Behavioral economics: a novel experimental approach to the study of drug dependence

Biological sex modulates the efficacy of 2,5-dimethoxy-4-iodoamphetamine (DOI) to mitigate fentanyl demand

BACKGROUND

Overdose deaths remain high for opioid use disorder, emphasizing the need to pursue innovative therapeutics. Classic psychedelic drugs that engage many monoamine receptors mitigate opioid use. Here, we tested the hypothesis that the preferential serotonin 5-HT2AR agonist, 2,5-dimethoxy-4-iodoamphetamine (DOI) could reduce the demand for fentanyl in a preclinical model of fentanyl self-administration.

METHODS

Male and female Sprague-Dawley rats (n = 25-29) were implanted with indwelling jugular catheters and allowed to self-administer fentanyl (3.2μg/kg/infusion). Rats progressed to a novel low price twice within-session threshold procedure where rats sampled the lowest price twice before decreasing the dose of fentanyl by a ¼ log every 10minutes across 11 doses. Once stable, rats were pretreated with saline or DOI (0.01, 0.03, 1mg/kg). Fentanyl consumption was analyzed using an exponentiated demand function to extract the dependent variables, Q0 and α.

RESULTS

Male and female rats acquired fentanyl self-administration in the lowest price twice within-session threshold procedure. DOI dose-dependently altered fentanyl intake such that 5-HT2AR activation decreased Q0 in female rats but increased Q0 in male rats. For demand elasticity, DOI increased α in male rats but did not alter α in female rats. DOI did not alter inactive lever presses or latency.

CONCLUSION

DOI reduces consumption at minimally constrained costs but did not affect the reinforcement value of fentanyl in female rats. Alternatively, DOI significantly reduced the reinforcement value of fentanyl in male rats. Biological sex alters the therapeutic efficacy of DOI and 5-HT2AR activation sex-dependently alters opioid reinforcement.

The day-level effects of recovery community center attendance on indicators of recovery wellbeing and risk

BACKGROUND

Recovery community centers (RCCs) are a relatively new resource in the recovery support landscape aimed at building their members' recovery capital. In recent years, interest in the value of RCCs has grown, however, no studies have used within-person methods to consider how RCCs may impact the day-to-day lives of their attendees. Using within-person data drawn from members of RCCs, this study examined how visiting RCCs was associated with several same-day indicators of recovery wellbeing and risk: daily sense of meaningfulness, recovery identity, negative affect, and positive affect.

METHODS

Participants were 94 visitors of six RCCs in western Pennsylvania. Daily diary methods collected 10 nightly reports of daily RCC attendance and end-of-day meaningfulness, recovery identity, negative affect, and positive affect. Multilevel modeling accounted for nesting in the intensive longitudinal data. In independent models, the study regressed meaningfulness, recovery identity, negative affect, and positive affect onto day- and person-level RCC attendance.

RESULTS

Within-person associations between RCC attendance and meaningfulness (b = 6.96, SE = 1.66, p < .001), recovery identity (b = 4.75, SE = 1.08, p < .001), and PA (b = 3.82, SE = 1.45, p < .01) were significant, although NA was not (b = -2.41, SE = 1.34, n.s.). All day- by person-level RCC attendance interactions (in preliminary models) and between-person associations were non-significant across recovery outcomes.

CONCLUSIONS

The results indicated that on days participants visited RCCs, they reported significantly higher levels of meaningfulness, recovery identity, and positive affect, although negative affect levels did not significantly differ. Also, those who attended RCCs more frequently did not generally report different levels of recovery wellbeing and risk. Taken together, results suggest visiting RCCs works on a daily basis to support interpersonal processes related to positive recovery outcomes. That RCC visits do not appear to reduce negative affect suggests that additional programs may be needed to address negative affect. The within-person design provided insight into the dynamic processes that contribute to the intrapersonal states that support recovery and a practical approach to examining whether and how RCCs might support recovery. By using individuals as their own controls, the study design provided strong counterfactual inference.

Outdoor Medical Cannabis Advertising in Oklahoma: Examining Regulatory Compliance and Social Meanings in Billboard Content

Background: Medical cannabis currently dominates the U.S. cannabis advertising landscape. The public is increasingly exposed to outdoor cannabis advertising, which increases positive attitudes about and intentions to use cannabis. Research is lacking regarding outdoor cannabis advertising content. This article characterizes the content of outdoor cannabis advertising in Oklahoma, one of the fastest growing U.S. medical cannabis markets. Methods: We conducted a content analysis of cannabis advertising billboard images (n = 73) from Oklahoma City and Tulsa, photographed May 2019-November 2020. We followed a primarily inductive, iterative team approach to thematically analyze billboard content in NVIVO. We reviewed all images, identified a broad coding taxonomy, and then incorporated emergent codes and those related to advertising regulation (e.g. youth/children). We totaled frequencies of code application across billboards and reexamined billboards for final themes. Results: Major themes were social meanings related to cannabis subculture, formal medical systems, and nature, and the presence of company contact information. Minor themes related to convenience, price promotions, store proximity, U.S. affiliation, product quality, and spirituality. State advertising regulation violations were rare, with the exception of content that may promote curative or therapeutic effects (4%) and misrepresentation of product state of origin (1.4%). Conclusion: Outdoor medical cannabis advertising in Oklahoma blurs boundaries between formal medical discourses and cannabis subculture that is suspicious of messaging from authorities and regards cannabis as harmless and natural. Increased monitoring of advertising regulation compliance and greater understanding of social discourses within emerging markets is needed to promote public health within the context of cannabis advertising.

Behavioral economics indices predict alcohol use and consequences in young men at 4-year follow-up

BACKGROUND AND AIMS

The alcohol purchase task (APT), which presents a scenario and asks participants how many drinks they would purchase and consume at different prices, generates indices of alcohol reward value that have shown robust associations with alcohol-related outcomes in numerous studies. The aim was to test its prospective validity at 4-year follow-up.

DESIGN

Prospective cohort study.

SETTING

General population sample of young Swiss men.

PARTICIPANTS

A total of 4594 Swiss young men (median age = 21, 25th - 75th quartiles = 20.5 - 21.5) completed baseline questionnaires; among those, 4214 (91.7%) were successfully followed-up 4 years later.

MEASUREMENTS

Alcohol reward value parameters (i.e. intensity, the planned consumption when drinks are free; breakpoint, the price at which consumption would be suppressed; O_max , the maximum alcohol expenditure; P_max , the price associated with O_max ; and elasticity, the relative change in alcohol consumption as a function of the relative change in price) were derived from the APT at baseline and used to predict self-reported weekly drinking amount, monthly binge drinking, alcohol-related consequences and DSM-5 alcohol use disorder criteria.

FINDINGS

Regression analyses, adjusting for the baseline alcohol measure, age, linguistic region and socio-economic indicators showed that intensity, breakpoint, O_max and elasticity significantly predicted all tested outcomes in the expected direction (e.g. standardized incidence rate ratio [95% confidence interval] = 1.11 [1.07-1.15], 1.07 [1.03-1.10], 1.08 [1.04-1.11], and 0.92 [0.89-0.95], respectively, for weekly drinking amount, all P < 0.001). P_max did not significantly predict any outcomes. Non-adjusted correlations, baseline adjusted regression and ancillary analyses using (1) latent alcohol variables, (2) multiple imputation for missing data and (3) replications in training and testing subsamples to evaluate predictive accuracy provided consistent findings.

CONCLUSIONS

The alcohol purchase task demand curve measures of alcohol reward value are useful in characterizing alcohol-related risk in young men and have long-term predictive utility.

Decreased excitability of leptin-sensitive anterior insula pyramidal neurons in a rat model of compulsive food demand

Compulsive eating is an overlapping construct with binge eating that shares many characteristics with substance use disorders. Compulsive eating may impact millions of Americans; presenting in some cases of binge eating disorders, overweight/obesity, and among individuals who have not yet been diagnosed with a recognized eating disorder. To study the behavioral and neurobiological underpinnings of compulsive eating, we employ a published rodent model using cyclic intermittent access to a palatable diet to develop a self-imposed binge-withdrawal cycle. Here, we further validated this model of compulsive eating in female Wistar rats, through the lens of behavioral economic analyses and observed heightened demand intensity, inelasticity and essential value as well as increased food-seeking during extinction. Using electrophysiological recordings in the anterior insular cortex, a region previously implicated in modulating compulsive-like eating in intermittent access models, we observed functional adaptations of pyramidal neurons. Within the same neurons, application of leptin led to further functional adaptations, suggesting a previously understudied, extrahypothalamic role of leptin in modulating feeding-related cortical circuits. Collectively, the findings suggest that leptin may modulate food-related motivation or decision-making via a plastic cortical circuit that is influenced by intermittent access to a preferred diet. These findings warrant further study of whether behavioral economics analysis of compulsive eating can impact disordered eating outcomes in humans and of the translational relevance of a leptin-sensitive anterior insular circuit implicated in these behaviors.

The Influence of Episodic Future Thinking and Graphic Warning Labels on Delay Discounting and Cigarette Demand

Delay discounting and operant demand are two behavioral economic constructs that tend to covary, by degree, with cigarette smoking status. Given historically robust associations between adverse health outcomes of smoking, a strong preference for immediate reinforcement (measured with delay discounting), and excessive motivation to smoke cigarettes (measured with operant demand), researchers have made numerous attempts to attenuate the extent to which behaviors corresponding to these constructs acutely appear in smokers. One approach is episodic future thinking, which can reportedly increase the impact of future events on present decision making as well as reduce the reinforcing value of cigarettes. Graphic cigarette pack warning labels may also reduce smoking by increased future orientation. Experiment 1 evaluated the combined effects of episodic future thinking and graphic warning labels on delay discounting; Experiment 2 evaluated solely the effects of episodic future thinking on delay discounting and operant demand. We observed no statistically significant effects of episodic future thinking when combined with graphic warning labels or when assessed on its own. These results serve as a call for further research on the boundary conditions of experimental techniques reported to alter behaviors associated with cigarette smoking.

The importance of psychology for shaping legal cannabis regulation

Different patterns of cannabis use can be traced directly back to different interactions between 2 types of variables: pharmacological and environmental. As legal cannabis expands in the U.S. and around the world, state and national regulatory agencies are gaining control over these variables. Specifically, regulatory agencies are increasingly capable of altering (a) the pharmacological properties of cannabis products and (b) the way these products are distributed to the population. Consequently, cannabis regulatory agencies are in a unique position to use evidence from psychological science to alter cannabis consumption patterns in ways that mitigate potential harm to public health. However, most state-level legal cannabis regulatory systems in the U.S. are not yet evidence-based or public health-oriented. This applied review and commentary draws on evidence from the psychological science literature to help regulators better understand the types of behaviors they must address and guide empirically supported regulation of THC-laden cannabis, whether used putatively for medical or recreational reasons. This review is organized into 3 parts that correspond to the 3 primary agents within the cannabis regulation ecosystem: (a) the cannabis consumer, (b) the cannabis industry, and (c) the cannabis regulatory agency. Within this structure, the review addresses critical psychological variables that drive cannabis consumer and industry behaviors and discusses how regulatory agencies can use this information to protect public health. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Behavioral economic measurement of cigarette demand: A descriptive review of published approaches to the cigarette purchase task

The cigarette purchase task (CPT) is a behavioral economic method for assessing demand for cigarettes. Growing interest in behavioral correlates of tobacco use in clinical and general populations as well as empirical efforts to inform policy has seen an increase in published articles employing the CPT. Accordingly, an examination of the published methods and procedures for obtaining these behavioral economic metrics is timely. The purpose of this investigation was to provide a review of published approaches to using the CPT. We searched specific Boolean operators (["behavioral economic" AND "purchase task"] OR ["demand" AND "cigarette"]) and identified 49 empirical articles published through the year 2018 that reported administering a CPT. Articles were coded for participant characteristics (e.g., sample size, population type, age), CPT task structure (e.g., price framing, number and sequence of prices; vignettes, contextual factors), and data analytic approach (e.g., method of generating indices of cigarette demand). Results of this review indicate no standard approach to administering the CPT and underscore the need for replicability of these behavioral economic measures for the purpose of guiding clinical and policy decisions. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Understanding Addiction Using Animal Models

Drug addiction is a neuropsychiatric disorder with grave personal consequences that has an extraordinary global economic impact. Despite decades of research, the options available to treat addiction are often ineffective because our rudimentary understanding of drug-induced pathology in brain circuits and synaptic physiology inhibits the rational design of successful therapies. This understanding will arise first from animal models of addiction where experimentation at the level of circuits and molecular biology is possible. We will review the most common preclinical models of addictive behavior and discuss the advantages and disadvantages of each. This includes non-contingent models in which animals are passively exposed to rewarding substances, as well as widely used contingent models such as drug self-administration and relapse. For the latter, we elaborate on the different ways of mimicking craving and relapse, which include using acute stress, drug administration or exposure to cues and contexts previously paired with drug self-administration. We further describe paradigms where drug-taking is challenged by alternative rewards, such as appetitive foods or social interaction. In an attempt to better model the individual vulnerability to drug abuse that characterizes human addiction, the field has also established preclinical paradigms in which drug-induced behaviors are ranked by various criteria of drug use in the presence of negative consequences. Separation of more vulnerable animals according to these criteria, along with other innate predispositions including goal- or sign-tracking, sensation-seeking behavior or impulsivity, has established individual genetic susceptibilities to developing drug addiction and relapse vulnerability. We further examine current models of behavioral addictions such as gambling, a disorder included in the DSM-5, and exercise, mentioned in the DSM-5 but not included yet due to insufficient peer-reviewed evidence. Finally, after reviewing the face validity of the aforementioned models, we consider the most common standardized tests used by pharmaceutical companies to assess the addictive potential of a drug during clinical trials.

Sensitivity of hypothetical purchase task indices when studying substance use: A systematic literature review

Hypothetical Purchase Tasks (HPTs) simulate demand for a substance as a function of escalating price. HPTs are increasingly used to examine relationships between substance-related correlates and outcomes and demand typically characterized using a common battery of indices (Intensity, Omax, Pmax, Breakpoint, Elasticity). This review examines the relative sensitivity of the HPT indices. Reports were identified using the search term "purchase task" in PubMed and Web of Science. For inclusion, reports had to be original studies in English, examine relationships between HPT indices and substance-related correlates or outcomes, and appear in a peer-reviewed journal through December 2017. Indices were compared using effect sizes (Cohen's d) and the proportion of studies in which statistically significant relationships were observed. The search identified 1274 reports with 114 (9%) receiving full-text review and 82 (6%) meeting inclusion criteria. 41 reports examined alcohol, 34 examined cigarettes/nicotine products, and 10 examined other substances. Overall, statistically significant relationships between HPT indices and substance-related correlates and outcomes were most often reported for Intensity (88.61%, 70/79), followed by Omax (81.16%, 56/69), Elasticity (72.15%, 57/59), Breakpoint (62.12%, 41/66), and Pmax (48.08%; 25/52). The largest effect sizes were observed for Intensity (0.75 ± 0.04, CI 0.67-0.84) and Omax (0.64 ± 0.04, CI 0.56-0.71), followed by Elasticity (0.44 ± 0.04, CI 0.37-0.51), Breakpoint (0.30 ± 0.03, CI 0.25-0.36), and Pmax (0.25 ± 0.04, CI 0.18-0.33). Patterns were largely consistent across substances. In conclusion, HPTs can be highly effective in revealing relationships between demand and substance-related correlates and outcomes, with Intensity and Omax exhibiting the greatest sensitivity.

An Evaluation of Operant Behavioural Economics in Functional Communication Training for Severe Problem Behaviour

Objective: This single-case experiment examined the use of behavioural economic concepts in a function-based treatment for problem behaviour. Methods: Behavioural economic analyses were used to evaluate the strength of functions of problem behaviour and this information was used to inform elements of function-based treatment for one child with a neurodevelopmental disorder. Results: Findings from this experiment indicated that the incorporation of behavioural economic measures resulted in positive treatment effects that were maintained throughout all phases of the evaluation, including those implemented by caregivers. Conclusions: These results suggest that behavioural economic concepts and procedures can be successful adjuncts to evidence-based assessments and treatments for problem behaviour.

The role of orexin-1 receptor signaling in demand for the opioid fentanyl

The orexin system is a potential treatment target for drug addiction. Orexin-1 receptor (OxR1) antagonism reduces demand for cocaine and remifentanil, indicating that orexin-based therapies may reduce demand for many classes of abused drugs. However, pharmacokinetics vary greatly among opioids and it is unclear if OxR1 antagonism would reduce demand for all opioids, particularly ones with high abuse liability. Here, we established a behavioral economics (BE) procedure to assess the effects of OxR1 antagonism on demand for the highly abused opioid fentanyl. We also investigated the utility of our procedure to predict OxR1 antagonism efficacy and relapse propensity. Demand parameters α (demand elasticity or price sensitivity of consumption, an inverse measure of drug motivation) and Q_o (drug consumption at null cost) were assessed. The OxR1 antagonist SB-334867 (SB) decreased motivation (increased α) for fentanyl without affecting Q_o. Baseline α values predicted SB efficacy, such that SB was most effective at reducing motivation (increasing α) in highly motivated rats. Baseline α values predicted the amount of cued reinstatement of fentanyl seeking; this reinstatement behavior was attenuated by SB administration. These results highlight the promise of the orexin system as a treatment target for opioid addiction and emphasize the usefulness of BE procedures in the study of opioid abuse.

A Biopsychosocial Overview of the Opioid Crisis: Considering Nutrition and Gastrointestinal Health

The opioid crisis has reached epidemic proportions in the United States with rising overdose death rates. Identifying the underlying factors that contribute to addiction vulnerability may lead to more effective prevention strategies. Supply side environmental factors are a major contributing component. Psychosocial factors such as stress, trauma, and adverse childhood experiences have been linked to emotional pain leading to self-medication. Genetic and epigenetic factors associated with brain reward pathways and impulsivity are known predictors of addiction vulnerability. This review attempts to present a biopsychosocial approach that connects various social and biological theories related to the addiction crisis. The emerging role of nutrition therapy with an emphasis on gastrointestinal health in the treatment of opioid use disorder is presented. The biopsychosocial model integrates concepts from several disciplines, emphasizing multicausality rather than a reductionist approach. Potential solutions at multiple levels are presented, considering individual as well as population health. This single cohesive framework is based on the interdependency of the entire system, identifying risk and protective factors that may influence substance-seeking behavior. Nutrition should be included as one facet of a multidisciplinary approach toward improved recovery outcomes. Cross-disciplinary collaborative efforts, new ideas, and fiscal resources will be critical to address the epidemic.

The R package beezdemand: Behavioral Economic Easy Demand

beezdemand: Behavioral Economic Easy Demand, a novel package for performing behavioral economic analyses, is introduced and evaluated. beezdemand extends the statistical program to facilitate many of the analyses performed in studies of behavioral economic demand. The package supports commonly used options for modeling operant demand and performs data screening, fits models of demand, and calculates numerous measures relevant to applied behavioral economists. The free and open source beezdemand package is compared to commercially available software (i.e., GraphPad Prism™) using peer-reviewed and simulated data. The results of this study indicated that beezdemand provides results consistent with commonly used commercial software but provides a wider range of methods and functionality desirable to behavioral economic researchers. A brief overview of the package is presented, its functionality is demonstrated, and considerations for its use are discussed.

What Is Addiction? How Can Animal and Human Research Be Used to Advance Research, Diagnosis, and Treatment of Alcohol and Other Substance Use Disorders?

The current article highlights key issues in defining, studying, and treating addiction, a concept related to but distinct from substance use disorders. The discussion is based upon a roundtable discussion at the 2017 annual meeting of the Research Society on Alcoholism where Warren K. Bickel and John C. Crabbe were charged with answering a range of questions posed by Kenneth J. Sher. All the presenters highlighted a number of central concerns for those interested in assessing and treating addiction as well as those seeking to conduct basic preclinical research that is amenable to meaningful translation to the human condition. In addition, the discussion illustrated both the power and limitations of using any single theory to explain multiple phenomena subsumed under the rubric of addiction. Among the major issues examined were the important differences between traditional diagnostic approaches and current concepts of addiction, the difficulty of modeling key aspects of human addiction in nonhuman animals, key aspects of addiction that have, to date, received little empirical attention, and the importance of thinking of recovery as a phenomenon that possibly involves processes distinct from those undergirding the development and maintenance of addiction.

Environmental enrichment and drug value: a behavioral economic analysis in male rats

Rats raised in an enriched condition (EC) show decreased stimulant self-administration relative to rats reared in an isolated condition (IC). However, few studies have examined the behavioral mechanisms underlying this environment-induced difference in self-administration. Because economic demand for drugs of abuse predicts addiction-like behavior in both humans and animals, we applied a behavioral economic analysis to cocaine self-administration data in EC and IC rats. During cocaine self-administration, the dose decreased across blocks of trials (0.75-0.003 mg/kg/inf), which allowed for a determination of demand intensity and demand elasticity. Demand intensity did not differ between EC and IC rats; however, cocaine was more elastic in EC rats relative to IC rats (i.e. EC rats were less willing to respond for cocaine as the unit price increased). When EC rats were placed in an isolated condition, demand elasticity decreased, whereas elasticity increased for IC rats placed in an enriched condition. Additionally, we applied behavioral economic analyses to previously published self-administration data and found that our results replicate past findings with cocaine and methylphenidate. To determine if differences in demand elasticity are specific to drug reinforcement, a separate group of rats was tested in sucrose or saccharin self-administration. Results showed that sucrose and saccharin were more elastic in EC rats relative to IC rats, and demand intensity was lower for saccharin in EC rats relative to IC rats. Overall, drug and nondrug reinforcers are more elastic in EC rats, which may account for the protective effects of environmental enrichment against stimulant self-administration.

Fentanyl: Receptor pharmacology, abuse potential, and implications for treatment

Opioid overdoses, many of which are attributed to use of illicit fentanyl, are currently one of the leading causes of death in the U.S. Although fentanyl has been used safely for decades in clinical settings, the widespread use of illicit fentanyl is a recent phenomenon. Starting in 2013, illicitly manufactured fentanyl and its analogs began to appear on the streets. These substances were added to or sold as heroin, often unbeknownst to the user. Because fentanyl is so potent, only small amounts are needed to produce pharmacological effects, but the margin between safe and toxic doses is narrow. Surprisingly little is known about the exact signaling mechanisms underlying fentanyl-related respiratory depression or the effectiveness of naloxone in reversing this effect. Similarly, little is known about the ability of treatment medications such as buprenorphine, methadone, or naltrexone to reduce illicit fentanyl use. The present article reviews the receptor, preclinical and clinical pharmacology of fentanyl, and how its pharmacology may predict the effectiveness of currently approved medications for treating illicit fentanyl use.

Behavioral Economic Research in Addiction as an Area of Growth for the Experimental Analysis of Behavior

Behavioral economics, a synthesis of the experimental analysis of behavior (EAB) and economics, seeks to determine the relative value of reinforcers as a function of various environmental constraints. Early animal and human studies often focused on drug reinforcement, and this has continued to the present. In particular, behavioral economic analyses of human and animal behavior in relation to nicotine and cigarette smoking have contributed to a greater understanding of this behavior, and to a greater reliance on these methods in the field of smoking cessation treatment, tobacco regulatory science and tobacco control. In this commentary, we briefly describe the history of behavioral economics in the context of EAB methods, the particular contribution of these methods to understanding cigarette smoking and the advance of tobacco regulation, as well as opportunities for growth and remaining challenges in this area. As behavioral economics continues to stimulate research and inform policy, we propose that the underlying elements of a rigorous analytic approach to understanding behavior are key contributors to the fruitfulness of this approach.

The Demand Curve Analyzer: Behavioral economic software for applied research

Free and open-source software for applying models of operant demand called the Demand Curve Analyzer (DCA) was developed and systematically evaluated for use in research. The software was constructed to streamline the use of recommended screening measures, prepare suitable scaling parameters, fit one of several models of operant demand, and provide publication-quality figures. The DCA allows users to easily import price and consumption data into spreadsheet-based controls and to perform statistical modeling with the aid of a graphical user interface. The results from computer simulations and reanalyses of published study data indicated that the DCA provides results consistent with commercially available software that has been traditionally used to apply these analyses (i.e., GraphPadTM Prism). Further, the DCA provides additional functionality that other statistical packages do not include. Practical issues and future directions related to the determination of scaling parameter k, screening for nonsystematic data, and the incorporation of more advanced behavioral economic methods are also discussed.

Does preference rank predict substitution for the reinforcer for problem behavior? a behavioral economic analysis

Predictions made under low response requirements inherent in most preference assessments (PAs) do not guarantee the utility of stimuli in treatments. We examined whether PA rank would predict how well stimuli supported compliance for children with escape-maintained problem behavior by examining the relation between PA rank and demand elasticity across five fixed-ratio values. Three patterns were observed: All stimuli were selected equally across values, higher ranked stimuli were selected more at higher values, and something other than the highest ranked stimulus was selected more at higher values (i.e., mixed correspondence).

Escalated cocaine "binges" in rats: enduring effects of social defeat stress or intra-VTA CRF

RATIONALE

Exposure to intermittent social defeat stress elicits corticotropin releasing factor (CRF) release into the VTA and induces long-term modulation of mesocorticolimbic dopamine activity in rats. These adaptations are associated with an intense cocaine-taking phenotype, which is prevented by CRF receptor antagonists.

OBJECTIVE

The present studies examine whether infusion of CRF into the VTA is sufficient to escalate cocaine-taking behavior, in the absence of social defeat experience. Additionally, we aimed to characterize changes in cocaine valuation that may promote binge-like cocaine intake.

METHODS

Male Long-Evans rats were microinjected into the VTA with CRF (50 or 500 ng/side), vehicle, or subjected to social defeat stress, intermittently over 10 days. Animals were then trained to self-administer IV cocaine (FR5). Economic demand for cocaine was evaluated using a within-session behavioral-economics threshold procedure, which was followed by a 24-h extended access "binge."

RESULTS

Rats that experienced social defeat or received intra-VTA CRF microinfusions (50 ng) both took significantly more cocaine than controls over the 24-h binge but showed distinct patterns of intake. Behavioral economic analysis revealed that individual demand for cocaine strongly predicts binge-like consumption, and demand elasticity (i.e. α) is augmented by intra-VTA CRF, but not by social defeat. The effects of CRF on cocaine-taking were also prevented by intra-VTA pretreatment with CP376395, but not Astressin-2B.

CONCLUSIONS

Repeated infusion of CRF into the VTA persistently alters cocaine valuation and intensifies binge-like drug intake in a CRF-R1-dependent manner. Conversely, the persistent pattern of cocaine bingeing induced by social defeat stress may suggest impaired inhibitory control, independent of reward valuation.

Longitudinal and reciprocal relations between delay discounting and crime

Theorists argue that self-control failure is the underlying cause of criminal behavior, with previous research linking poor self-control to delinquency and drug use. The path from self-control to crime is well-established, but less is known about whether criminal behavior contributes to self-control deficits over time. We investigated bi-directional relations between self-control assessed via a delay discounting task and self-reported crime over a three-year period. During their first, second (73.38% retention rate), and third (63.12% retention rate) years of college, 526 undergraduates completed a delay discounting task and reported on their criminal behavior. In order to maximize variability, participants with conduct problems were overrecruited, comprising 23.1% of the final sample. As expected, more discounting of hypothetical monetary rewards significantly predicted future property crime across a one and two-year period, even when controlling for initial levels of both. This study also demonstrated evidence of a bi-directional relationship; violent crime predicted higher rates of delay discounting one year later. These results suggest that bi-directional relations exist between self-control and types of crime.

Disrupted white matter structural connectivity in heroin abusers

Neurocognitive impairment is one of the factors that put heroin abusers at greater risk for relapse, and deficits in related functional brain connections have been found. However, the alterations in structural brain connections that may underlie these functional and neurocognitive impairments remain largely unknown. In the present study, we investigated topological organization alterations in the structural network of white matter in heroin abusers and examined the relationships between the network changes and clinical measures. We acquired diffusion tensor imaging datasets from 76 heroin abusers and 78 healthy controls. Network-based statistic was applied to identify alterations in interregional white matter connectivity, and graph theory methods were used to analyze the properties of global networks. The participants also completed a battery of neurocognitive measures. One increased subnetwork characterizing widespread abnormalities in structural connectivity was present in heroin users, which mainly composed of default-mode, attentional and visual systems. The connection strength was positively correlated with increases in fractional anisotropy in heroin abusers. Intriguingly, the changes in within-frontal and within-temporal connections in heroin abusers were significantly correlated with daily heroin dosage and impulsivity scores, respectively. These findings suggest that heroin abusers have extensive abnormal white matter connectivity, which may mediate the relationship between heroin dependence and clinical measures. The increase in white matter connectivity may be attributable to the inefficient microstructure integrity of white matter. The present findings extend our understanding of cerebral structural disruptions that underlie neurocognitive and functional deficits in heroin addiction and provide circuit-level markers for this chronic disorder.

Some current dimensions of the behavioral economics of health-related behavior change

Health-related behaviors such as tobacco, alcohol and other substance use, poor diet and physical inactivity, and risky sexual practices are important targets for research and intervention. Health-related behaviors are especially pertinent targets in the United States, which lags behind most other developed nations on common markers of population health. In this essay we examine the application of behavioral economics, a scientific discipline that represents the intersection of economics and psychology, to the study and promotion of health-related behavior change. More specifically, we review what we consider to be some core dimensions of this discipline when applied to the study health-related behavior change. Behavioral economics (1) provides novel conceptual systems to inform scientific understanding of health behaviors, (2) translates scientific understanding into practical and effective behavior-change interventions, (3) leverages varied aspects of behavior change beyond increases or decreases in frequency, (4) recognizes and exploits trans-disease processes and interventions, and (5) leverages technology in efforts to maximize efficacy, cost effectiveness, and reach. These dimensions are overviewed and their implications for the future of the field discussed.

Toward quantifying the abuse liability of ultraviolet tanning: A behavioral economic approach to tanning addiction

Many adults engage in ultraviolet indoor tanning despite evidence of its association with skin cancer. The constellation of behaviors associated with ultraviolet indoor tanning is analogous to that in other behavioral addictions. Despite a growing literature on ultraviolet indoor tanning as an addiction, there remains no consensus on how to identify ultraviolet indoor tanning addictive tendencies. The purpose of the present study was to translate a behavioral economic task more commonly used in substance abuse to quantify the "abuse liability" of ultraviolet indoor tanning, establish construct validity, and determine convergent validity with the most commonly used diagnostic tools for ultraviolet indoor tanning addiction (i.e., mCAGE and mDSM-IV-TR). We conducted a between-groups study using a novel hypothetical Tanning Purchase Task to quantify intensity and elasticity of ultraviolet indoor tanning demand and permit statistical comparisons with the mCAGE and mDSM-IV-TR. Results suggest that behavioral economic demand is related to ultraviolet indoor tanning addiction status and adequately discriminates between potential addicted individuals from nonaddicted individuals. Moreover, we provide evidence that the Tanning Purchase Task renders behavioral economic indicators that are relevant to public health research. The present findings are limited to two ultraviolet indoor tanning addiction tools and a relatively small sample of high-risk ultraviolet indoor tanning users; however, these pilot data demonstrate the potential for behavioral economic assessment tools as diagnostic and research aids in ultraviolet indoor tanning addiction studies.

Validity of the alcohol purchase task: a meta-analysis

BACKGROUND AND AIMS

Behavioral economists assess alcohol consumption as a function of unit price. This method allows construction of demand curves and demand indices, which are thought to provide precise numerical estimates of risk for alcohol problems. One of the more commonly used behavioral economic measures is the Alcohol Purchase Task (APT). Although the APT has shown promise as a measure of risk for alcohol problems, the construct validity and incremental utility of the APT remain unclear. This paper presents a meta-analysis of the APT literature.

METHODS

Sixteen studies were included in the meta-analysis. Studies were gathered via searches of the PsycInfo, PubMed, Web of Science and EconLit research databases. Random-effects meta-analyses with inverse variance weighting were used to calculate summary effect sizes for each demand index-drinking outcome relationship. Moderation of these effects by drinking status (regular versus heavy drinkers) was examined. Additionally, tests of the incremental utility of the APT indices in predicting drinking problems above and beyond measuring alcohol consumption were performed.

RESULTS

The APT indices were correlated in the expected directions with drinking outcomes, although many effects were small in size. These effects were typically not moderated by the drinking status of the samples. Additionally, the intensity metric demonstrated incremental utility in predicting alcohol use disorder symptoms beyond measuring drinking.

CONCLUSIONS

The Alcohol Purchase Task appears to have good construct validity, but limited incremental utility in estimating risk for alcohol problems.

The Behavioral Economics and Neuroeconomics of Alcohol Use Disorders

BACKGROUND

Behavioral economics and neuroeconomics bring together perspectives and methods from psychology, economics, and cognitive neuroscience to understand decision making and choice behavior. Extending an operant behavioral theoretical framework, these perspectives have increasingly been applied to understand the alcohol use disorders (AUDs), and this review surveys the theory, methods, and findings from this approach. The focus is on 3 key behavioral economic concepts: delay discounting (i.e., preferences for smaller immediate rewards relative to larger delayed rewards), alcohol demand (i.e., alcohol's reinforcing value), and proportionate alcohol-related reinforcement (i.e., relative amount of psychosocial reinforcement associated with alcohol use).

FINDINGS

Delay discounting has been linked to AUDs in both cross-sectional and longitudinal studies and has been investigated cross-sectionally using neuroimaging. Alcohol demand and proportionate alcohol-related reinforcement have both been robustly associated with drinking and alcohol misuse cross-sectionally, but not over time. Both have also been found to predict treatment response to brief interventions. Alcohol demand has also been used to enhance the measurement of acute motivation for alcohol in laboratory studies. Interventions that focus on reducing the value of alcohol by increasing alternative reinforcement and response cost have been found to be efficacious, albeit in relatively small numbers of randomized controlled trials (RCTs). Mediators and moderators of response to these interventions have not been extensively investigated.

FUTURE DIRECTIONS

The application of behavioral economics and neuroeconomics to AUDs has given rise to an extensive body of empirical work, although significant gaps in knowledge remain. In particular, there is a need for more longitudinal investigations to clarify the etiological roles of these behavioral economic processes, especially alcohol demand and proportionate alcohol reinforcement. Additional RCTs are needed to extend and generalize the findings for reinforcement-based interventions and to investigate mediators and moderators of treatment success for optimization. Applying neuroeconomics to AUDs remains at an early stage and has been primarily descriptive to date, but has high potential for important translational insights into the future. The same is true for using these behavioral economic indicators to understand genetic influences on AUDs.

The behavioral economics of substance use disorders: reinforcement pathologies and their repair

The field of behavioral economics has made important inroads into the understanding of substance use disorders through the concept of reinforcer pathology. Reinforcer pathology refers to the joint effects of (a) the persistently high valuation of a reinforcer, broadly defined to include tangible commodities and experiences, and/or (b) the excessive preference for the immediate acquisition or consumption of a commodity despite long-term negative outcomes. From this perspective, reinforcer pathology results from the recursive interactions of endogenous person-level variables and exogenous environment-level factors. The current review describes the basic principles of behavioral economics that are central to reinforcer pathology, the processes that engender reinforcer pathology, and the approaches and procedures that can repair reinforcement pathologies. The overall goal of this review is to present a new understanding of substance use disorders as viewed by recent advances in behavioral economics.

A New Frontier: Integrating Behavioral and Digital Technology to Promote Health Behavior

Modifiable behavioral risk factors such as cigarette smoking, physical inactivity, and obesity contribute to over 40 % of premature deaths in the USA. Advances in digital and information technology are creating unprecedented opportunities for behavior analysts to assess and modify these risk factors. Technological advances include mobile devices, wearable sensors, biomarker detectors, and real-time access to therapeutic support via information technology. Integrating these advances with behavioral technology in the form of conceptually systematic principles and procedures could usher in a new generation of effective and scalable behavioral interventions targeting health behavior. In this selective review of the literature, we discuss how technological tools can assess and modify a range of antecedents and consequences of healthy and unhealthy behavior. We also describe practical, methodological, and conceptual advantages for behavior analysts that stem from the use of technology to assess and treat health behavior.

Behavioral economics and empirical public policy

The application of economics principles to the analysis of behavior has yielded novel insights on value and choice across contexts ranging from laboratory animal research to clinical populations to national trends of global impact. Recent innovations in demand curve methods provide a credible means of quantitatively comparing qualitatively different reinforcers as well as quantifying the choice relations between concurrently available reinforcers. The potential of the behavioral economic approach to inform public policy is illustrated with examples from basic research, pre-clinical behavioral pharmacology, and clinical drug abuse research as well as emerging applications to public transportation and social behavior. Behavioral Economics can serve as a broadly applicable conceptual, methodological, and analytical framework for the development and evaluation of empirical public policy.

Yohimbine increases opioid-seeking behavior in heroin-dependent, buprenorphine-maintained individuals

RATIONALE

In laboratory animals, the biological stressor yohimbine (α(2)-noradrenergic autoreceptor antagonist) promotes drug seeking. Human laboratory studies have demonstrated that psychological stressors can increase drug craving but not that stressors alter drug seeking.

OBJECTIVES

This clinical study tested whether yohimbine increases opioid-seeking behavior.

METHODS

Ten heroin-dependent, buprenorphine-stabilized (8 mg/day) volunteers sampled two doses of hydromorphone [12 and 24 mg IM in counterbalanced order, labeled drug A (session 1) and drug B (session 2)]. During each of six later sessions (within-subject, double-blind, randomized crossover design), volunteers could respond on a 12-trial choice progressive ratio task to earn units (1 or 2 mg) of the sampled hydromorphone dose (drug A or B) vs money ($2) following different oral yohimbine pretreatment doses (0, 16.2, and 32.4 mg).

RESULTS

Behavioral economic demand intensity and peak responding (O (max)) were significantly higher for hydromorphone 2 than 1 mg. Relative to placebo, yohimbine significantly increased hydromorphone demand inelasticity, more so for hydromorphone 1-mg units (P (max) = 909, 3,647, and 3,225 for placebo, 16.2, and 32.4 mg yohimbine doses, respectively) than hydromorphone 2-mg units (P (max) = 2,656, 3,193, and 3,615, respectively). Yohimbine produced significant but clinically modest dose-dependent increases in blood pressure (systolic ≈ 15 and diastolic ≈ 10 mmHg) and opioid withdrawal symptoms, and decreased opioid agonist symptoms and elated mood.

CONCLUSIONS

These findings concur with preclinical data by demonstrating that yohimbine increases drug seeking; in this study, these effects occurred without clinically significant subjective distress or elevated craving, and partly depended on opioid unit dose.

Latent factor structure of a behavioral economic cigarette demand curve in adolescent smokers

Behavioral economic demand curves, or quantitative representations of drug consumption across a range of prices, have been used to assess motivation for a variety of drugs. Such curves generate multiple measures of drug demand that are associated with cigarette consumption and nicotine dependence. However, little is known about the relationships among these facets of demand. The aim of the study was to quantify these relationships in adolescent smokers by using exploratory factor analysis to examine the underlying structure of the facets of nicotine incentive value generated from a demand curve measure. Participants were 138 adolescent smokers who completed a hypothetical cigarette purchase task, which assessed estimated cigarette consumption at escalating levels of price/cigarette. Demand curves and five facets of demand were generated from the measure: Elasticity (i.e., 1/α or proportionate price sensitivity); Intensity (i.e., consumption at zero price); O(max) (i.e., maximum financial expenditure on cigarettes); P(max) (i.e., price at which expenditure is maximized); and Breakpoint (i.e., the price that suppresses consumption to zero). Principal components analysis was used to examine the latent structure among the variables. The results revealed a two-factor solution, which were interpreted as "Persistence," reflecting insensitivity to escalating price, and "Amplitude," reflecting the absolute levels of consumption and price. These findings suggest a two factor structure of nicotine incentive value as measured via a demand curve. If supported, these findings have implications for understanding the relationships among individual demand indices in future behavioral economic studies and may further contribute to understanding of the nature of cigarette reinforcement.

Effects of economy type and nicotine on the essential value of food in rats

The exponential demand equation proposed by Hursh and Silberberg (2008) provides an estimate of the essential value of a good as a function of price. The model predicts that essential value should remain constant across changes in the magnitude of a reinforcer, but may change as a function of motivational operations. In Experiment 1, rats' demand for food across a sequence of fixed-ratio schedules was assessed during open and closed economy conditions and across one- and two-pellet per reinforcer delivery conditions. The exponential equation was fitted to the relation between fixed-ratio size and the logarithm of the absolute number of reinforcers. Estimates of the rate of change in elasticity of food, the proposed measure of essential value, were compared across conditions. Essential value was equivalent across magnitudes during the closed economy, but showed a slight decrease across magnitudes during the open economy. Experiment 2 explored the behavioral mechanisms of nicotine's effects on consumption with the results from Experiment 1 serving as a within-subject frame of reference. The same subjects were administered nicotine via subcutaneously implanted osmotic minipumps at a dose of 3 mg/kg/day and exposed to both the one- and two-pellet conditions under a closed economy. Although nicotine produced large decreases in demand, essential value was not significantly changed. The data from the present experiments provide further evidence for the adequacy of the exponential demand equation as a tool for quantifying the rate of change in elasticity of a good and for assessing behavioral mechanisms of drug action.

The motivation to self-administer is increased after a history of spiking brain levels of cocaine

Recent attempts to model the addiction process in rodents have focused on cocaine self-administration procedures that provide extended daily access. Such procedures produce a characteristic loading phase during which blood levels rapidly rise and then are maintained within an elevated range for the duration of the session. The present experiments tested the hypothesis that multiple fast-rising spikes in cocaine levels contribute to the addiction process more robustly than constant, maintained drug levels. Here, we compared the effects of various cocaine self-administration procedures that produced very different patterns of drug intake and drug dynamics on Pmax, a behavioral economic measure of the motivation to self-administer drug. Two groups received intermittent access (IntA) to cocaine during daily 6-h sessions. Access was limited to twelve 5-min trials that alternated with 25-min timeout periods, using either a hold-down procedure or a fixed ratio 1 (FR1). Cocaine levels could not be maintained with this procedure; instead the animals experienced 12 fast-rising spikes in cocaine levels each day. The IntA groups were compared with groups given 6-h FR1 long access and 2-h short access sessions and two other control groups. Here, we report that cocaine self-administration procedures resulting in repeatedly spiking drug levels produce more robust increases in Pmax than procedures resulting in maintained high levels of cocaine. These results suggest that rapid spiking of brain-cocaine levels is sufficient to increase the motivation to self-administer cocaine.

Poor impulse control predicts inelastic demand for nicotine but not alcohol in rats

Tobacco and alcohol dependence are characterized by continued use despite deleterious health, social and occupational consequences, implying that addicted individuals pay a high price for their use. In behavioral economic terms, such persistent consumption despite increased costs can be conceptualized as inelastic demand. Recent animal studies demonstrated that high-impulsive individuals are more willing to work for nicotine or cocaine infusions than their low-impulsive counterparts, indicating that this trait might be causally related to inelastic drug demand. By employing progressive ratio schedules of reinforcement combined with a behavioral economics approach of analysis, we determined whether trait impulsivity is associated with an insensitivity of nicotine or alcohol consumption to price increments. Rats were trained on a delayed discounting task, measuring impulsive choice. Hereafter, high- and low-impulsive rats were selected and trained to nose poke for intravenous nicotine or oral alcohol. Upon stable self-administration on a continuous reinforcement schedule, the price (i.e. response requirement) was increased. Demand curves, depicting the relationship between price and consumption, were produced using Hursh's exponential demand equation. Similar to human observations, nicotine and alcohol consumption in rats fitted this equation, thereby demonstrating the validity of our model. Moreover, high-impulsive rats displayed inelastic nicotine demand, as their nicotine consumption was less sensitive to price increments as compared with that in low-impulsive rats. Impulsive choice was not related to differences in alcohol demand elasticity. Our model seems well suited for studying nicotine and alcohol demand in rats and, as such, might contribute to our understanding of tobacco and alcohol dependence.

Some observations from behavioral economics for consideration in promoting money management among those with substance use disorders

BACKGROUND

Behavioral economics research has revealed systematic biases in decision making that merit consideration in efforts to promote money management skills among those with substance use disorders (SUDs).

OBJECTIVES

The objective of this article was to briefly review the literature on five of those biases (i.e., hyperbolic delay discounting, defaults and preference for the status quo, loss aversion, mental accounting, and failure to account for opportunity cost) that may have particular relevance to the topic of money management.

METHODS

Selected studies are reviewed to illustrate these biases and how they may relate to efforts to promote money management skills among those with substance use disorders. Studies were identified by searching PubMed using the terms "behavioral economics" and "substance use disorders", reviewing bibliographies of published articles, and discussions with colleagues.

RESULTS

Only one of these biases (i.e., hyperbolic delay discounting) has been investigated extensively among those with SUDs. Indeed, it has been found to be sufficiently prevalent among those with SUDs to be considered as a potential risk factor for those disorders and certainly merits careful consideration in efforts to improve money management skills in that population. There has been relatively little empirical research reported regarding the other biases among those with SUDs, although they appear to be sufficiently fundamental to human behavior and relevant to the topic of money management (e.g., loss aversion) to also merit consideration. There is precedent of effective leveraging of behavioral economics principles in treatment development for SUDs (e.g., contingency management), including at least one intervention that explicitly focuses on money management (i.e., advisor-teller money management therapy).

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

The consideration of the systematic biases in human decision making that have been revealed in behavioral economics research has the potential to enhance efforts to devise effective strategies for improving money management skills among those with SUDs.

Cocaine self-administration in rats: threshold procedures

Cocaine self-administration provides a methodology allowing researchers to study changes in distinct aspects of drug-taking behavior that model behaviors observed in drug addicts. Traditionally, self-administration schedules were designed to independently study changes in drug-taking behaviors (e.g., rate of responding, reinforcing efficacy, etc.). The threshold self-administration procedure was developed to measure two distinct dependent measures within the same experimental session that are important in the study of drug addiction: the maximal price an animal expends to self-administer cocaine and an animal's preferred level of cocaine consumption when available at a low behavioral cost.

The behavioral economics and neuroeconomics of reinforcer pathologies: implications for etiology and treatment of addiction

The current paper presents a novel approach to understanding and treating addiction. Drawing from work in behavioral economics and developments in the new field of neuroeconomics, we describe addiction as pathological patterns of responding resulting from the persistently high valuation of a reinforcer and/or an excessive preference for the immediate consumption of that reinforcer. We further suggest that, as indicated by the competing neurobehavioral decision systems theory, these patterns of pathological choice and consumption result from an imbalance between two distinct neurobehavioral systems. Specifically, pathological patterns of responding result from hyperactivity in the evolutionarily older impulsive system (which values immediate and low-cost reinforcers) and/or hypoactivity in the more recently evolved executive system (which is involved in the valuation of delayed reinforcers). This approach is then used to explain five phenomena that we believe any adequate theory of addiction must address.

Delayed reward discounting and addictive behavior: a meta-analysis

RATIONALE

Delayed reward discounting (DRD) is a behavioral economic index of impulsivity and numerous studies have examined DRD in relation to addictive behavior. To synthesize the findings across the literature, the current review is a meta-analysis of studies comparing DRD between criterion groups exhibiting addictive behavior and control groups.

OBJECTIVES

The meta-analysis sought to characterize the overall patterns of findings, systematic variability by sample and study type, and possible small study (publication) bias.

METHODS

Literature reviews identified 310 candidate articles from which 46 studies reporting 64 comparisons were identified (total N=56,013).

RESULTS

From the total comparisons identified, a small magnitude effect was evident (d= .15; p< .00001) with very high heterogeneity of effect size. Based on systematic observed differences, large studies assessing DRD with a small number of self-report items were removed and an analysis of 57 comparisons (n=3,329) using equivalent methods and exhibiting acceptable heterogeneity revealed a medium magnitude effect (d= .58; p< .00001). Further analyses revealed significantly larger effect sizes for studies using clinical samples (d= .61) compared with studies using nonclinical samples (d=.45). Indices of small study bias among the various comparisons suggested varying levels of influence by unpublished findings, ranging from minimal to moderate.

CONCLUSIONS

These results provide strong evidence of greater DRD in individuals exhibiting addictive behavior in general and particularly in individuals who meet criteria for an addictive disorder. Implications for the assessment of DRD and research priorities are discussed.

Self-administration of cocaine and remifentanil by monkeys: choice between single drugs and mixtures

RATIONALE

Cocaine and opioids are often co-abused. As yet, however, there is no clear evidence that the drugs interact to make the mixture a more effective reinforcer.

OBJECTIVE

The present study examined the relative reinforcing potency and maximum effectiveness of the cocaine-opioid combination in monkeys given a choice between cocaine-opioid mixtures and the single-component drugs.

METHOD

Rhesus monkeys were allowed to choose between injections of cocaine (100 μg/kg/inj) and other doses of cocaine (10-560 μg/kg/inj) or remifentanil (0.03-3.0 μg/kg/inj). A dose-addition model was used to select dose combinations for mixtures of cocaine and remifentanil predicted to be equivalent to 100 μg/kg/inj of cocaine in reinforcing effect if the drugs were additive. The monkeys were then allowed to choose between (a) cocaine and mixtures predicted to be equivalent to 100 μg/kg/inj of cocaine, (b) increasing doses of the mixtures and the single-component drugs, and (c) cocaine or remifentanil at doses that were in the highest safe range.

RESULTS

Generally, monkeys preferred the mixtures over 100 μg/kg/inj of cocaine, evidence for superadditivity. However, preferences for the mixture ceased when relatively high doses of single-component drugs were offered as alternatives. When doses within the mixture were raised and offered with relatively high doses of the single drugs, there was no clear preference for either option. The highest dose of remifentanil was chosen over the highest dose of cocaine by all monkeys.

CONCLUSION

The current results indicate that cocaine-opioid combinations can be super-additive in terms of potency, but are not, at maximum, more effective than the single-component drugs.

Effects of experimental Unemployment, Employment and Punishment analogs on opioid seeking and consumption in heroin-dependent volunteers

This study investigated the extent to which hydromorphone (HYD) choice and behavioral economic demand differed during experimental analogs of Unemployment (Drug Only: HYD and no money alternative), Employment (Drug or Money: HYD and $4 alternative), and Punishment (Drug Only+Money Loss: HYD only and $4 subtracted for each HYD choice), in the context of anticipated high vs. low post-session drug availability (HYD 24 mg vs. placebo). Eleven heroin-dependent, buprenorphine-stabilized (8 mg/day) volunteers first sampled two HYD doses (0 and 24 mg IM in randomized, counterbalanced order, labeled Drug A [session 1] and Drug B [session 2]). In each of the final six sessions, volunteers were given access to a 12-trial choice progressive ratio (PR) task and could work to receive HYD unit doses (2mg each); cumulative dose units earned were administered in a bolus injection after the work session. Before the PR task, volunteers were told which HYD dose (Drug A or B) would be available 3h after the PR-contingent injection. Relative to Unemployment (Drug Only), Employment (Drug or Money) and Punishment (Drug Only+Money Loss) each significantly suppressed HYD seeking (e.g., breakpoints). Employment and Punishment also reduced HYD behavioral economic demand, but via different mechanisms: Employment increased HYD price-elasticity, whereas Punishment decreased HYD demand intensity. Adjusting for the initial level difference (i.e., normalized demand), Employment significantly decreased P(max) (i.e., lower "essential value" of HYD) and O(max) (maximum HYD responding) compared to Punishment or Unemployment. These effects were not significantly altered by post-session drug availability.

Predictors of motivation for abstinence at the end of outpatient substance abuse treatment

Commitment to abstinence, a motivational construct, is a strong predictor of reductions in drug and alcohol use. Level of commitment to abstinence at treatment end predicts sustained abstinence, a requirement for recovery. This study sought to identify predictors of commitment to abstinence at treatment end to guide clinical practice and to inform the conceptualization of motivational constructs. Polysubstance users (N = 250) recruited at the start of outpatient treatment were reinterviewed at the end of services. Based on the extant literature, potential predictors were during treatment measures of substance use and related cognitions, psychological functioning, recovery supports, stress, quality of life satisfaction, and treatment experiences. In multivariate analyses, perceived harm of future drug use, abstinence self-efficacy, quality of life satisfaction, and number of network members in 12-step recovery contributed 26.6% of the variance explained in the dependent variable, a total of 49.6% when combined with the control variables (demographics and baseline level of the outcome). Gender subgroup analyses yielded largely similar results. Clinical implications of findings for maximizing commitment to abstinence when clients leave treatment are discussed as are future research directions.