By William E. McAuliffe, Ph.D. Robert A. Gordon, Ph.D.

The theory summarized here emerged from systematic empirical research and critical reexamination of prior literature concerning opiate addiction (McAuliffe and Gordon 1974, 1975, 1979; McAuliffe 1975a,b, 1979; Gordon 1979).

This effort has resulted in the firm establishment of euphoric effects as one of the several major sources of reinforcement deriving directly from opiates even in chronic addiction (McAuliffe and Gordon 1974, 1975), and clarification of the conditions under which euphoric effects are available even to many first-time users of opiates (McAuliffe 1975a).

Prior to these investigations, most social scientists accorded a relatively restricted role to euphoria (e.g., Lindesmith 1947), and this view also found considerable acceptance among physical and medical scientists. Euphoric effects sometimes reported or assumed in the medical literatures were often considered atypical.

Now, with such fundamental issues behind us, it is possible to use a reinforcement theory to organize and interpret many of the more detailed empirical phenomena of opiate abuse, where that theory has available to it for explanatory purposes the full range of effects produced by opiate drugs. The present digest reflects the current stage of development of such a theory. (For a full statement, see McAuliffe and Gordon 1979.)

A BRIEF OVERVIEW THE CAUSE OF ADDICTION

According to our theory, opiate addiction is caused by the extremely potent reinforcing effects of opiate drugs. These effects consist of euphoria (including the impact effect or “rush”), reduction of withdrawal, and miscellaneous psychotherapeutic and analgesic properties, which combine independently to produce a complex schedule of reinforcement for taking opiates.

Opiate use, consequently, is an operantly conditioned response whose tendency becomes stronger as a function of the quality, number, and size of the reinforcements that follow it. Addiction, in our theory, refers to the strength of the drug-taking response and is thus a continuous variable, rather than a qualitatively different state.

Addiction begins to grow with the first reinforced opiate-taking response. When the opiate-taking response has become powerful enough, as the result of sufficient reinforcement, the user experiences an increased desire or “craving” for opiate effects. Craving may, however, be contingent upon the presence of discriminative stimuli that signal to the user that reinforcement for taking opiates is indeed possible; for example, that he or she is not under opiate blocking by antagonists such as naloxone at the time.

An experiment by Mirin et al. (1976, figure 3) found that addicts’ self-reported intensity of craving rose rapidly when heroin was readily available, fell rapidly under methadone detoxification, and remained low when heroin was again made available while the subjects were on a blocking regimen receiving naltrexone.

A more meaningful definition of “addiction.” In common parlance, persons are said to be “addicted” when they have become physically dependent or at least seem unable to refrain from using a drug. We regard these events as merely signalling that a sufficient history of reinforcement has probably been acquired to impel a high rate of use.

In the case of strong physical dependence, the user is confronted with the necessity of responding at a minimal rate (which happens to be also a high rate) if immediate use for whatever reason is to continue at all and if a negative reinforcer is to be successfully avoided. In our theory, there is no single point at which an individual suddenly becomes “addicted.”

Instead, the individual’s addiction develops insidiously and varies continuously, so that what others seemingly mean when they label someone an “addict” is merely a person with a strong addiction (i.e., a history of reinforced drug taking sufficient to outweigh the more acceptable reinforcers of life, such as are associated with one’s job, family, friends, sex life, and respectability).

Physical dependence on opiates is neither a necessary nor a sufficient condition for the development of addiction. Physical dependence simply sets the stage for experiencing withdrawal distress, reduction of which constitutes one of the drug’s powerful reinforcing effects.

Other effects (principally euphoria, but including secondary social gains, and relief of pain, anxiety, and fatigue) can themselves produce or contribute to addiction. Most, if not all, street addicts are reinforced in the early stages of heroin use by effects other than withdrawal, and their drug-taking response at that stage must be strong enough so that it occurs every day for a few weeks in order for them to develop physical dependence.

Since contemporary opiate abusers know about physical dependence and usually prefer to avoid it, their daily use prior to dependence must reflect the existence of an addiction of some strength. We have interviewed heroin users who had never been dependent but who were either adamant about wanting to continue heroin use despite the risks and severe social pressures or convinced that they could not stop even though they wanted to.

We and other researchers (Lindesmith 1947; Robins 1974a) have also interviewed persons who had used opiates compulsively on a daily basis for many months without ever interrupting long enough to experience withdrawal sickness.

The distinction between addiction and physical dependence is also evident in detoxified addicts who are temporarily free of dependence but who are still strongly addicted, as witnessed by their expressed desire for opiates and their disposition to relapse, and in those medical patients who become physiologically dependent without knowing it but who remain indifferent because they have not developed a strong psychological attachment to opiates. (See Lindesmith 1947 for examples.)

Our theory implies that singling out any particular point in a reinforcement history as the stage of “addiction” is more or less arbitrary. We recognize, however, that there are advantages associated with employing physical dependence as a tacit operational criterion of “addiction.”

Because the withdrawal syndrome (1) is a salient phenomenon that usually implies a substantial history of prior reinforcement, (2) introduces a potent new reinforcer, and (3) sets a new lower bound on the rate of continued use, the point at which physical dependence appears serves as a useful peg on which to hang a definition of “addict” that signals important changes in lifestyle.

This highly visible point divides opiate users into those with and without such major lifestyle changes with great efficiency (i.e., low false-positive and false-negative rates). Indeed some addicts date their being “hooked” from the time they recognized major changes in their lifestyle, such as intense craving, getting fired from their job, or realizing that they preferred heroin to sex (Hendler and Stephens 1977, p. 41).

Convenient though it may be, there are important disadvantages associated with equating addiction with physical dependence as laymen do, or with making physical dependence a necessary but not sufficient condition of addiction in a theory of opiate use (Lindesmith 1947).

By encouraging the notion that physical dependence is necessary in order for addiction to be present, one also encourages the seriously misleading impression--according to our theory--that a user is relatively safe as long as physical dependence is avoided. This conception opens neophytes to the insidious features of onset underscored by the reinforcement perspective, according to which predependence use is more dangerous than seems apparent because the actual onset accrues gradually with each reinforcement.

Clearer recognition of withdrawal sickness as but another potent source of reinforcement should dispel some of the controversy over whether “addiction” is defined as a physical phenomenon or as a psychological phenomenon and thus also clarify the related issue of whether drugs that do not entail physical dependency are “addicting.”

The distinction between the two conditions is certainly a valuable one, since one adds a potent reinforcer that the other lacks, but the decision to regard one or the other state as addiction proper is, from our theoretical standpoint, basically arbitrary, and hence the theoretical discontinuity between the opiate and nonopiate types of chronic drug use no longer obtains.

The role of psychopharmacological factors. While we grant that an individual’s personality, expectations, and the setting in which an opiate is used play important roles in the addiction process, we hold that opiates themselves have intrinsic properties that cause them to be powerful reinforcers and therefore potently addictive.

Experimental research with animals demonstrates that personality variables, peer pressure, poverty, or other social environmental factors are not essential for the self-administration of opiates (Schuster and Thompson 1969).

Moreover, a review (McAuliffe 1975a, pp. 374, 382) of relevant 139 research showed that normal human subjects in double-blind experiments under markedly unfavorable conditions were willing to repeat the experience caused by their initial doses of opiate drugs, and that reactions to the drug effects became increasingly favorable with repeated administration.

Thus, in many normal subjects there is sufficient neutrality or favorableness to permit repetition of the initial dose, and favorableness tends to snowball in the course of early repetition.

Finally, evidence from studies by Robins and her associates (Robins and Murphy 1967; Robins et al. 1974a) suggests that the probability of addiction in the case of heroin is considerably greater than that associated with other illicit drugs.

Although surveys (e.g., O’Donnell et al. 1976) show that heroin is the illicit drug least often tried by users, they also show that the percentage of users who become strongly addicted and in need of treatment is greater for heroin than for any of the other major drugs of abuse (Siegel 1973, p. 1259; O’Donnell et al. 1976, pp. 67, 79, 126).

The role of individual differences. Individual differences do, however, play an important part in the addiction process. Animal studies (Deneau 1969; Davis and Nichols 1962) have found that even test animals vary substantially in their conditionability to opiates, and researchers have bred rats (Nichols and Hsiao 1967) and mice (Eriksson and Kiianmaa 1971) to produce marked differences in the animals’ willingness to self-administer opiates.

Furthermore, humans also vary in the effects opiates have on them and in the particular effects they seek from opiates, and these variations appear to have profound effects on subsequent drug-related behavior.

Heroin addicts, strongly oriented toward euphoric effects, use large amounts of the drug and even commit crimes to pay for drugs, whereas physician addicts and iatrogenic addicts, who typically are not interested in attaining euphoria, usually moderate their doses and rarely turn to crime to finance their drug consumption.

These relationships have led one of us to propose that there are two distinct forms of opiate addiction: One has euphoria seeking as a focus, and the other does not (McAuliffe 1979).

CONCLUSION

It is important to stress that operant reinforcement theory is merely the starting point for our theory of opiate addiction, which attempts to specify the connections between and to convey the relative importance of the various psychopharmacological and social variables that bring about initiation, continuation, and termination of illicit use of opiates.

Our theory differs most from other theories that are based mainly or entirely on the avoidance of withdrawal as their source of reinforcement (e.g., Akers 1977; Lindesmith 1947, 1975; Wikler 1965, 1973b) because of the major role it reserves for positive reinforcement from euphoria, and because it considers the overall balance of reinforcement from both the social environment and drugs in motivating abstinence.

Those who continue to question the importance of euphoria (e.g., Akers 1977, p. 101) in addiction because it is not always present on every shot have yet to confront the difference in criminality between euphoria-seeking addicts and other addicts as a factor in determining social importance.

Although barbiturates also cause physical dependence and severe withdrawal symptoms, and although they were also freely available in Southeast Asia, serious morbidity from drug use among U.S. Army enlisted men was confined to the chronic use of heroin, and habituation to barbiturates was infrequent (Siegel 1973, p. 1259; Robins 1974b, 140 pp. 26, 34).

Clearly, there must be more involved in opiate addiction than physical dependence. Although there is also an extensive psychiatric literature that emphasizes self-medicating use of opiates to alter moods as a coping mechanism rather than euphoria (e.g., Duncan 1977; Khantzian et al. 1974; Powell 1973; Sheppard et al. 1972; Weech 1966), euphoria is often mentioned spontaneously in their case histories but not elaborated in their explanations (e.g., Khantzian et al. 1974).

Pleasurable experiences of themselves, moreover, have psychotherapeutic value, so that self-medication need not exclude euphoria even when self-medication does motivate drug use.

As we see it, the more distinguishing features of our theory are its emphasis on the intrinsic reinforcement properties of opiates, especially euphoria; the theory’s conception of addiction as a continuous variable and an insidious process; its attention to and identification of the relevant contingencies and schedules of reinforcement peculiar to opiates and actually governing the behavior of human addicts at various stages of their careers; and its flexibility in being able to distinguish and accommodate the existence of several different types of addict (weekenders, hardcore addicts, euphoria seekers, and medical addicts).

No mere translation of operant conditioning theory could accomplish these various ends. 

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From N.I.D.A. Monograph 30 - Theories on Drug Abuse: Selected Contemporary Perspectives.  [Page for pdf file download, which includes diagrams and reference list.]