved in the breakdown also associated with dopamine activity in the NAc of dopamine. `MAO inhibition is therefore associ- (Damsma et al., 1992; Phillips et al., 1993). This ated with enhanced activity of dopamine' (p. 733). combination of ®ndings might suggest a simple The authors remark on the prevalence of smoking resource theory: drugs of abuse produce an in psychiatric disorders, and of course low increase in dopamine in the NAc. Addiction occurs MAO levels are associated with psychopathological because the drugs involved produce stronger behaviour (Zuckerman, 1991). What is important reinforcing e€ects in the brain systems of high-P for our theory is that dopamine functioning has (dopamine active) people than those of low-P been linked experimentally with high P scoring (dopamine inactive) people. (Gray et al., 1994); this is the fundamental link Wise and Rompre (1985) have reviewed the huge between personality and biological reality. literature on brain dopamine and reward. They Von Knorring and Oreland (1985) lend further point out that `the evidence is strong that dopamine support to the involvement of MAO in addiction in plays some fundamental and special role in the a paper which studied the smoking habits of an rewarding e€ects of brain stimulation, psycho- unselected series of 1129 18-year-old men from the motor stimulants, opiates, and food' (p. 270); they general population. `Regular smokers were found go on to say that dopamine is not the only reward to be extraverts, sensation seekers who were easily transmitter, and that dopaminergic neurons are not bored and with a strong tendency to avoid mono- the ®nal common path for all rewards. They tony. They also had a lower than average intellec- conclude that `in all likelihood, the dopamine tual level, and were more prone to the abuse of system plays some very general role in mood and alcohol, glue, cannabis, amphetamine and mor- movement, a role that is essential to reward phine. Furthermore, they had a low platelet MAO function as well as to other aspects of motivated . . . Ex smokers had personality traits, intellectual ' (p. 221). levels and platelet MAO of the same magnitude as There are problems associated with such a non smokers: this may be the reason why they were theory. In the ®rst place many animal studies have able to give up smoking' (p. 327). This study shown that stresses and aversive stimuli of various strongly supports the hypothesis of a generally sorts are also associated with increased dopamine addictive person, and connects this addictive release in the NAc (e.g. Young et al., 1992; personality to low platelet MAO. The personality Saulskaya and Marsden, 1995). Thus not only traits involved pertain to P as much or more than rewarding but also punishing stimuli produce to extraversion; it is regrettable that the P scale was increased dopamine release in the NAc. And, as not used in this study. in the case of rewarding stimuli, secondary aversive These data suggest the existence of a general properties acquired through a process of Pavlovian basis for addiction, in enhanced dopamine func- conditioning also gain the ability to increase tioning, regardless of what substance is involved. dopamine activity in the NAc (Young et al., One possible hypothesis to explain this general- 1992). Thus, as Joseph et al. (1996) point out, ization is based on the fact that the mesolimbic `while all rewarding stimuli so far studied increase dopamine system is involved with the mechanism DA activity in the NAc, it is by no means the case of reward and reinforcement. Studies involved in that all stimuli which increase DA activity in the this type of research relate to experiments on NAc are rewarding' (p. 58). self stimulation, drug self administration, and Another problem with a simple reward theory is conditioned place preference (Fibiger and Phillips, that neutral stimuli presented in a regular temporal

HUMAN PSYCHOPHARMACOLOGY, VOL. 12, S79±S87 (1997) # 1997 by John Wiley & Sons, Ltd. ADDICTION, PERSONALITY AND MOTIVATION S85 association, resulting in the formation of a con- novel) stimuli produce an orienting reaction which ditioned association, as indexed in the sensory pre- increases cortical arousal levels. Increased DA conditioning paradigm, are also associated with release will reduce the probability that stimuli will increased DA activity in the NAc, while the be ignored as familiar and non productive. Again, identical stimuli presented in a non-associated as before, we must note that much further work will manner are not (Young et al., 1995). Thus, as be required (perhaps by looking at indices of Joseph et al. (1996) summarize the evidence, cortical arousal) before this hypothesis is regarded `increased DA activity in the NAc is associated as acceptable. If reduction in latent inhibition does with primary and secondary motivational stimuli, indeed raise cortical arousal, this might account for whether rewarding or aversive, and with associa- the fact that low extraversion is sometimes corre- tions between neutral stimuli which result in lated with addiction; low arousal is the major conditioning. Perhaps the common factor here is psychophysiological precursor of extraversion, and that all of these stimuli, or con®guration of stimuli, heightening arousal is regarded as desirable by are salient to the animal' (p. 58). extraverts. High P scorers, of course, also have low The fact that dopamine has several di€erent arousal levels. e€ects does not necessarily rule out the possibility The di€erent hypotheses mentioned here to that it is its e€ect on the pleasure centres that is account for dopamine action increasing addictive crucial for addictive behaviour. Aversive and behaviour are not antagonistic to each other. It is conditioning e€ects may be irrelevant to addiction; quite possible that all are correct, and operate to a the complexity of neurotransmitter activity is well di€ering degree in di€erent people, depending on known. But in order to maintain this theory we their position on P, E and N. There seems little would require more experimental support than is doubt that personality plays a prominent part in available at the moment. Possibly conditioning relation to addiction, regardless of the type of provides another plausible bridge between addic- addiction, and that dopamine plays a large media- tion and dopamine, in that addictive behaviours ting role between DNA and personality, particu- are conditioned behaviours, with the positive e€ects larly P. These facts suggest the direction in which of the addictive behaviours acting as uncondi- future research may go with advantage; there are tioned response variables reinforcing these beha- plenty of promising hypotheses to keep such viours more strongly in people more likely to form research going. strong conditioned responses. Joseph et al. (1996) put forward a rather di€erent theory, linked with latent inhibition (LI) (Lubow, REFERENCES 1989). LI refers to an experimental two-stage Abu-Arab, M. (1987). Some correlates of personality in arrangement in which a neutral is pre- a group of alcoholics. Protialkoholicky Obzor, 22, 36. sented a number of times without any contingent Abu-Arab, M. and Hashem, E. (1995). Some personality reinforcement, e.g. a sound is presented randomly correlates in a group of drug addicts. Personality and while the subject is carrying out an (irrelevant) Individual Di€erences, 19, 649±653. learning task. 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