Craving: Approaching Avoidance : Part 2

by National Institute of Health

(Page 2 of 7)

The Role of Historical Factors

Influences termed "historical factors" contribute to the decisionmaking process. Such factors can shape a person's drinking experiences and his or her subsequent inclination to consume alcohol. For example, genetically based aspects of individual biochemical reactivity can contribute to intrinsically pleasant (euphoric) or unpleasant (flushing) effects precipitated by alcohol consumption. The strength of certain personality characteristics, such as antisociality (a tendency toward aggressive or criminal behavior) and sensation seeking (a strong predilection for novel and risky experiences), have also been implicated in the associated risk for alcoholism. External factors, such as sociocultural drinking norms and personal experiences with alcohol-related consequences, can also support, inhibit, or modulate the use of alcohol and influence drinking behavior.

Thus, biochemical reactivity, personality characteristics, the sociocultural environment, and personal experience of drinking outcomes help determine a person's response to ARCs. However, the above-mentioned factors are not necessarily internally consistent or static. Consequently, a person's responses to ARCs often represent a fusion of attractions and repulsions, both within a particular set of circumstances and across time. This can, of course, contribute to ambivalence.

Excessive drinkers tend to develop more marked "conditioned" responses to cues (the smell of alcohol or perhaps a certain mood) that have been repeatedly associated with drinking. In other words, exposure to such cues can elicit physiological, emotional, and cognitive reactions, including those that constitute "craving." Several influential conditioning models have been advanced to explain the relationships among ARC exposure, craving, and subsequent alcohol consumption, particularly in alcoholics. These models have been extensively reviewed elsewhere in the literature; a full description of each of these models is beyond the scope of this article.

However, all conditioning models posit that ARCs ultimately elicit a craving response that motivates further alcohol use. Each such model accounts for approach inclination (craving) in terms of the action of two interrelated learning processes: the association of previously neutral stimuli with alcohol consumption and the subsequent connection of these cues with certain reinforcing actions of alcohol that encourage future indulgence in drinking. Such models diverge from one another mainly with respect to the mechanisms by which alcohol cues are presumed to motivate alcohol use. In particular, each model offers different descriptions of the reactions elicited by alcohol cues.

Some conditioning models hypothesize that ARCs stimulate an aversive state (elicit subclinical withdrawal symptoms or negative emotional responses associated with deprivation) that lies behind craving and the desire to drink. Other conditioning models suggest that alcohol cues stimulate an appetitive state by signaling access to desirable effects (euphoria) through drinking. In the first instance, craving or motivation to drink is described as a desire to obtain relief from an aversive state (negative reinforcement); in the second instance, craving is viewed as a desire to experience the pleasurable effects of alcohol intoxication (positive reinforcement). A hybrid model involves speculation that cues can elicit both types of motives or craving. In any event, these models predict a similar outcome: Exposure to ARCs should increase the inclination to "approach" alcoholic beverages.

Although these models have provided a rich theoretical foundation for the initial study of craving and other reactions to alcohol cues, they do not address the potential elicitation of avoidance inclinations by the same cues. Moreover, no existing model can adequately account for all of the evidence on craving accumulated thus far. Recent developments in neuropsychopharmacology appear to address at least some of these shortcomings by providing potentially important building blocks for the construction of a more complete picture of the development and operation of craving. In particular, advances in this arena have yielded valuable information about the specific effects of AODs and AOD-relevant stimuli on brain systems and have offered suggestions about the possible impact of these effects on subsequent behavior.

For example, Robinson and Berridge have highlighted the importance of "neuroadaptation," or sensitization, of certain brain systems due to repeated substance use. Their theory takes a step toward the integration of biological and learning processes into a more comprehensive model of craving. This analysis holds that psychoactive substance use, especially by relatively inexperienced consumers, can produce a pleasant affective response by stimulating neural systems associated with reward. This is regarded as a simple "liking" for the effects of the substance and can motivate further use.

Robinson and Berridge further posit that the reinforcing effects of AODs do not maintain long-term substance use by addicts. Rather, these two researchers assert and provide evidence suggesting that the more compulsive "wanting" of the substance may result from repeated substance use that provokes a specific neuroadaptation - that is, the progressive and persistent hypersensitization of the dopamine pathways implicated in the mediation of wanting or craving the substance. The theory specifically segregates the mechanisms responsible for "liking" (based on simple positive reinforcement) from the mechanisms underlying "wanting" (sensitization to cues associated with the substance).

This distinction enables the model to account for the continued use of AODs even when the subjective pleasure derived from them has disappeared or diminished greatly, as is often the case for addicts. A key element of this model is its proposition that the hypothesized neuroadaptation, or sensitization, is influenced by associative learning processes in such a way that exposure to cues which have been reliably paired with substance use enables the cues themselves to stimulate sensitization and thereby increase and sustain "wanting" for the substance. Hence, craving is viewed as involving both biochemical and learning processes.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.