Similar consumption and responding across single and multiple sources of drug

Using the Cigarette Purchase Task to examine the relative reinforcing value of cigarettes among mothers with versus without opioid dependence

The Cigarette Purchase Task (CPT), in which participants estimate the number of cigarettes they would smoke across increasing cigarette prices, measures the relative reinforcing value of cigarettes. Although opioid-dependent individuals are particularly vulnerable to tobacco addiction, more research is needed to elucidate whether and to what extent their motivation to smoke differs from not-opioid-dependent smokers controlling for potential sociodemographic differences. Participants were 173 women (65 opioid-dependent) in an ongoing clinical trial for smoking cessation. Baseline CPT responses were compared between opioid-dependent and not-opioid-dependent women using five demand indices: Demand Intensity; O_max; P_max; Breakpoint (BP); and α, and two latent factors: Amplitude and Persistence. Final regression models adjusted for sociodemographic characteristics differing between the two groups. Opioid-dependent women had greater demand Intensity (i.e., number of cigarettes they would smoke if they were free) than not-opioid dependent women in the adjusted model, F(1, 156) = 6.93, p = .016. No other demand indices differed significantly. Regarding latent factors, demand Amplitude (i.e., volumetric consumption), but not Persistence (i.e., price insensitivity), was greater for opioid-dependent women in the adjusted model, F(1, 146) = 4.04, p = .046. These results further demonstrate that the CPT is a highly sensitive task that can illuminate potentially important individual and population differences in the relative reinforcing value of smoking. Greater demand Intensity and Amplitude differentiated smokers with comorbid opioid dependence; thus, decreasing smoking prevalence among opioid-dependent populations may require policies and interventions that can decrease cigarette demand Intensity and Amplitude. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Comparing participant estimated demand intensity on the cigarette Purchase Task to consumption when usual-brand cigarettes were provided free

Accumulating evidence suggests that the hypothetical Cigarette Purchase Task (CPT), especially its demand Intensity index (i.e., estimated cigarettes participants would smoke if free), is associated with individual differences in smoking risk. Nevertheless, few studies have examined the extent to which hypothetical CPT demand Intensity may differ from consumption when participants are provided with free cigarettes. That topic is the overarching focus of the present study. Participants were 745 adult smokers with co-morbid psychiatric conditions or socioeconomic disadvantage. CPT was administered for usual-brand cigarettes prior to providing participants with seven days of their usual-brand cigarettes free of cost and consumption was recorded daily via an Interactive Voice Response (IVR) System. Demand Intensity was correlated with IVR smoking rate (rs 0.670-0.696, ps < 0.001) but estimates consistently exceeded IVR smoking rates by an average of 4.4 cigarettes per day (ps < 0.001). Importantly, both measures were comparably sensitive to discerning well-established differences in smoking risk, including greater cigarettes per day among men versus women (F(1,732) = 18.74, p < 0.001), those with versus without opioid-dependence (F(1,732) = 168.37, p < 0.001), younger versus older adults (F(2,730) = 32.93, p < 0.001), and those with lower versus greater educational attainment (F(1,732) = 38.26, p < 0.001). Overall, CPT demand Intensity appears to overestimate consumption rates relative to those observed when participants are provided with free cigarettes, but those deviations are systematic (i.e., consistent in magnitude and direction, Fs all <1.63; ps > 0.19 for all interactions with subgroups). This suggests that demand Intensity was sensitive to established group differences in smoking rate, supporting its utility as an important measure of addiction potential.

Examining effects of unit price on preference for reduced nicotine content cigarettes and smoking rate

Cigarette preference increases as a function of greater nicotine content, but manipulating cost can shift preference. The aims of the present study are to model whether (1) the behavioral-economic metric unit price (cost/reinforcer magnitude) accounts for preference shifts and (2) whether preference shifts toward reduced nicotine content are associated with smoking reductions. In a multisite study between 2015 and 2016, 169 daily smokers from vulnerable populations completed two concurrent-choice conditions examining preference for smoking normal (15.8 mg/g) and reduced (0.4 mg/g) nicotine content cigarettes. In Condition 1, both products were available at 10 responses/choice. In Condition 2, availability of the 0.4 mg/g dose remained at 10 responses/choice while the 15.8 mg/g dose was available on a progressive-ratio (PR) schedule wherein response cost increased following each choice. Unit prices were calculated by dividing dose by response requirement. Results were analyzed using ANOVA and binomial tests (p < .05). Participants preferred the 15.8 over 0.4 mg/g dose in Condition 1, but shifted preference to the 0.4 mg/g dose in Condition 2 (p < .001) immediately before the point in the PR progression where unit price for 15.8 dose exceeded unit price for the 0.4 dose (p < .001). This shift was associated with a reduction in smoking (p < .001). The unit price of nicotine appears to underpin cigarette product preference and may provide a metric for predicting preference and potentially impacting it through tobacco regulations. These results also demonstrate that reduced compared to normal nicotine content cigarettes sustain lower smoking rates discernible even under acute laboratory conditions and in vulnerable populations.

Examining interrelationships between the Cigarette Purchase Task and delay discounting among pregnant women

Two common behavioral economic simulation tasks used to study cigarette smoking are the Cigarette Purchase Task, a measure of cigarette demand, and delay discounting, a measure of the subjective value of rewards as a function of delays to delivery. Few studies have evaluated whether combining these tasks enhances understanding of smoking beyond either alone. The current study represents an initial evaluation of the intersection between cigarette demand indices and delay discounting among pregnant smokers by examining associations between these measures and whether a woman makes antepartum quit attempts before entering prenatal care (a reliable predictor of eventual quitting). Participants were 159 pregnant women enrolled in a smoking-cessation trial. Low O max and shallow discounting were each associated with antepartum quit attempts. Participants were next categorized into four subgroups (low O max , shallow discounting; low O max , steep discounting; high O max , shallow discounting; high O max , steep discounting) using median splits. Those with shallow discounting and low O max were more likely to have made quit attempts than each of the other three subgroups. That is, steep discounting appears to undermine the association of low O max and efforts to quit smoking during pregnancy while high O max overshadows any protective influence associated with shallow discounting.

Simulating demand for cigarettes among pregnant women: A Low-Risk method for studying vulnerable populations

A substantive obstacle to experimentally studying cigarette smoking and use of other tobacco products in pregnant women is the risk of adverse effects on mother and fetus from experimenter administration of the product of interest. The purpose of this study is to investigate bypassing that obstacle by using behavioral economic simulation tasks. In the present study we used the Cigarette Purchase Task (CPT) to simulate changes in demand for hypothetical cigarettes as a function of varying cigarette prices. Participants were 95 pregnant women who completed the CPT prior to participation in a smoking-cessation trial. Aggregate and individual participant demand varied as an orderly function of price and those changes were well fitted by an exponential equation. Demand also varied in correspondence to two well-validated predictors of individual differences in smoking cessation among pregnant women (cigarettes smoked per day, pre-pregnancy quit attempts). Moreover, CPT indices were more effective than these two conventional variables in predicting individual differences in whether women made a quit attempt during the current pregnancy. Overall, these results represent a promising step in demonstrating the validity and utility of the CPT for experimentally examining demand for cigarettes, and potentially other tobacco and nicotine delivery products, among pregnant women.

Demand curves for hypothetical cocaine in cocaine-dependent individuals

RATIONALE

Drug purchasing tasks have been successfully used to examine demand for hypothetical consumption of abused drugs including heroin, nicotine, and alcohol. In these tasks, drug users make hypothetical choices whether to buy drugs, and if so, at what quantity, at various potential prices. These tasks allow for behavioral economic assessment of that drug's intensity of demand (preferred level of consumption at extremely low prices) and demand elasticity (sensitivity of consumption to price), among other metrics. However, a purchasing task for cocaine in cocaine-dependent individuals has not been investigated.

OBJECTIVES

This study examined a novel Cocaine Purchasing Task and the relation between resulting demand metrics and self-reported cocaine use data.

METHODS

Participants completed a questionnaire assessing hypothetical purchases of cocaine units at prices ranging from $0.01 to $1,000. Demand curves were generated from responses on the Cocaine Purchasing Task. Correlations compared metrics from the demand curve to measures of real-world cocaine use.

RESULTS

Group and individual data were well modeled by a demand curve function. The validity of the Cocaine Purchasing Task was supported by a significant correlation between the demand curve metrics of demand intensity and O max (determined from Cocaine Purchasing Task data) and self-reported measures of cocaine use. Partial correlations revealed that after controlling for demand intensity, demand elasticity and the related measure, P max, were significantly correlated with real-world cocaine use.

CONCLUSIONS

Results indicate that the Cocaine Purchasing Task produces orderly demand curve data, and that these data relate to real-world measures of cocaine use.

Effects of varenicline on abstinence and smoking reward following a programmed lapse

INTRODUCTION

Varenicline (Chantix®) is an efficacious first-line medication for smoking cessation. Studies suggest that one mechanism by which varenicline facilitates sustained smoking abstinence is by reducing the likelihood of relapse to smoking when a lapse, or slip, occurs during a quit attempt. The present study extends this line of research by conducting a prospective laboratory study to examine the relapse prevention effects of varenicline following a programmed lapse.

METHODS

Daily smokers (N = 47) completed a 5-week outpatient study in which they were randomized to receive varenicline or placebo. The first week was a medication induction period that was immediately followed by a 4-week quit attempt. A programmed lapse (2 cigarettes smoked in the laboratory) occurred on the second day of the quit attempt.

RESULTS

Participants receiving varenicline were slower to relapse and had greater total abstinence rates following lapse exposure. Participants in the varenicline group rated lapse cigarettes lower on measures of reward and intoxication and showed increased behavioral economic demand elasticity for cigarettes (reduced cigarette purchasing at higher prices) compared with those receiving placebo.

CONCLUSIONS

These results demonstrate a relapse prevention effect of varenicline following smoking lapse exposure and suggest that an attenuation of reward from smoking and the blunting of subjective effects of smoking may underlie and/or contribute to this effect.

Human nicotine conditioning requires explicit contingency knowledge: is addictive behaviour cognitively mediated?

RATIONALE

Two seemingly contrary theories describe the learning mechanisms that mediate human addictive behaviour. According to the classical incentive theories of addiction, addictive behaviour is motivated by a Pavlovian conditioned appetitive emotional response elicited by drug-paired stimuli. Expectancy theory, on the other hand, argues that addictive behaviour is mediated by an expectancy of the drug imparted by cognitive knowledge of the Pavlovian (predictive) contingency between stimuli (S+) and the drug and of the instrumental (causal) contingency between instrumental behaviour and the drug.

AIMS AND METHOD

The present paper reviewed human-nicotine-conditioning studies to assess the role of appetitive emotional conditioning and explicit contingency knowledge in mediating addictive behaviour.

RESULTS

The studies reviewed here provided evidence for both the emotional conditioning and the expectancy accounts. The first source of evidence is that nicotine-paired S+ elicit an appetitive emotional conditioned response (CR), albeit only in participants who expect nicotine. Furthermore, the magnitude of this emotional state is modulated by nicotine deprivation/satiation. However, the causal status of the emotional response in driving other forms of conditioned behaviour remains undemonstrated. The second source of evidence is that other nicotine CRs, including physiological responses, self-administration, attentional bias and subjective craving, are also dependent on participants possessing explicit knowledge of the Pavlovian contingencies arranged in the experiment. In addition, several of the nicotine CRs can be brought about or modified by instructed contingency knowledge, demonstrating the causal status of this knowledge.

CONCLUSIONS

Collectively, these data suggest that human nicotine conditioned effects are mediated by an explicit expectancy of the drug coupled with an appetitive emotional response that reflects the positive biological value of the drug. The implication of this conclusion is that treatments designed to modify the expected value of the drug may prove effective.

Unit price and choice in a token-reinforcement context

Pigeons were exposed to multiple and concurrent second-order schedules of token reinforcement, with stimulus lights serving as token reinforcers. Tokens were produced and exchanged for food according to various fixed-ratio schedules, yielding equal and unequal unit prices (responses per unit food delivery). On one schedule (termed the standard schedule), the unit price was held constant across conditions. On a second schedule (the alternative schedule), the unit price was either the same or different from the standard. Under conditions with unequal unit prices, near-exclusive preference for the lower unit price was obtained. Under conditions with equal unit prices, the direction and degree of preference depended on ratio size (number of responses per exchange period). When this ratio differed, strong preferences for the smaller ratio were observed. When this ratio was equal, preferences were nearer indifference. Response rates on the multiple schedule were generally consistent with the preference data in showing sensitivity to ratio size. Results are discussed in terms of a unit-price model that includes handling and reinforcer immediacy as additional costs. On the whole, results show that preferences were determined primarily by delay to the exchange period.

Three predictions of the economic concept of unit price in a choice context

Economic theory makes three predictions about consumption and response output in a choice situation: (a) When plotted on logarithmic coordinates, total consumption (i.e., summed across concurrent sources of reinforcement) should be a positively decelerating function, and total response output should be a bitonic function of unit price increases; (b) total consumption and response output should be determined by the value of the unit price ratio, independent of its cost and benefit components; and (c) when a reinforcer is available at the same unit price across all sources of reinforcement, consumption should be equal between these sources. These predictions were assessed in human cigarette smokers who earned cigarette puffs in a two-choice situation at a range of unit prices. In some sessions, smokers chose between different amounts of puffs, both available at identical unit prices. Individual subjects' data supported the first two predictions but failed to support the third. Instead, at low unit prices, the relatively larger reinforcer (and larger response requirement) was preferred, whereas at high unit prices, the smaller reinforcer (and smaller response requirement) was preferred. An expansion of unit price is proposed in which handling costs and the discounted value of reinforcers available according to ratio schedules are incorporated.