A Review of the Effects of Perceived Drug Use Opportunity on Self-Reported Urge

Selection of Studies

Both formal and informal approaches were used to search the literature. First, we examined the studies included in Carter and Tiffany’s (1999) review of drug cue reactivity.¹ Additional articles were identified with computer database searches (PsycLIT and Medline) as well as through inspection of reference lists from published journal articles and books. The general criteria for inclusion in the review sample were that (a) the study included a sample with addiction of some type (i.e., alcoholism, smoking, heroin or cocaine addiction); (b) self-reported urge was assessed during a drug cue exposure manipulation; and (c) group means were reported by averaging absolute scores on a self-report urge or craving scale, either in text or figure form. Studies were excluded from the review if participants were taking a medication to reduce cravings (e.g., Hutchison, Monti, et al., 1999; where a medication group was compared to a placebo group, only data from the placebo group were included in the present review, e.g., Kranzler & Bauer, 1992.) Studies also were excluded if they did not describe the numerical endpoints of the urge scale, reported only inferential statistical results without group means, or reported only change scores for self-report urge without the absolute group mean scores. Finally, certain studies (e.g., Monti et al., 1993a; Sayette & Hufford, 1995) were excluded from the review if the self-report urge data were also published in another article already included in the review.

Self-report urge measures often use different terms, such as urge, craving, want, or desire (cf. Kozlowski & Wilkinson, 1987; Sayette et al., 2000). For the purposes of this article, self-reported urge or urge ratings are used to refer to whichever of these items or sets of items were used in each study. In order to compare across studies, urge scores were converted to a percentage of the maximum value of the particular scale (Turkkan, McCaul, & Stitzer, 1989).

Self-Reported Urge Among Continuing Drug Users

Table 1 includes self-reported urge scores during cue exposure for studies involving drug users not seeking treatment at the time of the study. This group of studies includes samples of cigarette smokers, as well as those with active alcoholism and heroin use who were not in treatment. Though the drug was not consumed during the cue exposure manipulation, nothing prevented participants from using their drug immediately following the experiment, which was often less than an hour after cue exposure. As can be seen in Table 1, participants reported robust urges, averaging more than two thirds (69.2%) of the scale maximum. Each study reported mean urge ratings on the top half of its scale.

Reported Urge Among Hospitalized Drug Users Attempting Abstinence

Table 2 presents studies involving drug users in abstinence treatment programs. For these participants, perceived drug use opportunity is considered absent due both to the patients’ putative motivation to maintain abstinence and to their difficulty acquiring drugs in the hospital setting. Patient samples include those with alcoholism as well as those with opiate and cocaine addiction. As depicted in Table 2, participants’ reported urges during drug cue exposure were relatively modest, averaging 37.2% of the scale. Although these samples comprised recently detoxified people with addiction, 12 of the 16 studies reported mean urge scores less than half of the scale maximum, and none reported means in the upper third of the urge scale during drug cue exposure.

Findings from Tables 1 and 2 are consistent with the hypothesis that self-reported urges are higher for people with addiction who have access to the drug following the experiment than for those who do not. Although perceived drug use opportunity appears to influence self-reported urge scores, there are several alternative explanations for the differences found in Tables 1 and 2. First, urge ratings across these two tables may be partly a function of type of addiction. Smoking urge ratings tended to be higher than other types of drug urge ratings. Because smokers participated only in studies listed in Table 1, perceived drug use opportunity is confounded by drug type. Likewise, consistent with Carter and Tiffany’s (1999) conclusions, Table 2 indicates that alcoholic samples reported urges about half as strong as those of the other addict samples. With one exception, alcohol studies were only represented in Table 2. Second, the addicts in treatment settings represented in Table 2 may already have been benefiting from addiction treatment. That is, treatment, rather than perceived drug use opportunity, may have led to lower reported urge scores for those participants. In most cases, though, drug cue exposure data were recorded very early in treatment, often during an initial assessment phase before active treatment commenced (Rohsenow et al., 1994; Rubonis et al., 1994). Third, participants who are enrolled in abstinence treatment programs may be reluctant to report strong urges to use the drug. Participants may fear, for example, that a high urge score might cause clinicians, family members, or employers to worry that the participants will fail to maintain abstinence. The next two sets of studies examine these alternative explanations.

Reported Urge: Those With Addiction Versus Controls

Several studies have compared urge reports of addicted and nonaddicted control participants in response to the same drug cues. Tables 3 and 4 compare those with addiction who perceived that they were free to use the substance during the study with those who did not have access to the drug during or following cue exposure. All but one study in Tables 3 and 4 included as the sample people with addiction who were then in treatment.

Table 3 lists studies in which both those with alcoholism and social drinkers believed that they could drink alcohol following cue exposure. In each study, the alcoholic group reported higher urges to drink than did the nonalcoholic control group. This finding is consistent with most urge theories, which posit that drug use history affects urge strength (e.g., Ludwig, Wikler, & Stark, 1974; Robinson & Berridge, 1993; Siegel, 1983; Solomon & Corbit, 1973; Stewart, de Wit, & Eikelboom, 1984). From a conditioning perspective, for example, heavy drinkers pair alcohol cues with consumption more often than do lighter drinkers and thus are more susceptible to conditioned withdrawal (craving) during a cue exposure manipulation (Ludwig, Wikler, & Stark, 1974). Similar to the data reported in Table 1, the average urge ratings for those with alcoholism expecting to drink was two thirds (67.0%) of the scale maximum. Table 3 shows that when those with alcoholism perceived an opportunity to drink, their urge reports were higher than those of social drinkers, even if the people with alcoholism were receiving treatment.

In contrast to the findings from Table 3, Table 4 shows that when there was not a perceived opportunity to drink (i.e., alcohol could not be consumed following cue exposure), inpatients with alcoholism did not consistently report higher urges to drink than nonalcoholics. In these studies, only the nonpatient control drinkers had a perceived opportunity to use alcohol following the experiment. Only one of the six studies in Table 4 reported significantly higher urge scores for participants with alcoholism than for controls, whereas one study (Cooney, Gillespie, Baker, & Kaplan, 1987) actually found the opposite pattern, with controls reporting higher urges than participants with alcoholism. These findings run counter to prevailing theories (e.g., Ludwig et al., 1974; Robinson & Berridge, 1993; Siegel, 1983; Solomon & Corbit, 1973; Stewart et al., 1984), which posit that people with alcoholism should experience greater cravings than nonaddicted drinkers. Unlike the studies listed in Table 3, the mean reported urge score for those with addiction in Table 4 fell on the lower half (48.5%) of the urge ratings. These findings with people with alcoholism suggest that differences in Tables 1 and 2 are not due exclusively to smokers’ reporting high urges or participants with alcoholism reporting low urges. Table 3 clearly shows that being in treatment does not preclude strong urge ratings. Indeed, the mean urge ratings for the alcoholic samples in Table 3 were similar to those for the nonpatient samples listed in Table 1.

Taken together with the findings from the first two tables, Tables 3 and 4 suggest that perceived opportunity to use a drug affects urge ratings. Nevertheless, the studies examined were not designed specifically to test the impact of perceived opportunity to use on reported urge. Moreover, not all data from Tables 1-4 conformed to our predictions. For example, although both alcoholic groups in Tables 2 and 4 were unable to drink, their urge ratings differed. Especially relevant to the present analysis were studies that experimentally manipulated perceived drug use opportunity within a single experiment.

Reported Urge in Studies That Manipulated Perceived Drug Use Opportunity

Table 5 lists experiments that manipulated perceived opportunity to use. These studies were especially relevant to the importance of perceived drug use opportunity because they held constant factors such as treatment status, type of drug, and motivation to quit. In three of the studies, perceived drug use opportunity was a between-subjects variable. In the perceived drug use opportunity conditions, participants in these studies expected to use or experience the drug’s effects during the experiment, whereas in the no-opportunity conditions they were unable to use or experience the drug for at least several hours. The remaining two studies (Carter & Tiffany, 2000; Dols, Willems, van den Hout, & Bittoun, 2000) employed a within-subject design in which perceived drug use opportunity was manipulated across multiple cue exposure trials. All five studies found significantly higher drug urges when there was a perceived opportunity to use the drug than when there was not. In conjunction with the studies listed in Tables 1-4, these experiments support the proposition that perceived drug use opportunity affects self-reported urge.²

Urge Versus Urge Report

The data reviewed thus far suggest that perceived drug use opportunity affects self-reported urge. Although it is customary to assume that craving can be indexed through self-report measures, such ratings do not provide a direct readout of a person’s craving state. That is, a self-report instrument is unlikely to provide a one-to-one mapping of verbal report to hypothetical internal state (Sayette et al., 2000). Craving instead may be viewed as a construct best understood through multidimensional assessment (Baker, Morse, & Sherman, 1987; Rankin, Hodgson, & Stockwell, 1979). Examination of nonverbal indices in cue exposure studies provides a means for assessing the scope of the impact of perceived drug use opportunity. Specifically, it is important to determine whether response modalities other than self-report suggest that cue reactivity is strengthened when addicts perceive an opportunity to use the drug following cue exposure.³

Both nonverbal and self-report measures detect significant increases in reactivity during drug cue exposures (see Carter & Tiffany, 1999). Although the studies listed in Tables 2 and 4 revealed lower than expected urge ratings, nearly all (91%) of them still showed significant increases from baseline. In Tables 1-4, the importance of perceived drug use opportunity emerges in the percent maximum of scale. Scores of nonverbal measures of cue reactivity, unlike those of self-report, are not readily transformed to a percentage of a scale maximum. For instance, the knowledge itself that a particular cue exposure manipulation led to a significant increase in heart rate for one group is hard to interpret. Nonverbal measures can be evaluated, however, if a study is explicitly designed to manipulate perceived drug use opportunity.

Only three studies manipulating perceived drug use opportunity included nonverbal measures. Two employed psychophysiological measures and one relied on a cognitive performance measure. The former provided evidence that perceived drug use opportunity led to generally greater psychophysiological reactivity than when drug use opportunity was not perceived (Carter & Tiffany, 2000; Laberg, 1986). In contrast, the study using a cognitive performance measure (secondary response time latency to an auditory probe) found response time to be greater when participants did not have a perceived drug use opportunity than when they did (Juliano & Brandon, 1998). This latter study is also of interest in that self-reported urge was greater among the smokers who perceived an opportunity to smoke than those who did not. More research is needed to determine with confidence which measures, along with self-report, are sensitive to perceived drug use opportunity.

Urge Versus Cue-Specific Urge

Researchers often examine cue reactivity by partialing out responses during a control cue before examining drug cue reactivity (Carter & Tiffany, 1999). Whether to adjust for urge ratings during control cue exposure before interpreting urge ratings during drug cue reactivity is a complex issue, and in some cases adjusting may not be the most appropriate way to assess the effects of craving manipulations (Sayette et al., 2000). Whether or not the effect of perceived drug use opportunity is specific to drug cues may depend on the experimental design. If the drug use opportunity manipulation is provided prior to control cue exposure, then urge ratings may differ even during control cue exposure. For instance, among studies in Tables 1 and 2, in which perceived drug use opportunity was understood from the outset, urge rating differences emerged during control exposure (mean urge ratings were 46% and 15% of scale maximum, respectively, for those who did and those who did not perceive the opportunity to use). Similar conclusions can be drawn from the studies in Tables 3 and 4 that included control cues. Specifically, when drinking was permitted, participants with alcoholism reported greater urges than did social drinkers during control exposure (McCaul, Turkkan, & Stitzer, 1989). In addition, among the six studies in Table 4, in which drug use was prevented, reported urge during control exposure was similar for those with alcoholism (M = 26%) and social drinkers (M = 23%).

In contrast, the two studies in Table 5 that included control cues suggest perceived drug use opportunity effects are enhanced during drug cue exposure. In one, control cue urge ratings, recorded as change from baseline, increased by .40 in the expect-to-smoke condition and by .18 in the expect-not-to-smoke condition (Juliano & Brandon, 1998). This study also found, however, that the effect of perceived drug use opportunity was greater during drug cue exposure. Likewise, Carter and Tiffany (2000) reported that the effect of drug availability was specific to drug cue. Future research is needed to clarify the conditions under which the effect of perceived drug use opportunity on urge ratings is specific to drug cue exposure manipulations.

Potential Mechanisms Underlying Effects of Perceived Drug Use Opportunity

Conclusions

There is little doubt that drug cue exposure leads addicts to report strong increases in craving (Carter & Tiffany, 1999). It also appears that perceived drug use opportunity contributes to the degree of craving reported. Specifically, perceived opportunity to use enhances urge reports, though circumstances may exist in which the reverse could be true (Baker et al., 1987; Carter & Tiffany, 2000). Perceived drug use opportunity often has been neglected in cue exposure experiments. Appreciation for the importance of this factor may prove useful across a number of research domains. For example, with increasing interest in the neurobiology of craving (e.g., Breiter & Rosen, 1999), imaging studies may reveal different patterns of neural activity depending on perceived drug use opportunity of the participants.

Investigators interested in personality variables should consider craving a rich concept for investigation (e.g., Bradizza et al., 1999). Our use of the concept of perceived drug use opportunity, rather than drug availability, raises questions about which individual difference factors might influence drug cue appraisal during exposure studies. Lazarus and Folkman (1984) propose that differences in people’s commitments (what is important to them) and beliefs (e.g., about personal control) influence stress appraisals, and these person-level factors also may affect appraisals of craving. Measurement of craving may even include an implicit assessment of coping appraisal; that is, appraisal of craving may reflect an appraisal of what one plans to do about it. The experience of urge may be stronger if one anticipates consuming the substance than if one does not.

Perceiving an opportunity to use a drug may also dictate qualitatively different craving experiences (Baker et al., 1987). Comparing urge ratings of addicts before and after quitting, for example, may require greater sensitivity to the meaning of craving at each period, which may help interpret the apparently counterintuitive finding that cravings prior to quitting tend to be higher than those experienced after quitting (Shiffman et al., 1997). More generally, this review makes clear that clinical researchers should not be surprised by their patients’ relatively low urge reports.

Increased attention to perceived drug use opportunity presents methodological challenges. With a few exceptions, participants in cue-exposure studies do not perceive that they will have an opportunity to consume the drug. Even when availability exists, the procedure typically is arranged such that drug use does not occur for at least several minutes. Carter and Tiffany (2000) distinguish between local and distal availability, the former referring to opportunity for drug use during a cue exposure session and the latter, to drug access following the experiment. Although the boundaries between local and distal availability are open to interpretation, this distinction is likely to produce meaningful differences in evaluating the experience of craving. Recent efforts (e.g., Carter & Tiffany, 2000; Dols et al., 2000) permit manipulation of local availability by exposing those with addiction to repeated trials of drug or neutral cues; for example, sometimes participants are free to use small amounts of the substance (e.g., one cigarette puff) during cue exposure, whereas at other times drug access is uncertain or prohibited. The development of such protocols, which permit local availability while allowing adequate time for craving assessment, remains an important area for research.

Progressive ratio reinforcement schedules also have been used to gauge drug use motivation under multiple conditions during a single session (Rusted, Mackee, Williams, & Willner, 1998). In this paradigm, participants perform a specified amount of work (e.g., engaging in a repetitive computer task) to earn access to the drug, such as a cigarette puff. With each reinforcement, the amount of work required increases progressively. Thus, access to the drug changes continually (becoming more difficult), which arguably permits further evaluation of the importance of perceived drug use opportunity, if urge is assessed during each trial. A potential concern with cue exposure designs that involve repeated opportunities for drug use (e.g., the progressive ratio experiments and Carter and Tiffany’s, 2000, cue availability paradigm) is that initial opportunities to use the drug during the experiment may alter motivation for the drug in subsequent trials (Sanders, 2000). For example, if smokers already have been able to receive six puffs of a cigarette, by the seventh trial they may be less eager to smoke. Such a concern has led some to modify the progressive ratio design so that no drug use occurs until the end of the study (Grobe & Perkins, 1999). This modified progressive ratio design does not permit local availability.

One reason that local availability has rarely been manipulated in cue-exposure studies is that it may be difficult to execute, particularly if the cue reactivity measures take a while to complete. It is unclear how long those with addiction who are informed they will be able to use the drug soon can be exposed to drug cues before they become impatient or frustrated because “soon” is not soon enough. Nevertheless, the importance of examining perceived drug use opportunity from both local and distal perspectives mandates efforts to develop new experimental paradigms. Research to develop ways to extend the duration of local availability, for example, would be useful. Such approaches promise to improve understanding of the role of perceived drug use opportunity in urge responding and, in turn, should promote greater appreciation for the role of drug craving in addiction.