Inducing Craving for Alcohol in the Laboratory

by National Institute of Health

Research on the mechanisms of craving often involves inducing craving in subjects in controlled settings. This article describes techniques that have been used to induce craving for alcohol, including exposing subjects to actual alcoholic beverages, exposing subjects to visual representations of alcoholic beverages, manipulating the subjects' mood states, and controlling environmental settings. The intensity of craving can be rated by the subjects themselves or can be assessed by clinicians through behavioral observations or the measurement of certain physiological responses. Success in inducing craving in the laboratory, however, has been inconsistent. Ultimately, researchers may need to monitor subjects' craving responses in actual environmental settings.

Many researchers and clinicians consider craving for alcohol a precursor to relapse among alcoholics in treatment. The role of craving in relapse is controversial, however, and research on the subject is hampered by the lack of a generally accepted definition of craving. Rankin and colleagues defined craving as a "central state," synonymous with a desire or disposition to drink alcohol. Using this approach, craving can be considered a motivational state (a condition that increases the probability of seeking and consuming alcohol or other drugs [AODs]). This does not imply, however, that craving always leads to drinking. Although this definition lacks precision to some extent, it has the advantage of differentiating craving from intention, expectancies, or automatic behaviors ("habit").

Craving may be triggered by exposure to an object, environment, or emotion that a person has come to associate with alcohol consumption. Such stimuli are called alcohol-related cues (ARCs). Ludwig and colleagues suggested that the ability of ARCs to elicit craving may be acquired through a learning process called classical conditioning. This form of learning occurs when a stimulus that would not normally elicit any particular response (a neutral stimulus) is repeatedly associated, or paired, with a stimulus that does elicit a specific response. The previously neutral stimulus is referred to as a cue. Thus, exposure to ARCs may eventually elicit mental, behavioral, and physiological reactions similar to those evoked by the actual consumption of alcohol or by withdrawal. Such cues may include the sight or smell of an alcoholic beverage; the familiar surroundings of a favorite bar; or the onset of an emotional state, such as anger or depression, that a person is accustomed to reacting to by drinking.

Some researchers have explored the possibility of diminishing craving by repeatedly exposing subjects to ARCs without permitting them to drink. Proponents of this approach purport that the procedure can diminish and eventually abolish craving by weakening the association between cue and response.

Research on the mechanisms of craving is required to improve our understanding of the development of alcoholism and to support treatment and prevention efforts. Therefore, researchers have developed techniques to induce craving for alcohol in controlled settings. This article briefly reviews techniques for measuring craving and describes approaches to inducing craving that use the following strategies: exposing subjects to actual alcoholic beverages, exposing subjects to visual representations of alcoholic beverages, manipulating subjects' mood states, and controlling environmental settings.

Measuring Craving

Craving can be measured directly by asking subjects to rate the strength of their urge to drink or indirectly by observing subjects' behavior in response to ARCs or to the consumption of alcohol itself. Craving can also be assessed indirectly by measuring certain physiological responses that appear to accompany craving, such as increased salivation and swallowing. Other measurable physiological responses include changes in heart rate and in the electrical properties of the skin surface.

Exposure to Alcoholic Beverages

The first attempts to elicit craving in the laboratory involved the presentation of those cues considered most likely to evoke an appropriate response (the most salient cues). In the most basic application of this approach, the experimenter places a standard alcoholic drink on a table in front of the subject and instructs the subject to look at the beverage, hold it (at arm's length in some studies), and sniff it repeatedly. To minimize the possibility of provoking relapse, researchers usually instruct alcohol-dependent subjects not to drink the beverage and provide them with no opportunity to consume it.

The effectiveness of this frequently used method for eliciting craving is variable. Although researchers using this approach have found overall increases in self-reported desire to drink, other researchers have noted that reactivity rates are only about 50 to 60 percent (only approximately 50 to 60 percent of subjects report increased craving). This procedure can be rendered more effective by offering the subject his or her choice of alcoholic beverage and by mixing and pouring the drink (or allowing the subject to do so) in the manner to which the subject is accustomed.

Pomerleau and colleagues combined olfactory and visual cues in a series of 5-minute "sniff" trials involving 8 alcoholics in treatment, 10 nonalcoholics, and 2 recovering alcoholics. As a basis for comparison, the subjects were first instructed to sniff cedar chips to determine their reaction to a distinctive but nonalcoholic odor. Each subject subsequently sniffed his or her favorite alcoholic beverage from an open container bearing the manufacturer's label. Aggregate reactivity to alcohol, measured as swallowing and as self-reported craving, was higher among alcohol-dependent subjects than among nonalcoholic subjects. Of the 10 alcoholic participants in this study, 9 showed significantly increased salivation after sniffing alcohol, a reactivity rate of 90 percent. However, only 5 of the 10 alcoholic participants reported subjective increases in craving.

Stormark and colleagues evaluated physiological responses and self-reported craving among alcoholics in treatment and among social drinkers3 exposed to olfactory stimuli. Alcoholic cues included beer and vodka; neutral cues included vanilla and soap. Based on the results of prior testing, these stimuli were further distinguished by the ease with which they could be identified by smell. Neither neutral odors nor the low-potency 4 alcohol odor (vodka) elicited significant differences in physiological reactivity or self-reported craving. However, alcoholic participants showed decreased heart rates in response to the high-potency alcohol odor (beer). This reaction is considered a physiological indicator of the orienting response, in which attention is directed to a novel and potentially important stimulus that may require a response. Alcoholic subjects also reported increased difficulty in their perceived ability to refuse a drink in response to high-potency alcohol odors than did social drinkers. These reactions in the alcoholic subjects are consistent with what would be considered a craving response.

About the Author

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