Demand curves for hypothetical cocaine in cocaine-dependent individuals

A sequential multiple assignment randomized trial for cocaine cessation and relapse prevention: Tailoring treatment to the individual

Drug addiction is a chronic, devastating, but treatable disorder. A core principle of drug addiction treatment states that no single treatment is appropriate for everyone (NIDA, 2012); treatments need to adjust based on patient characteristics and response in order to be maximally effective. For cocaine use disorders (CUD), specifically, the most potent intervention currently available for initiating abstinence is behavior therapy using contingency management (CM) procedures, with early cessation being a robust predictor of future abstinence. This raises two key questions for treatment development research: First, can we significantly improve initial CM response rates with targeted adjunctive interventions? Second, for individuals who fail to achieve initial abstinence with CM, is pharmacotherapy an effective augmentation strategy? This paper describes how a sequential, multiple assignment, randomized trial (SMART) design has advantages over a fixed-intervention approach when it comes to collecting data needed to answer both questions. The first aim will examine whether Acceptance and Commitment Therapy (ACT) in combination with CM increases initial abstinence response rates (i.e., 2 consecutive weeks of cocaine-negative urine screens). The second aim will examine whether ACT+CM in combination with modafinil promotes abstinence achievement in initial non-responders. Results are expected to inform how we tailor treatment of CUD to maximize outcomes.

Clinical models of decision making in addiction

As research on decision making in addiction accumulates, it is increasingly clear that decision-making processes are dysfunctional in addiction and that this dysfunction may be fundamental to the initiation and maintenance of addictive behavior. How drug-dependent individuals value and choose among drug and nondrug rewards is consistently different from non-dependent individuals. The present review focuses on the assessment of decision-making in addiction. We cover the common behavioral tasks that have shown to be fruitful in decision-making research and highlight analytical and graphical considerations, when available, to facilitate comparisons within and among studies. Delay discounting tasks, drug demand tasks, drug choice tasks, the Iowa Gambling Task, and the Balloon Analogue Risk Task are included.

Binary components of food reinforcement: Amplitude and persistence

BACKGROUND

Demand curves provide an index of how reinforcing a food is. Research examining the latent structure of alcohol and tobacco reinforcement identified two underlying components of reinforcement, amplitude and persistence. No research has assessed latent structure of food reinforcement and how these factors are related to BMI.

SUBJECTS AND METHODS

Participants were 297 adults from two studies that completed food purchasing tasks to assess the following measures of relative reinforcing efficacy (RRE) of food: intensity (Q₀): purchases made when the food was free or of very minimal price, O_max: maximum expenditure (purchases*price), P_max: price point where maximum expenditure was observed, breakpoint: first price where 0 purchases are made, and demand elasticity (α): quantitative non-linear relationship between purchasing and price. Principal components analysis was used to examine the factor structure of RRE for food across samples and types of food.

RESULTS

Both studies revealed two factor solutions, with P_max, O_max, breakpoint and α loading on factor 1 (persistence) and intensity (Q₀) loading on factor 2 (amplitude) across both high and low energy dense foods. Persistence reflects an aggregate measure of price sensitivity and amplitude reflects the preferred volume of consumption (how long vs. how much). The two factors accounted for between 91.7 and 95.4% of the variance in food reinforcement. Intensity for high energy dense foods predicted BMI for both studies (r = 0.18 and r = 0.22, p's < 0.05).

CONCLUSIONS

The latent factor structure was similar across two significantly different independent samples and across low and high energy dense snack foods. In addition, the amplitude of the demand curve, but not persistence, was related to BMI. These results suggest specific aspects of food reinforcement that can be targeted to alter food intake.

Behavioral economic substitutability of e-cigarettes, tobacco cigarettes, and nicotine gum

The public health impact of e-cigarettes may depend on their substitutability for tobacco cigarettes. Dual users of e-cigarettes and tobacco cigarettes completed purchasing tasks in which they specified daily use levels under hypothetical conditions that varied the availability and price of e-cigarettes, tobacco cigarettes, and nicotine gum (for those with nicotine gum experience). When either e-cigarettes or tobacco cigarettes were the only available commodity, as price per puff increased, purchasing decreased, revealing similar reinforcement profiles. When available concurrently, as the price of tobacco puffs increased, purchasing of tobacco puffs decreased while purchasing of fixed-price e-cigarette puffs increased. Among those with nicotine gum experience, when the price of tobacco puffs was closest to the actual market value of tobacco puffs, e-cigarette availability decreased median tobacco puff purchases by 44% compared to when tobacco was available alone. In contrast, nicotine gum availability caused no decrease in tobacco puff purchases. E-cigarettes may serve as a behavioral economic substitute for tobacco cigarettes, and may be a superior substitute compared to nicotine gum in their ability to decrease tobacco use. Although important questions remain regarding the health impacts of e-cigarettes, these data are consistent with the possibility that e-cigarettes may serve as smoking cessation/reduction aids.

Inhibiting subthalamic nucleus decreases cocaine demand and relapse: therapeutic potential

Preclinical evidence indicates that inactivation of subthalamic nucleus (STN) may be effective for treating cocaine addiction, and therapies that target STN, e.g. deep brain stimulation, are available indicating that this may have clinical promise. Here, we assessed the therapeutic potential of STN inactivation using a translationally relevant economic approach that quantitatively describes drug-taking behavior, and tested these results with drug-seeking tasks. Economic demand for cocaine was assessed in rats (n = 11) using a within-session threshold procedure in which cocaine price (responses/mg cocaine) was sequentially increased throughout the session. Cocaine demand was assessed in this manner immediately after bilateral microinfusions into STN of either vehicle (artificial cerebrospinal fluid) or the GABAA receptor agonist muscimol. A separate group of animals (n = 8) was tested for changes in cocaine seeking either during extinction or in response to cocaine-associated cues. Muscimol-induced inhibition of STN significantly attenuated cocaine consumption at high prices, drug seeking during extinction and cued reinstatement of cocaine seeking. In contrast, STN inhibition did not reduce cocaine consumption at low prices or locomotor activity. Thus, STN inactivation reduced economic demand for cocaine and multiple measures of drug seeking during extinction. In view of the association between economic demand and addiction severity in both rat and human, these results indicate that STN inactivation has substantial clinical potential for treatment of cocaine addiction.

Further examination of the temporal stability of alcohol demand

Demand, or the amount of a substance consumed as a function of price, is a central dependent measure in behavioral economic research and represents the relative valuation of a substance. Although demand is often utilized as an index of substance use severity and is assumed to be relatively stable, recent experimental and clinical research has identified conditions in which demand can be manipulated, such as through craving and stress inductions, and treatment. Our study examines the 1-month reliability of the alcohol purchase task in a sample of heavy drinking college students. We also analyzed reliability in subgroup of individuals whose consumption decreased, increased, or stayed the same over the 1-month period, and in individuals with moderate/severe Alcohol Use Disorder (AUD) vs. those with no/mild AUD. Reliability was moderate in the full sample, high in the group with stable consumption, and did not differ appreciably between AUD groups. Observed indices and indices derived from an exponentiated equation (Koffarnus et al., 2015) were generally comparable, although P_max observed had very low reliability. Area under the curve, O_max derived, and essential value showed the greatest reliability in the full sample (rs=0.75-0.77). These results provide evidence for the relative stability over time of demand and across AUD groups, particularly in those whose consumption remains stable.

Unique prediction of cannabis use severity and behaviors by delay discounting and behavioral economic demand

Few studies have simultaneously evaluated delay discounting and behavioral economic demand to determine their unique contribution to drug use. A recent study in cannabis users found that monetary delay discounting uniquely predicted cannabis dependence symptoms, whereas cannabis demand uniquely predicted use frequency. This study sought to replicate and extend this research by evaluating delay discounting and behavioral economic demand measures for multiple commodities and including a use quantity measure. Amazon.com's Mechanical Turk was used to sample individuals reporting recent cannabis use (n=64) and controls (n=72). Participants completed measures of monetary delay discounting as well as alcohol and cannabis delay discounting and demand. Cannabis users and controls did not differ on monetary delay discounting or alcohol delay discounting and demand. Among cannabis users, regression analyses indicated that cannabis delay discounting uniquely predicted use severity, whereas cannabis demand uniquely predicted use frequency and quantity. These effects remained significant after controlling for other delay discounting and demand measures. This research replicates previous outcomes relating delay discounting and demand with cannabis use and extends them by accounting for the contribution of multiple commodities. This research also demonstrates the ability of online crowdsourcing methods to complement traditional human laboratory techniques.

The effects of perceived quality on behavioral economic demand for marijuana: A web-based experiment

BACKGROUND

Given the growing legalization of recreational marijuana use and related increase in its prevalence in the United States, it is important to understand marijuana's appeal. We used a behavioral economic (BE) approach to examine whether the reinforcing properties of marijuana, including "demand" for marijuana, varied as a function of its perceived quality.

METHODS

Using an innovative, Web-based marijuana purchase task (MPT), a sample of 683 young-adult recreational marijuana users made hypothetical purchases of marijuana across three qualities (low, mid and high grade) at nine escalating prices per joint, ranging from $0/free to $20.

RESULTS

We used nonlinear mixed effects modeling to conduct demand curve analyses, which produced separate demand indices (e.g., P_max, elasticity) for each grade of marijuana. Consistent with previous research, as the price of marijuana increased, marijuana users reduced their purchasing. Demand also was sensitive to quality, with users willing to pay more for higher quality/grade marijuana. In regression analyses, demand indices accounted for significant variance in typical marijuana use.

CONCLUSIONS

This study illustrates the value of applying BE theory to young adult marijuana use. It extends past research by examining how perceived quality affects demand for marijuana and provides support for the validity of a Web-based MPT to examine the appeal of marijuana. Our results have implications for policies to regulate marijuana use, including taxation based on the quality of different marijuana products.

Comparing exponential and exponentiated models of drug demand in cocaine users

Drug purchase tasks provide rapid and efficient measurement of drug demand. Zero values (i.e., prices with zero consumption) present a quantitative challenge when using exponential demand models that exponentiated models may resolve. We aimed to replicate and advance the utility of using an exponentiated model by demonstrating construct validity (i.e., association with real-world drug use) and generalizability across drug commodities. Participants (N = 40 cocaine-using adults) completed Cocaine, Alcohol, and Cigarette Purchase Tasks evaluating hypothetical consumption across changes in price. Exponentiated and exponential models were fit to these data using different treatments of zero consumption values, including retaining zeros or replacing them with 0.1, 0.01, or 0.001. Excellent model fits were observed with the exponentiated model. Means and precision fluctuated with different replacement values when using the exponential model but were consistent for the exponentiated model. The exponentiated model provided the strongest correlation between derived demand intensity (Q0) and self-reported free consumption in all instances (Cocaine r = .88; Alcohol r = .97; Cigarette r = .91). Cocaine demand elasticity was positively correlated with alcohol and cigarette elasticity. Exponentiated parameters were associated with real-world drug use (e.g., weekly cocaine use) whereas these correlations were less consistent for exponential parameters. Our findings show that selection of zero replacement values affects demand parameters and their association with drug-use outcomes when using the exponential model but not the exponentiated model. This work supports the adoption of the exponentiated demand model by replicating improved fit and consistency and demonstrating construct validity and generalizability. (PsycINFO Database Record

The behavioral economics of young adult substance abuse

Alcohol and drug use peaks during young adulthood and can interfere with critical developmental tasks and set the stage for chronic substance misuse and associated social, educational, and health-related outcomes. There is a need for novel, theory-based approaches to guide substance abuse prevention efforts during this critical developmental period. This paper discusses the particular relevance of behavioral economic theory to young adult alcohol and drug misuse, and reviews of available literature on prevention and intervention strategies that are consistent with behavioral economic theory. Behavioral economic theory predicts that decisions to use drugs and alcohol are related to the relative availability and price of both alcohol and substance-free alternative activities, and the extent to which reinforcement from delayed substance-free outcomes is devalued relative to the immediate reinforcement associated with drugs. Behavioral economic measures of motivation for substance use are based on relative levels of behavioral and economic resource allocation towards drug versus alternatives, and have been shown to predict change in substance use over time. Policy and individual level prevention approaches that are consistent with behavioral economic theory are discussed, including brief interventions that increase future orientation and engagement in rewarding alternatives to substance use. Prevention approaches that increase engagement in constructive future-oriented activities among young adults (e.g., educational/vocational success) have the potential to reduce future health disparities associated with both substance abuse and poor educational/vocational outcomes.

Relative reinforcing efficacy of cigarettes as a predictor of smoking abstinence among treatment-seeking smokers

RATIONALE

Relative reinforcing efficacy (RRE) is a core feature of behavioral economic theories of addiction. A measure of RRE in smokers is the cigarette purchase task (CPT). Only one previous study has assessed whether CPT indices predict treatment outcomes among smokers with substance use disorders (SUDs) who were not motivated to quit smoking, limiting the generalizability of the results.

OBJECTIVES

This study was aimed at exploring demand indices as predictors of smoking abstinence among participants receiving a cognitive behavioral treatment (CBT) combined with contingency management (CM) versus CBT alone. It also sought to validate the CPT as a measure of RRE.

METHODS

Participants were 159 (62.3 % women) smokers aged 44.8 (SD 12.6) years randomized to CBT alone or combined with CM. They smoked an average of 21.1 (SD 8.5) cigarettes per day, and their mean score on the Fagerström Test for Nicotine Dependence (FTND) was 5.5 (SD 1.9). Demand indices were generated from a hypothetical CPT assessed at baseline.

RESULTS

Smoking levels were high (≥20 cigarettes) at prices of up to €0.10 per cigarette. Elasticity was the only index that predicted smoking abstinence at the end of treatment, but only in the CBT + CM condition. The variance explained by elasticity was 6.8 % in the independent model and 4.6 % in the covariate model. Cigarette demand indices and smoking-related measures were significantly associated.

CONCLUSION

This is the first research showing that CPT is a valid measure of CM outcome among treatment-seeking smokers. This study also provides evidence of convergent validity for the CPT.

Safety and tolerability of intranasal cocaine during phendimetrazine maintenance

RATIONALE

Phendimetrazine appears to have limited abuse potential and reduces cocaine self-administration in preclinical studies. No human studies have evaluated the safety and tolerability of cocaine in combination with phendimetrazine, which is a necessary next step in evaluating the efficacy of phendimetrazine for treating cocaine use disorder.

OBJECTIVES

This study determined the safety and tolerability of acute cocaine doses during chronic phendimetrazine treatment.

METHODS

Ten subjects completed this within-subject, placebo-controlled, inpatient study. Subjects were maintained on ascending oral phendimetrazine doses (0, 70, 140, and 210 mg/day). After at least seven maintenance days at each dose, subjects received ascending doses of intranasal cocaine (0, 10, 20, 40, and 80 mg), separated by 90 min, within one session.

RESULTS

Cocaine produced prototypical cardiovascular and subject-rated effects (e.g., increased blood pressure and ratings of like drug). The cardiovascular effects of cocaine alone were not clinically significant for an acute drug response (e.g., average heart rate did not approach tachycardia, 100 beats/min). Phendimetrazine enhanced peak heart rate following placebo and low cocaine doses, but these effects were also not clinically significant. Phendimetrazine was otherwise devoid of effects alone and did not alter the subject-rated effects of cocaine or hypothetical demand for cocaine on a purchase task.

CONCLUSIONS

Cocaine was safe and well tolerated during maintenance on a threefold range of phendimetrazine doses. Given this safety profile, the reduced abuse potential of phendimetrazine and promising preclinical research, future human laboratory studies, and possibly clinical trials should evaluate the efficacy of phendimetrazine for reducing cocaine use.

The Computational Complexity of Valuation and Motivational Forces in Decision-Making Processes

The concept of value is fundamental to most theories of motivation and decision making. However, value has to be measured experimentally. Different methods of measuring value produce incompatible valuation hierarchies. Taking the agent's perspective (rather than the experimenter's), we interpret the different valuation measurement methods as accessing different decision-making systems and show how these different systems depend on different information processing algorithms. This identifies the translation from these multiple decision-making systems into a single action taken by a given agent as one of the most important open questions in decision making today. We conclude by looking at how these different valuation measures accessing different decision-making systems can be used to understand and treat decision dysfunction such as in addiction.

Identification and management of nonsystematic purchase task data: Toward best practice

Experimental assessments of demand allow the examination of economic phenomena relevant to the etiology, maintenance, and treatment of addiction and other pathologies (e.g., obesity). Although such assessments have historically been resource intensive, development and use of purchase tasks-in which participants purchase 1 or more hypothetical or real commodities across a range of prices-have made data collection more practical and have increased the rate of scientific discovery. However, extraneous sources of variability occasionally produce nonsystematic demand data, in which price exerts either no or inconsistent effects on the purchases of individual participants. Such data increase measurement error, can often not be interpreted in light of research aims, and likely obscure effects of the variable(s) under investigation. Using data from 494 participants, we introduce and evaluate an algorithm (derived from prior methods) for identifying nonsystematic demand data, wherein individual participants' demand functions are judged against 2 general, empirically based assumptions: (a) global, price-dependent reduction in consumption and (b) consistency in purchasing across prices. We also introduce guidelines for handling nonsystematic data, noting some conditions in which excluding such data from primary analyses may be appropriate and others in which doing so may bias conclusions. Adoption of the methods presented here may serve to unify the research literature and facilitate discovery.

Contingency Management and Deliberative Decision-Making Processes

Contingency management is an effective treatment for drug addiction. The current explanation for its success is rooted in alternative reinforcement theory. We suggest that alternative reinforcement theory is inadequate to explain the success of contingency management and produce a model based on demand curves that show how little the monetary rewards offered in this treatment would affect drug use. Instead, we offer an explanation of its success based on the concept that it accesses deliberative decision-making processes. We suggest that contingency management is effective because it offers a concrete and immediate alternative to using drugs, which engages deliberative processes, improves the ability of those deliberative processes to attend to non-drug options, and offsets more automatic action-selection systems. This theory makes explicit predictions that can be tested, suggests which users will be most helped by contingency management, and suggests improvements in its implementation.

Economic demand predicts addiction-like behavior and therapeutic efficacy of oxytocin in the rat

Development of new treatments for drug addiction will depend on high-throughput screening in animal models. However, an addiction biomarker fit for rapid testing, and useful in both humans and animals, is not currently available. Economic models are promising candidates. They offer a structured quantitative approach to modeling behavior that is mathematically identical across species, and accruing evidence indicates economic-based descriptors of human behavior may be particularly useful biomarkers of addiction severity. However, economic demand has not yet been established as a biomarker of addiction-like behavior in animals, an essential final step in linking animal and human studies of addiction through economic models. We recently developed a mathematical approach for rapidly modeling economic demand in rats trained to self-administer cocaine. We show here that economic demand, as both a spontaneous trait and induced state, predicts addiction-like behavior, including relapse propensity, drug seeking in abstinence, and compulsive (punished) drug taking. These findings confirm economic demand as a biomarker of addiction-like behavior in rats. They also support the view that excessive motivation plays an important role in addiction while extending the idea that drug dependence represents a shift from initially recreational to compulsive drug use. Finally, we found that economic demand for cocaine predicted the efficacy of a promising pharmacotherapy (oxytocin) in attenuating cocaine-seeking behaviors across individuals, demonstrating that economic measures may be used to rapidly identify the clinical utility of prospective addiction treatments.

Elevated alcohol demand is associated with driving after drinking among college student binge drinkers

BACKGROUND

Alcohol-impaired driving among college students represents a significant public health concern, yet little is known about specific theoretical and individual difference risk factors for driving after drinking among heavy drinking college students. This study evaluated the hypothesis that heavy drinkers with elevated alcohol demand would be more likely to report drinking and driving.

METHOD

Participants were 207 college students who reported at least 1 heavy drinking episode (4/5 or more drinks in 1 occasion for a woman/man) in the past month. Participants completed an alcohol purchase task that assessed hypothetical alcohol consumption across 17 drink prices and an item from the Young Adult Alcohol Consequences Questionnaire that assessed driving after drinking.

RESULTS

In binary logistic regression models that controlled for drinking level, gender, ethnicity, age, and sensation seeking, participants who reported higher demand were more likely to report driving after drinking.

CONCLUSIONS

These results provide support for behavioral economics models of substance abuse that view elevated/inelastic demand as a key etiological feature of substance misuse.

Behavioral economic measures of alcohol reward value as problem severity indicators in college students

The aims of the current study were to examine the associations among behavioral economic measures of alcohol value derived from 3 distinct measurement approaches, and to evaluate their respective relations with traditional indicators of alcohol problem severity in college drinkers. Five behavioral economic metrics were derived from hypothetical demand curves that quantify reward value by plotting consumption and expenditures as a function of price, another metric measured proportional behavioral allocation and enjoyment related to alcohol versus other activities, and a final metric measured relative discretionary expenditures on alcohol (RDEA). The sample included 207 heavy-drinking college students (53% female) who were recruited through an on-campus health center or university courses. Factor analysis revealed that the alcohol valuation construct comprises 2 factors: 1 factor that reflects participants' levels of alcohol price sensitivity (demand persistence), and a second factor that reflects participants' maximum consumption and monetary and behavioral allocation toward alcohol (amplitude of demand). The demand persistence and behavioral allocation metrics demonstrated the strongest and most consistent multivariate relations with alcohol-related problems, even when controlling for other well-established predictors. The results suggest that behavioral economic indices of reward value show meaningful relations with alcohol problem severity in young adults. Despite the presence of some gender differences, these measures appear to be useful problem indicators for men and women.