Polydrug abuse in heroin addicts: a behavioral economic analysis

Contextual and psychosocial factors influencing drug reward in humans: The importance of non-drug reinforcement

The reinforcing efficacy, or behavior-strengthening effect, of a substance is a critical determinant of substance use typically quantified by measuring behavioral allocation to the substance under schedules of reinforcement with escalating response requirements. Although responses on these tasks are often used to indicate stable reinforcing effects or trait-level abuse potential for an individual, task designs often demonstrate within-person variability across varying degrees of a constraint within experimental procedures. As a result, quantifying behavioral allocation is an important way to measure the impact of contextual and psychosocial factors on substance reward. We review studies using laboratory self-administration, behavioral economic purchase tasks, and ambulatory assessments to quantify the impact of various contextual and psychosocial factors on behavioral allocation toward consumption of a substance. We selected these assessment approaches because they cover the translational spectrum from experimental control to ecological relevance, with consistent support across these approaches representing greater confidence in the effect. Conceptually, we organized factors that influence substance value into two broad categories: factors that influence the cost/benefit ratio of the substance (social context, stress and affect, cue exposure), and factors that influence the cost/benefit ratio of an alternative (alternative non-drug reinforcers, alternative drug reinforcers, and opportunity costs). We conclude with an overview of future research directions and considerations for clinical application.

Impacts of xylazine on fentanyl demand, body weight, and acute withdrawal in rats: A comparison to lofexidine

The opioid use landscape has recently shifted to include xylazine, a veterinary anesthetic, as an adulterant in the fentanyl supply. The health impacts of xylazine as an emerging fentanyl adulterant has raised alarm regarding xylazine as a public health threat, warranting research on the impacts of xylazine on fentanyl's behavioral effects. No prior studies have evaluated the effects of xylazine on fentanyl consumption at various unit doses, fentanyl demand, or withdrawal as compared to the Food and Drug Administration-approved opioid withdrawal medication, lofexidine (Lucemyra®). This is important because lofexidine and xylazine are both adrenergic α2a (A2aR) agonists, however, lofexidine is not a noted fentanyl adulterant. Here we evaluated xylazine and lofexidine combined with self-administered fentanyl doses in male and female rats and evaluated fentanyl demand, body weight, and acute withdrawal. Consumption of fentanyl alone increased at various unit doses compared to saline. Xylazine but not lofexidine shifted fentanyl consumption downward at a number of unit doses, however, both lofexidine and xylazine suppressed fentanyl demand intensity as compared to a fentanyl alone control group. Further, both fentanyl + lofexidine and fentanyl + xylazine reduced behavioral signs of fentanyl withdrawal immediately following SA, but signs increased by 12 h only in the xylazine co-exposed group. Weight loss occurred throughout fentanyl SA and withdrawal regardless of group, although the xylazine group lost significantly more weight during the first 24 h of withdrawal than the other two groups. Severity of weight loss during the first 24 h of withdrawal was also correlated with severity of somatic signs of fentanyl withdrawal. Together, these results suggest that body weight loss may be an important indicator of withdrawal severity during acute withdrawal from the xylazine/fentanyl combination, warranting further translational evaluation.

Using behavioral economics to optimize safer undergraduate late-night transportation

Many universities sponsor student-oriented transit services that could reduce alcohol-induced risks but only if services adequately anticipate and adapt to student needs. Human choice data offer an optimal foundation for planning and executing late-night transit services. In this simulated choice experiment, respondents opted to either (a) wait an escalating delay for a free university-sponsored "safe" option, (b) pay an escalating fee for an on-demand rideshare service, or (c) pick a free, immediately available "unsafe" option (e.g., ride with an alcohol-impaired driver). Behavioral-economic nonlinear models of averaged-choice data describe preference across arrangements. Best-fit metrics indicate adequate sensitivity to contextual factors (i.e., wait time, preceding late-night activity). At short delays, students preferred the free transit option. As delays extend beyond 30 min, most students preferred competing alternatives. These data depict a policy-relevant delay threshold to better safeguard undergraduate student safety.

A contextualized reinforcer pathology approach to addiction

Behavioural economic accounts of addiction conceptualize harmful drug use as an operant reinforcer pathology, emphasizing that a drug is consumed because of overvaluation of smaller immediate rewards relative to larger delayed rewards (delay discounting) and high drug reinforcing value (drug demand). These motivational processes are within-individual determinants of behaviour. A third element of learning theory posits that harmful drug use depends on the relative constraints on access to other available activities and commodities in the choice context (alternative reinforcers), reflecting the substantial influence of environmental factors. In this Perspective, we integrate alternative reinforcers into the contemporary behavioural economic account of harmful drug use - the contextualized reinforcer pathology model - and review empirical literature across the translational spectrum in support of this model. Furthermore, we consider how increases in drug-related mortality and health disparities in addiction can be understood and potentially ameliorated via a contextualized reinforcer pathology model in which lack of alternative reinforcement is a major risk factor for addiction.

Anhedonia modulates benzodiazepine and opioid demand among persons in treatment for opioid use disorder

Background

Benzodiazepine (BZD) misuse is a significant public health problem, particularly in conjunction with opioid use, due to increased risks of overdose and death. One putative mechanism underlying BZD misuse is affective dysregulation, via exaggerated negative affect (e.g., anxiety, depression, stress-reactivity) and/or impaired positive affect (anhedonia). Similar to other misused substances, BZD consumption is sensitive to price and individual differences. Although purchase tasks and demand curve analysis can shed light on determinants of substance use, few studies have examined BZD demand, nor factors related to demand.

Methods

This ongoing study is examining simulated economic demand for alprazolam (among BZD lifetime misusers based on self-report and DSM-5 diagnosis; n = 23 total; 14 male, 9 female) and each participant's preferred-opioid/route using hypothetical purchase tasks among patients with opioid use disorder (n = 59 total; 38 male, 21 female) who are not clinically stable, i.e., defined as being early in treatment or in treatment longer but with recent substance use. Aims are to determine whether: (1) BZD misusers differ from never-misusers on preferred-opioid economic demand, affective dysregulation (using questionnaire and performance measures), insomnia/behavioral alertness, psychiatric diagnoses or medications, or urinalysis results; and (2) alprazolam demand among BZD misusers is related to affective dysregulation or other measures.

Results

Lifetime BZD misuse is significantly (p < 0.05) related to current major depressive disorder diagnosis, opioid-negative and methadone-negative urinalysis, higher trait anxiety, greater self-reported affective dysregulation, and younger age, but not preferred-opioid demand or insomnia/behavioral alertness. Alprazolam and opioid demand are each significantly positively related to higher anhedonia and, to a lesser extent, depression symptoms but no other measures of negative-affective dysregulation, psychiatric conditions or medications (including opioid agonist therapy or inpatient/outpatient treatment modality), or sleep-related problems.

Conclusion

Anhedonia (positive-affective deficit) robustly predicted increased BZD and opioid demand; these factors could modulate treatment response. Routine assessment and effective treatment of anhedonia in populations with concurrent opioid and sedative use disorder may improve treatment outcomes.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT03696017, identifier NCT03696017.

Synthetic cannabinoids awareness among patients with opioid use disorder in Serbia - A survey based cross-sectional pilot study

Introduction

There is limited data on the awareness and use of synthetic cannabinoids (SCs) in high-risk population in Serbia, despite SCs becoming more and more common at illicit drug market.

Aim

This pilot study aimed to examine the awareness and prevalence of use of SCs in patients with an opioid-use disorder and to identify patient characteristics and other factors associated with SCs use.

Patients and methods

This cross-sectional study was conducted at the Clinic for Psychiatry, Clinical Center Vojvodina, Serbia, the largest tertiary health care institution in this region of the country. All patients hospitalized due to the treatment of opioid dependence during November and December 2017 were included (response rate 100%), and filled-out an anonymous questionnaire specifically developed for the purpose of this study. Differences between patients reporting SCs use and those who did not were compared using chi-square test with values of p < 0.05 were considered significant.

Results

Out of 64 patients (median age 36.37 years), one third (32.81%) reported using SCs. Socio-demographic characteristics of the subjects were not associated with SCs use. There were differences in the most common sources of information reported between the SCs users and non-users. Majority of SCs users (76.0%) were informed about SCs through friends, compared with just 26.0% of non-users (<0.001). Nearly all study participants (93.8%) were daily tobacco users. The share of respondents reporting alcohol and marihuana use was significantly higher among the SCs users (52.0% vs. 20.9%, p = 0.011 and 15.6% vs. 12.5%, p = 0.015), respectively. Higher share of SCs users used multiple psychoactive substances (38.1% vs. 16.3%), and this difference was statistically significant (p = 0.047). The most commonly reported adverse effect of SCs among users included dry mouth (81.0%), trouble thinking clearly (52.4%) and panic attacks (52.4%).

Conclusion

Understanding the awareness and use of SCs among high-risk drug users, as well as associated factors can help improve substance-use disorder treatment in our setting. Educational activities targeting public are urgently needed to raise awareness on SCs, considering that social contacts are the main sources of information on SC for this vulnerable population. Users of SCs have also reported using other psychoactive substances more often, and this calls for a holistic approach addressing multiple factors to improve substance-use treatment in our setting.

Reinforcer pathology of internet-related behaviors among college students: Data from six countries

Research has demonstrated that repeated engagement in low-effort behaviors that are associated with immediate reward, such as Internet use, can result in a pathological reinforcement process in which the behavior is increasingly selected over other activities due, in part, to a low availability of alternative activities and to a strong preference for immediate rather than delayed rewards (delay discounting). However, this reinforcer pathology model has not been generalized to other Internet-related behaviors, such as online gaming or smartphone use. Given the widespread availability of these technologies, it is also important to examine whether reinforcer pathology of Internet-related behaviors is culturally universal or culture-specific. The current study examines relations between behavioral economic constructs (Internet demand, delay discounting, and alternative reinforcement) and Internet-related addictive behaviors (harmful Internet use, smartphone use, online gaming, and Internet sexual behavior) in a cross-sectional sample of college students (N = 1,406) from six different countries (Argentina, Australia, India, Malaysia, the United Kingdom, and the United States). Using structural equation modeling, Internet demand was associated with harmful Internet use, smartphone use, and online gaming; delay discounting was associated with harmful smartphone use; and alternative reinforcement was associated with harmful Internet and smartphone use. The models were partially invariant across countries. However, mean levels of behavioral economic variables differed across countries, country-level gross domestic product, person-level income, and sex at birth. Results support behavioral economic theory and highlight the importance of considering both individual and country-level sociocultural contextual factors in models for understanding harmful engagement with Internet-related behaviors. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

New Psychoactive Substances Consumption in Opioid-Use Disorder Patients

Simple Summary

We applied a toxicological screening on 187 urine samples collected from patients with opioid-use disorder treated with opioid agonists in Barcelona and Badalona addiction care services, Spain. We found that 27.3% of urine samples were positive for any type of new psychoactive substance and 8.6% of samples were positive for a new synthetic opioid (NSO). These results show a new trend of consumption in patients with opioid-use disorder that requires social and political actions to stem associated health threats.

Abstract

(1) Background: Since the beginning of the 21st century, the large number and wide chemical variety of new psychoactive substances (NPS) that enter the market every year has become a public health problem. Given the rapidity with which the drug market is changing, many NPS are not clinically investigated and their effects and health risks are unknown. Drug testing is a very useful tool for this purpose, but, unfortunately, it is not very widespread in individuals with opioid-use disorder under detoxification treatment. The aim of this study is to investigate the use of illicit drugs and NPS in opioid-use disorder (OUD) patients on opioid agonist treatment. (2) Methods: A multicenter, descriptive, cross-sectional study was conducted at two addiction care services in Barcelona and Badalona, Spain. Urine samples were collected from OUD individuals attending these two centers, who anonymously donated a urine sample at the time of a periodical visit. Samples were analyzed by high-sensitivity gas chromatography-mass spectrometry (GC-MS) and ultra-high-performance liquid chromatography-high –resolution mass spectrometry (UHPLC-HRMS). (3) Results: Out of the 187 collected and analyzed urine samples, 27.3% were positive for any type of NPS and 8.6% were positive for new synthetic opioids, including fentanyl and its derivatives (NSO). Other frequently detected substances were benzodiazepines in 46.0% of samples, antipsychotics in 27.8% of samples, or cocaine and cannabis in 23.5% of samples. (4) Conclusion: A wide number of NPS, including NSO, have been detected in urine samples from an OUD population. A lack of NPS detection in standard drug screening among drug users can hide the identification of a potential public health problem.

Behavioral economics of substance use: Understanding and reducing harmful use during the COVID-19 pandemic

Behavioral economic research demonstrates that alcohol and drug consumption is (a) an inverse function of constraints on access to the substance and (b) a direct function of constraints on access to alternative rewards. Physical distancing interventions and economic consequences of the COVID-19 pandemic have resulted in unprecedented reductions in many of the constraints on substance use and in critical evolutionarily salient sources of alternative reward, such as social interaction, physical activity, leisure activities and hobbies, and academic and occupational pursuits. Thus, behavioral economics suggests that the pandemic and necessary public health response have created a "perfect storm" for exacerbation of individual-level and population-level substance use problems and also points to multilevel intervention strategies. We summarize this perspective and research by highlighting 3 critical behavioral processes that will influence drug and alcohol consumption. First, the sudden absence of many effective constraints on substance use (work, school, community, or service obligations) will reduce the actual and perceived cost of use. Second, physical distancing measures will reduce the availability, and increase the cost, of many rewarding substance-free activities and commodities. Third, increased uncertainty around current and future events increases discounting of delayed rewards. These effects will be especially pernicious among populations with existing health disparities. Next, we outline interventions suggested by behavioral economics to mitigate the impact of COVID-19 on substance use that are aimed at increasing perceived costs of use; increasing access to substance-free activities, including treatment; and lengthening the timeframe for behavioral allocation and altering environmental contexts to promote healthy choices. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Concurrent validity of the Alcohol Purchase Task for measuring the reinforcing efficacy of alcohol: an updated systematic review and meta-analysis

BACKGROUND AND AIMS

An early meta-analysis testing the concurrent validity of the Alcohol Purchase Task (APT), a measure of alcohol's relative reinforcing value, reported mixed associations, but predated a large number of studies. This systematic review and meta-analysis sought to: (1) estimate the relationships between trait-based alcohol demand indices from the APT and multiple alcohol indicators, (2) test several moderators and (3) analyze small study effects.

METHODS

A meta-analysis of 50 cross-sectional studies in four databases (n = 18 466, females = 43.32%). Sex, year of publication, number of APT prices and index transformations (logarithmic, square root or none) were considered as moderators. Small study effects were examined by using the Begg-Mazumdar, Egger's and Duval & Tweedie's trim-and-fill tests. Alcohol indicators were quantity of alcohol use, number of heavy drinking episodes, alcohol-related problems and hazardous drinking. APT indices were intensity (i.e. consumption at zero cost), elasticity (i.e. sensitivity to increases in costs), O_max (i.e. maximum expenditure), P_max (i.e. price associated to O_max ) and breakpoint (i.e. price at which consumption ceases).

RESULTS

All alcohol demand indices were significantly associated with all alcohol-related outcomes (r = 0.132-0.494), except P_max , which was significantly associated with alcohol-related problems only (r = 0.064)_. The greatest associations were evinced between intensity in relation to alcohol use, hazardous drinking and heavy drinking and between O_max and alcohol use. All the tested moderators emerged as significant moderators. Evidence of small-study effects was limited.

CONCLUSIONS

The Alcohol Purchase Task appears to have concurrent validity in alcohol research. Intensity and O_max are the most relevant indices to account for alcohol involvement.

Decreased cocaine demand following contingency management treatment

A hypothetical cocaine purchasing task (CocPT) was used to assess changes in cocaine demand in the context of contingency management (CM) treatment for cocaine use disorder (CUD). Participants (N = 89) were treatment-seeking individuals with CUD receiving 4 weeks of abstinence-based, high-magnitude CM. Treatment response (vs. non-response) was operationally defined as the submission of 6 consecutive cocaine-negative urine samples across two weeks. The CPT was assessed at baseline, week 2, and week 5. Demand data were well described by the exponentiated demand model, and baseline demand indices (Q0, Pmax, breakpoint, essential value) were significantly associated with self-report measures of cocaine use. The probability of being a zero-responder reporting zero cocaine consumption at all prices significantly increased over the course of treatment, and was greater among treatment responders vs. non-responders. Among non-zero demand data, decreases in Omax, Pmax, breakpoint, and essential value were observed over the course of CM treatment, favoring responders. To our knowledge, this is the first study to assess change in cocaine demand in the context of CM treatment targeting cocaine abstinence. Our results support the utility of cocaine demand as a measure for both identifying individuals with greater treatment need and tracking relapse risk over the course of treatment.

Assessment of demand for methamphetamine and cigarettes among individuals with methamphetamine use disorder

Methamphetamine (MA) is a highly addictive stimulant with recent upward trends in prevalence and associated public health problems. Drug demand, as assessed by hypothetical purchasing tasks, has been useful in addictions research and may help our understanding of the factors influencing MA use. However, no studies have assessed MA demand using current models of demand. The purpose of the current study was to assess demand for MA using a hypothetical drug purchasing task. Given high rates of cigarette smoking among MA users, it was of interest also to assess and compare demand for MA relative to cigarettes. Participants consisted of non-treatment-seeking volunteers with MA use disorder (N = 18), of whom 17 reported daily smoking. Results showed the exponentiated demand model provided a good fit to consumption data. Results from Bayesian generalized linear modeling demonstrated multiple positive relationships (posterior probability ≥75%) between self-reported drug use (days MA used in the past 30 days, cigarettes smoked per day) and indices of demand for each drug (Qo, Omax, Pmax, and break point). Comparing MA to cigarettes, results from Bayesian generalized linear mixed modeling revealed greater abuse liability for MA compared to cigarettes (posterior probability ≥99%) based on α and essential value. Overall, the findings of the current study support the feasibility and validity of the exponentiated demand model for assessing demand for drugs among individuals with MA use disorder. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Subjective symptoms and serum methadone concentrations: what should guide dose adjustments in methadone maintenance treatment? A naturalistic cohort study from Norway

BACKGROUND

There is little evidence-based guidance on how to optimize methadone dosages among patients with opioid addiction undergoing methadone maintenance treatment (MMT). This study aims to investigate whether self-perceived opioid withdrawal symptoms, adverse effects, and self-reported substance use in patients on MMT are related to serum methadone concentrations and the role that these variables could play in clinical decisions on dose adjustments.

METHODS

This naturalistic prospective cohort study included clinical and laboratory measurements from 83 patients undergoing MMT in outpatient clinics in Bergen, Norway, from May 2017 to January 2020. Information on age, gender, methadone daily doses and serum concentrations, subjective opioid withdrawal symptoms using 16 items Subjective Opioid Withdrawal Scale (SOWS) questionnaire, self-reported adverse effects, and substance use was obtained. Linear mixed modelling was used for analyzing the data.

RESULTS

The mean age of the participants was 45 years, and 33% were women. Almost half reported mild to moderate subjective opioid withdrawal symptoms, and all had experienced at least one subjective adverse effect. The use of at least one substance was reported by 88% of the participants. Serum concentration-to-dose ratios were lower among those who had reported subjective opioid withdrawal symptoms (p) = 0.039). The total SOWS score (p < 0.001); the specific subjective withdrawal symptoms of anxiety (p = 0.004), bone and muscle aches (p = 0.003), restlessness (p = 0.017), and (slightly) shaking (p = 0.046), also use of heroin (p = 0.015) and alcohol (p = 0.011) were associated with lower methadone concentrations. Cannabis use was slightly related to higher methadone concentrations (p = 0.049).

CONCLUSIONS

The findings suggest that the patient's self-perceived symptoms and current clinical condition are related to the serum concentrations of methadone. This interpretation supports dose adjustments based on patient-reported symptoms. In some aberrant cases, measurement of serum concentrations together with other individual assessments may be considered to support the clinical decision.

Behavioral economic demand in opioid treatment: Predictive validity of hypothetical purchase tasks for heroin, cocaine, and benzodiazepines

BACKGROUND

Behavioral economics provides a framework in which to understand choice and motivation in the field of substance use disorders. Hypothetical purchase tasks (HPT), which indicate the amount or probability of purchasing substances at different prices, have been suggested as a clinical tool that can help predict future substance use and identify targets for intervention.

METHODS

Hypothetical demand for heroin, cocaine, and benzodiazepines was assessed at baseline and after six-months in 52 opioid-agonist treatment patients. The results were analyzed using a novel exponential demand equation (normalized zero-bounded exponential model [ZBEn]) that uses a log-like transform that accommodates zero consumption values.

RESULTS

Demand for these drugs was well described by the ZBEn model. After six months, demand intensity for heroin was decreased and demand metrics for cocaine and benzodiazepines increased. Multiple demand curve indices at baseline predicted the percentage of drug-positive urinalysis results at follow-up, even after controlling for covariates. Additionally, participants were divided into High and Low baseline demand groups for each drug based on demand indices. Participants with High demand at baseline for 8 out of 9 groups had significantly more drug-positive urine samples in the subsequent 6-month period.

CONCLUSIONS

This report provides evidence that demand assessment is predictive of future substance use and could help guide treatment planning at intake. These results also demonstrated that the ZBEn model provides good fits to consumption data and allows for sensitive statistical analyses.

Demand curve analysis of marijuana use among persons living with HIV

BACKGROUND

Despite medicalization and legalization of marijuana use, factors influencing demand for marijuana among persons living with HIV (PLWH) are incompletely understood. This knowledge gap undermines effective clinical management and policies. This study used demand curve simulation methods to address these issues.

METHODS

Marijuana-using PLWH (N = 119) completed experimental tasks to simulate amount of marijuana purchasing/use across different costs (money or time), and likelihood of reselling marijuana or marijuana therapeutic-use registration card in relation to profits. Additional simulations assessed purchasing of marijuana relative to other drug and non-drug goods.

RESULTS

Simulated marijuana use decreased as money and time costs increased. Consumption was greater for participants with more severe Cannabis Use Disorder (CUD) and anxiety, intermediate pain levels, and past 90-day opioid use. Whereas few participants chose to sell their registration card, marijuana resale (diversion) steeply increased with profit. Likelihood of seeking marijuana therapeutic-use certification decreased in relation to registration card money cost, having to visit more physicians to get a signature, and delay to receiving the card, and increased with duration of certification. Participants who reported recent opioid use were more likely to seek certification. Consumption of several commodities assessed was independent of marijuana.

CONCLUSIONS

Simulated marijuana use was related to participants' clinical profile (CUD, anxiety and pain symptoms, recent opioid use), and unrelated to purchasing other goods. Likelihood of seeking marijuana therapeutic-use registration was affected by several types of costs and recent opioid use. Participants were unlikely to divert registration cards. We discuss clinical and policy implications of these findings.

Episodic future thinking for smoking cessation in individuals with substance use disorder: Treatment feasibility and acceptability

BACKGROUND

Smokers with substance use disorders (SUD) smoke approximately four times more than the general population. Current efforts are focused on improving smoking cessation treatments for this population. Episodic future thinking (EFT), a novel intervention aimed at decreasing impulsive choice, has shown promising results for reducing cigarette demand in experimental settings. This feasibility study sought to examine the feasibility and preliminary EFT effects on delay discounting (DD) and nicotine intake reductions throughout treatment.

METHOD

Smokers in substance use treatment (N = 29; 75.9% males) received an 8-week cognitive-behavioral treatment (CBT) + EFT for smoking cessation. The study assessed feasibility through successful recruitment rates, retention, and adherence to treatment. Participants' satisfaction acted as our acceptability measure. We computed nonparametric range tests to analyze changes in continuous variables.

RESULTS

Among interested individuals, 42 (43.75%) met the inclusion criteria, and 29 entered the treatment program. Rate of treatment completion was 65.5% (19/29). Mean (SD) sessions attended were 7(1.11), and mean patient satisfaction rating with treatment was 8.83/10. The study observed low compliance with EFT, with 15.8% (3/19) of patients practicing at least 50% of the requested times.

CONCLUSIONS

CBT + EFT is acceptable for the SUD population. However, future studies should implement some adjustments to improve the adherence and feasibility of EFT, such as reducing the number of practices and temporal intervals in EFT events. Given the small sample size, and the absence of a control group, future larger scale trials are needed to elucidate EFT effects on DD and smoking cessation.

Purchase task sensitivity to drug and nondrug reinforcers in opioid-agonist treatment patients

The behavioral economics of substance abuse has been increasingly recognized as a method of determining the value of abused substances for individuals who use those substances. It has been hypothesized that such analyses could serve as a clinical tool and that demand functions can be targeted predictors for the level of intervention necessary. This study evaluated the sensitivity of a demand task in 2 patient groups in a medication assisted treatment program (methadone maintenance), those who had used opioids in the last 2 months and those who had not used opioids in at least 18 months. Demand for 7 drugs and a control was assessed using hypothetical purchase tasks. Participants maintaining long-term abstinence had significantly higher α (sensitivity to price) and lower Q₀ (intensity of demand) for heroin than participants who had recently used opioids. Further research is necessary to illustrate if treatment is responsible for this reduction in demand. If so, demand analyses may provide clinical utility as an aid for treatment planning or as a target for treatment.

Sex moderates the effects of experimentally induced musculoskeletal pain on alcohol demand in healthy drinkers

BACKGROUND

Pain may serve as an antecedent for alcohol use, increasing risk for hazardous drinking and associated consequences. Delayed onset muscle soreness (DOMS) induction produces clinically relevant but time-limited musculoskeletal pain. This study was conducted to determine whether DOMS induction on the dominant elbow flexors influenced alcohol demand using the Alcohol Purchase Task (APT). We hypothesized DOMS would increase alcohol demand relative to a sham control. Based on existing studies of pain self-medication, we expected DOMS-related increases in alcohol demand would be greatest in men.

METHODS

Participants (N = 53; 57 % women) were randomly assigned to a DOMS (eccentric exercise) or sham condition (concentric exercise). Participants completed the APT pre-exercise and 48 -hs post-exercise. Repeated measures GLM was used to characterize group by sex by time interactions on APT indices, including intensity, breakpoint, essential value (EV), O_max, and P_max.

RESULTS

The DOMS procedure significantly increased pain ratings at the elbow flexors. Men had significantly higher demand intensity than women across groups and time points. Significant interactive effects were detected for breakpoint and EV. From pre- to post-test, breakpoint significantly increased in men in the DOMS group. However, breakpoint and EV significantly decreased in women in the DOMS group.

CONCLUSIONS

Increased alcohol demand in men in the DOMS group was consistent with epidemiological data suggesting men are at higher risk for self-medicating pain with alcohol than women. However, decreased demand in women was unexpected. Taken together, results indicate DOMS induction may be a useful means to characterize pain as an antecedent for alcohol use.

Why Switch? - Motivations for Self-Substitution of Illegal Drugs

Self-substitution is the conscious switch from one drug to another for reasons such as price, availability, desired effect, or perceived benefit of the substitute drug. Purpose/Objectives: This study aimed to describe drug use patterns and motivations associated with substitution. We examined correlates of lifetime substitution among individuals with substance use disorder. Methods: A cross-sectional study of 771 treatment-enrolled individuals. We used self-report for determining the lifetime prevalence, correlates, and motivations for substitution. Results: Of the 771 respondents, 570 (73.9%) reported ever substituting their preferred substance. The main incentives for substitution were availability (23.7%) and curiosity (20.2%). Among heroin or cannabis preferers, improved effects or less adverse effects of the substitute drug, self-medication, and managing withdrawal symptoms were significant substitution incentives. Increased odds for substitution were observed for past 12 months use of cannabis (OR = 1.51, CI = 1.06-4.52), prescription opioids (OR = 2.86, CI = 1.81-4.52), novel psychoactive substances (OR = 2.68, CI = 1.64-4.36), and repeated admission (OR = 1.50, CI = 1.05-2.14). Older age at onset-of-use was negatively associated with substitution (OR = 0.95, CI = 0.93-0.98). Conclusions: Self-substitution of one substance for another is a highly prevalent behavior among treatment-enrolled patients with substance use disorder. Clinicians caring for substance use disorder patients should be aware of substitution patterns involving the use of highly potent substances, which constitutes a risk to patients. Results underscore the benefit of substitution patterns analyses, as they reveal important information on the characteristics of persons who use drugs and their motivations.

The switch from one substance-of-abuse to another: illicit drug substitution behaviors in a sample of high-risk drug users

Background

Substitution can be defined as the consciously motivated choice to use one drug, either licit or illicit, instead of another, due to perceptions of cost, availability, safety, legality, substance characteristics, and substance attributions. Substitution represents a potential risk to drug users, mainly when substitutes are of higher potency and toxicity. This study offers a basic conceptualization of illicit substitution behavior and describes substitution patterns among users of two highly prevalent drugs of abuse-heroin and cannabis.

Methods

Here, 592 high-risk drug users undergoing pharmacological and psycho-social treatment were interviewed. Patients were asked questions about current drug use, lifetime substitution, and substitution patterns. Descriptive statistics, chi-square tests of independence, and multinomial logistic regressions were used to identify and test correlates of substitution patterns for heroin and cannabis.

Results

Of the 592 drug users interviewed, 448 subjects (75.7%) reported having substituted their preferred drug for another illicit substance. Interviews yielded a total of 275 substitution events reported by users of cannabis, and 351 substitution events reported by users of heroin. The most frequently reported substitution substances for responders who preferred heroin were illicit non-prescribed "street" methadone (35.9%), followed by oral and transdermal prescription opioids (17.7%). For responders who preferred cannabis, substitution for synthetic cannabinoid receptor agonists (33.5%) followed by alcohol (16.0%) were the most commonly reported. Age at onset-of-use (p < 0.005), population group (p = 0.008), and attending treatment for the first time (p = 0.026) were significantly associated with reported lifetime substitution. Past-year use of stimulants, heroin, hallucinogens, methylenedioxymethamphetamine (MDMA), and novel psychoactive substances were-at the 95% confidence level-also significantly associated with reported lifetime substitution. In multivariate analysis, the odds for methadone substitution among heroin users were significantly affected by age at onset-of-use, type of treatment center, and education. Odds for substitution for synthetic cannabinoid receptor agonists among cannabis users were significantly affected by age, population group, type of treatment center, and education.

Conclusion

Self-substitution behavior should be considered by clinicians and policymakers as a common practice among most drugusers. Substitution for street methadone provides evidence for the ongoing diversion of this substance from Opioid Maintenance Treatment Centers, while the prominence of substitution of synthetic cannabinoids among dual-diagnosis patients should be regarded as an ongoing risk to patients that needs to be addressed by clinicians. Analysis of additional substitution patterns should provide further valuable insights into the behavior of drugusers.

One Is Not Enough: Understanding and Modeling Polysubstance Use

Substance use disorder (SUD) is a chronic, relapsing disease with a highly multifaceted pathology that includes (but is not limited to) sensitivity to drug-associated cues, negative affect, and motivation to maintain drug consumption. SUDs are highly prevalent, with 35 million people meeting criteria for SUD. While drug use and addiction are highly studied, most investigations of SUDs examine drug use in isolation, rather than in the more prevalent context of comorbid substance histories. Indeed, 11.3% of individuals diagnosed with a SUD have concurrent alcohol and illicit drug use disorders. Furthermore, having a SUD with one substance increases susceptibility to developing dependence on additional substances. For example, the increased risk of developing heroin dependence is twofold for alcohol misusers, threefold for cannabis users, 15-fold for cocaine users, and 40-fold for prescription misusers. Given the prevalence and risk associated with polysubstance use and current public health crises, examining these disorders through the lens of co-use is essential for translatability and improved treatment efficacy. The escalating economic and social costs and continued rise in drug use has spurred interest in developing preclinical models that effectively model this phenomenon. Here, we review the current state of the field in understanding the behavioral and neural circuitry in the context of co-use with common pairings of alcohol, nicotine, cannabis, and other addictive substances. Moreover, we outline key considerations when developing polysubstance models, including challenges to developing preclinical models to provide insights and improve treatment outcomes.

Experimental manipulations of behavioral economic demand for addictive commodities: a meta-analysis

BACKGROUND AND AIMS

Reinforcing value, an index of motivation for a drug, is commonly measured using behavioral economic purchase tasks. State-oriented purchase tasks are sensitive to phasic manipulations, but with heterogeneous methods and findings. The aim of this meta-analysis was to characterize the literature examining manipulations of reinforcing value, as measured by purchase tasks and multiple-choice procedures, to inform etiological models and treatment approaches METHODS: A random-effects meta-analysis of published findings in peer-reviewed articles. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol, studies were gathered through searches in PsycINFO and PubMed/MEDLINE (published 22 May 2018). Searches returned 34 unique studies (aggregate sample n = 2402; average sample size = 68.94) yielding 126 effect sizes. Measurements included change (i.e. Cohen's d) in six behavioral economic indices (intensity, breakpoint, O_max , P_max , elasticity, cross-over point) in relation to six experimental manipulations (cue exposure, stress/negative affect, reinforcer magnitude, pharmacotherapy, behavioral interventions, opportunity cost).

RESULTS

Cue exposure (d range = 0.25-0.44, all Ps < 0.05) and reinforcer magnitude [d = 0.60; 95% confidence interval (CI) = 0.18, 1.01; P < 0.005] manipulations resulted in significant increases in behavioral economic demand across studies. Stress/negative affect manipulations also resulted in a small, significant increase in O_max (d = 0.18; 95% CI = 0.01, 0.34; P = 0.03); all other effect sizes for negative affect/stress were non-significant, albeit similar in size (d range = 0.14-0.18). In contrast, pharmacotherapy (d range = -0.37 to -0.49; Ps < 0.04), behavioral intervention (d = -0.36 to -1.13) and external contingency (d = -1.42; CI = -2.30, -0.54; P = 0.002) manipulations resulted in a significant decrease in intensity. Moderators (substance type) explained some of the heterogeneity in findings across meta-analyses.

CONCLUSIONS

In behavioral economic studies, purchase tasks and multiple-choice procedures appear to provide indices that are sensitive to manipulations found to influence motivation to consume addictive substances in field experiments.

The Hotel Room Purchase Task: Effects of Gender and Partner Desirability on Demand for Hypothetical Sex in Individuals with Disordered Cocaine Use and Controls

Hypothetical purchase tasks allow for rapid assessment of behavioral economic demand for numerous commodities and are useful in evaluating reinforcer pathologies, such as substance and behavioral addiction. Currently, there is not a task for evaluating demand for sex without requiring implicit engagement in sex work. The current study used a novel purchase task with hotel rooms for sex as the hypothetical commodity to assess demand for sex in individuals with disordered cocaine use, a population that frequently engages in risky sexual behavior. Adults meeting criteria for cocaine abuse or dependence (13 males, ten females) and noncocaine-using controls (eight males, three females) chose hypothetical sexual partners from a series of photographs and endorsed two partners with whom they would most and least like to have sex. Participants then completed the hotel purchase task for both partners, wherein they reported how many nights at a hotel room, at prices from $10 to $1280 per night, they would purchase in a year. Demand intensity was significantly greater and demand elasticity was significantly lower for the most preferred relative to the less preferred partner. Males demonstrated significantly greater intensity and lesser elasticity for sex than females. Demand metrics did not differ between the cocaine and control group. This task may serve as a useful measure of demand for sex without requiring implicit hypothetical engagement in sex work. Future studies exploring the relation between task performance and other characteristics such as sexual dysfunction, in addition to acute substance administration effects, may further determine the task's clinical utility.

Utilizing the commodity purchase task to evaluate behavioral economic demand for illicit substances: a review and meta-analysis

BACKGROUND ANDAIMS

The commodity purchase task is a simulated demand procedure that is easy and quick to complete (< 5 minutes) as well as adaptable for remote delivery and use with varied study populations. The purpose of this meta-analysis was to synthesize research using the commodity purchase task with illicit substances to evaluate the magnitude of omnibus effects sizes and moderators of the correlation of demand indices with quantity-frequency (QF) and severity measures.

DESIGN

Random-effects meta-analyses and meta-regressions involving studies with cross-sectional correlational designs.

SETTING AND PARTICIPANTS

Eleven studies, 10 outcomes and 2146 participants from two countries (USA and UK) published up to 1 October 2018.

MEASUREMENTS

Omnibus effect sizes (correlation coefficients) of five demand indices from the commodity purchase task [intensity (unconstrained consumption), elasticity (price sensitivity), O_max (maximum expenditure), P_max (price at maximum expenditure) and breakpoint (first price of zero consumption)] with QF and severity measures. Meta-regression models tested moderators of effect sizes (i.e. sample age and sex composition, commodity type and number of prices used in the commodity purchase task).

FINDINGS

Significant omnibus effect sizes were observed with QF and severity measures for intensity (r = 0.32/0.28, QF/severity, respectively), elasticity (r = -0.14/-0.18), O_max (r = 0.30/0.29) and breakpoint (r = 0.17/0.22) values. P_max was only significantly associated with severity measures (r = 0.15). The percentage of female participants and number of prices used in the purchase task significantly moderated P_max and breakpoint effect-size estimates in that stronger associations were observed in samples with a greater percentage of women and in studies using tasks with more price points. Commodity type (cannabis versus cocaine) did not significantly moderate associations involving any demand index.

CONCLUSIONS

Behavioral economic demand as measured by the commodity purchase task is consistently correlated with measures of illicit substance use quantity-frequency and severity.

The impact of cocaine and heroin drug history on motivation and cue sensitivity in a rat model of polydrug abuse

RATIONALE

Comorbid use of heroin and cocaine is highly prevalent among drug users and can greatly increase addiction risk. Nonetheless, little is known regarding how a multi-drug history impacts motivation and cue responsivity to individual drugs.

OBJECTIVE

We used behavioral-economic procedures to examine motivation to maintain drug consumption and tests of drug-seeking to drug-associated cues to assess sensitivity to heroin and cocaine-associated cues in rats that had a self-administration history of heroin, cocaine, or both drugs.

RESULTS

Unexpectedly, we found that groups with a polydrug history of heroin and cocaine did not have higher levels of motivation or cue-induced reinstatement of drug-seeking for either cocaine or heroin compared to single drug groups. Nonetheless, we did find drug-specific differences in both economic price and cue sensitivity. Specifically, demand elasticity was lower for cocaine compared to heroin in animals with a single drug history, but not with polydrug groups. In addition, cocaine demand was predictive of the degree of cue-induced reinstatement of drug-seeking for cocaine following extinction, whereas heroin demand was predictive of the degree of reactivity to a heroin-associated cue. Furthermore, although cue reactivity following the initial self-administration phase did not differ across cues and drug history, reactivity to both heroin and cocaine cues was greater during subsequent heroin use compared to cocaine use, and this enhanced reactivity to heroin cues persisted during forced abstinence.

CONCLUSIONS

These results indicate that there is a greater motivation to maintain cocaine consumption, but higher sensitivity to drug-associated cues with a history of heroin use, suggesting that cocaine and heroin may drive continued drug use through different behavioral processes.

Baseline cocaine demand predicts contingency management treatment outcomes for cocaine-use disorder

Cocaine use disorder (CUD) is a significant public health issue. Behavioral interventions such as contingency management (CM) have been demonstrated to be highly effective in promoting cocaine abstinence. However, identifying individual characteristics associated with cocaine relapse may help improve treatment outcomes. Cocaine demand is a behavioral economic measure that shares a scientific foundation with CM. In the current study, we assessed baseline cocaine demand using a hypothetical cocaine purchasing task. Participants (N = 58) consisted of treatment-seeking individuals with CUD. All participants received 1 month of CM treatment for cocaine abstinence, and treatment responders were defined as presenting 6 consecutive cocaine negative urine samples from thrice weekly clinic visits. Demand data were well described by the exponentiated demand model. Indices of demand (intensity of demand [Q₀], elasticity [α]) were significantly associated with recent (last 30 days) cocaine use. Importantly, linear regression revealed that CM treatment nonresponders presented significantly higher Q₀ (p = .025). Subsequent quantile regression analyses examining the relationship between CM treatment response and Q₀ revealed statistically reliable effects of being a nonresponder across 3 of the lower percentiles (i.e., 15, 25, and 30). Overall, these findings provide further support for the utility of exponentiated demand model. To our knowledge, this is the first study to demonstrate an association between baseline demand and contingency management response and systematically extend the findings of prior demand research to a novel drug class, cocaine. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Not all drugs are created equal: impaired future thinking in opiate, but not alcohol, users

Episodic future thinking refers to the ability to travel forward in time to pre-experience an event. Although future thinking has been intimately linked with self and identity, to our knowledge, no prior research has compared episodic future thinking in populations with different substance use disorders. This study investigates whether there are differences in episodic future thinking between these alcohol and opiate users. The study recruited participants who were on the opiate substitution program (n = 31) and individuals who had been diagnosed with alcohol dependence (n = 21) from the Royal Prince Alfred Hospital Drug and Health Services. Healthy controls (n = 23) were recruited via Royal Prince Alfred Hospital databases and the general community. Past and future thinking was measured using four cue words. After each cue word, participants rated their phenomenological experience (e.g. emotion, reliving experience). Results indicated that alcohol-dependent individuals performed significantly higher in episodic future thinking compared to opiate users. These findings indicate that not all substance use disorder groups share similar episodic thinking capabilities. Our results suggest that the self-projection component of rehabilitation programs may have to be tailored to the different episodic construction abilities found in substance use disorder groups.

SSI Receipt and Alcohol and Other Drug use among Former SSI DA&A Beneficiaries

Following termination of the SSI Drug Addiction and Alcoholism (DA&A) program, a nine-site study followed 1,764 randomly selected SSI beneficiaries over two years. This paper examines how loss of SSI affected use of alcohol and illegal drugs. One-third of study respondents reported neither drinking nor using illegal drugs at baseline (just before the end of the program). Nevertheless, use of illegal drugs was 15 times more prevalent among the study sample (44%) than the general population, while use of alcohol was 1.3 times more prevalent (59%), and use of both alcohol and other drugs was significantly greater among those who would lose SSI than those who would retain it. During the follow-up period, prevalence of drinking and use of illegal drugs remained steady, but mean days of use declined for alcohol and illegal drugs other than marijuana. In three separate repeated measures ordinal regression models we examined the net effect of SSI retention on use of alcohol, marijuana and other illegal drugs over time, controlling for demographics, social and health status, and utilization of substance abuse treatment or self-help. Declines in use of alcohol and illegal drugs other than marijuana were similar for those who retained and those who lost SSI benefits, indicating that termination of the program had no effect on levels of substance use. Higher levels of substance use remained significantly and substantially associated with younger age (under 44 years), psychiatric and legal problems, and family or social conflicts, suggesting that subsets of the DA&A population need individualized services beyond income support.

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.

Progress of and Prospects for Hypothetical Purchase Task Questionnaires in Consumer Behavior Analysis and Public Policy

Based on the conceptual, methodological, and analytical framework of operant behavioral economics, hypothetical purchase task (HPT) questionnaires provide a low cost, scalable, and quantitatively rich source of empirical insights on consumer motivation, preferences, and decision-making. Here, we briefly summarize the history of HPT development and validation in clinically oriented research in addiction through to recent work with more conventional consumer goods and services. We discuss several possible novel applications of HPT methods to consumer behavior analysis for business, marketing, and public policy formulation and evaluation, as well as emerging best practices, limitations, and additional directions for future research and development.

Prevalence, correlates and patterns of heroin use among young adults in the United States

INTRODUCTION

The prevalence of heroin use, abuse, and dependence has increased considerably over the past decade. This increase has largely been driven by young adults (18-25years). This study aims to improve the understanding of heroin use among young adults by determining the prevalence, correlates, patterns and attitude of heroin use among young adults in the US.

METHODS

The 2011-2013 National Survey on Drug Use and Health was analyzed. Study population included 55,940 young adults with valid interviews. Self-reported lifetime, past-year and past-month use of heroin were examined. Descriptive statistics and adjusted odds ratios were estimated in accordance with the complex survey design.

RESULTS

Of the respondents, 18.4 per 1000 (95% CI=16.8-20.0) used heroin at some time in their lives, and 7.3 per 1000 (95% CI=6.3-8.3) and 3.3 per 1000 (95% CI=2.6-4.0) used heroin in the past year and past month, respectively. The single most common route of heroin use was by sniffing. Majority of young adults reported using heroin in combination with other substances. Users of non-prescribed opioid pain relievers, cigarette smokers, illicit drug users and those arrested and booked for breaking the law, had higher odds of using heroin during their lifetime, in the past-year and past-month.

CONCLUSION

Fewer than 2% reported ever using heroin, and 82% of those reported no use in the past month. Majority were polysubstance users and sniffed heroin in combination with other routes of use. Comprehensive programs that target young adult heroin users and address important risk factors for heroin use are needed.

The substitutability of cigarettes and food: A behavioral economic comparison in normal weight and overweight or obese smokers

Obesity and cigarette smoking contribute to a multitude of preventable deaths in the United States and eating and smoking behavior may influence each other. The field of behavioral economics integrates principles from psychology and economics and permits systematic examination of how commodities interrelate with one another. Using this framework, the current study evaluated the effects of rising food and cigarette prices on consumption to investigate their substitutability and their relationship to BMI and associated variables. Behavioral economics categorizes commodities as substitutable when the consumption of one increases as a function of a price increase in the other. Smokers (N = 86) completed a 2-part hypothetical task in which money was allocated to purchase cigarettes and fast-food-style reinforcers (e.g., hamburgers, ice cream) at various prices. Results indicated that food and cigarettes were not substitutes for one another (cross-price elasticity coefficients < .20). Food purchases were independent of cigarette price, whereas cigarette purchases decreased as food price rose. Cross-price elasticity coefficients were significantly associated with confidence in one's ability to control weight without smoking (rs = -.23 and .29), but not BMI (rs = .04 and .04) or postcessation weight concerns (rs = -.05 and .12). Perceived ability to manage weight without cigarettes may influence who substitutes food for cigarettes when quitting. In addition, given observed decreases in purchases of both commodities as food prices increased, these findings imply that greater taxation of fast-food-style reinforcers could potentially reduce consumption of these foods and also cigarettes among smokers. (PsycINFO Database Record

Rearing environment differentially modulates cocaine self-administration after opioid pretreatment: A behavioral economic analysis

BACKGROUND

Research has shown that previous experiences during development, especially if stressful, can alter an organism's response to opioids later in life. Given the previous literature on opioid modulation of cocaine self-administration, the current study raised rats in either an enriched condition (EC) or isolated condition (IC) and employed behavioral economics to study the effects of naltrexone and morphine on cocaine self-administration.

METHODS

EC and IC rats were trained to lever press for cocaine using a within-session demand procedure. This procedure measured cocaine consumption under changing cocaine price by decreasing the dose of cocaine earned throughout a session. Rats were able to self-administer cocaine on a FR1; every 10min the cocaine dose was systematically decreased (0.75-0.003mg/kg/infusion cocaine). After reaching stability on this procedure, rats were randomly pretreated with 0, 0.3, 1, or 3mg/kg naltrexone once every 3days, followed by random pretreatments of 0, 0.3, 1, or 3mg/kg morphine once every 3days. Economic demand functions were fit to each rat's cocaine consumption from each pretreatment, and appropriate mathematical parameters were extracted and analyzed.

RESULTS

Naltrexone decreased the essential value of cocaine in IC rats only. However, morphine decreased the essential value of cocaine and the consumption of cocaine at zero price in both EC and IC rats.

CONCLUSION

These results indicate that environmental experiences during development should be considered when determining the efficacy of opioid drugs, especially for the treatment of substance abuse.

Explaining trends in alcohol-related harms in Scotland 1991-2011 (II): policy, social norms, the alcohol market, clinical changes and a synthesis

OBJECTIVE

To provide a basis for evaluating post-2007 alcohol policy in Scotland, this paper tests the extent to which pre-2007 policy, the alcohol market, culture or clinical changes might explain differences in the magnitude and trends in alcohol-related mortality outcomes in Scotland compared to England & Wales (E&W).

STUDY DESIGN

Rapid literature reviews, descriptive analysis of routine data and narrative synthesis.

METHODS

We assessed the impact of pre-2007 Scottish policy and policy in the comparison areas in relation to the literature on effective alcohol policy. Rapid literature reviews were conducted to assess cultural changes and the potential role of substitution effects between alcohol and illicit drugs. The availability of alcohol was assessed by examining the trends in the number of alcohol outlets over time. The impact of clinical changes was assessed in consultation with key informants. The impact of all the identified factors were then summarised and synthesised narratively.

RESULTS

The companion paper showed that part of the rise and fall in alcohol-related mortality in Scotland, and part of the differing trend to E&W, were predicted by a model linking income trends and alcohol-related mortality. Lagged effects from historical deindustrialisation and socio-economic changes exposures also remain plausible from the available data. This paper shows that policy differences or changes prior to 2007 are unlikely to have been important in explaining the trends. There is some evidence that aspects of alcohol culture in Scotland may be different (more concentrated and home drinking) but it seems unlikely that this has been an important driver of the trends or the differences with E&W other than through interaction with changing incomes and lagged socio-economic effects. Substitution effects with illicit drugs and clinical changes are unlikely to have substantially changed alcohol-related harms: however, the increase in alcohol availability across the UK is likely to partly explain the rise in alcohol-related mortality during the 1990s.

CONCLUSIONS

Future policy should ensure that alcohol affordability and availability, as well as socio-economic inequality, are reduced, in order to maintain downward trends in alcohol-related mortality in Scotland.

The price elasticity of demand for heroin: Matched longitudinal and experimental evidence

This paper reports estimates of the price elasticity of demand for heroin based on a newly constructed dataset. The dataset has two matched components concerning the same sample of regular heroin users: longitudinal information about real-world heroin demand (actual price and actual quantity at daily intervals for each heroin user in the sample) and experimental information about laboratory heroin demand (elicited by presenting the same heroin users with scenarios in a laboratory setting). Two empirical strategies are used to estimate the price elasticity of demand for heroin. The first strategy exploits the idiosyncratic variation in the price experienced by a heroin user over time that occurs in markets for illegal drugs. The second strategy exploits the experimentally induced variation in price experienced by a heroin user across experimental scenarios. Both empirical strategies result in the estimate that the conditional price elasticity of demand for heroin is approximately -0.80.

High-frequency drug purity and price series as tools for explaining drug trends and harms in Victoria, Australia

AIMS

Methamphetamine-related harms in Victoria have increased recently in the context of stable or declining use prevalence. We determine how changes in price and purity of methamphetamine compared to other drugs such as heroin may, in part, explain these divergent patterns.

METHODS

Detailed methamphetamine and heroin purchase price data from 2152 participant interviews from the Melbourne Injecting Drug User cohort study were used to generate drug price series for the period January 2009-June 2013. Data on drug purity from 8818 seizures made within Victoria were used to generate drug purity series during the same period. Purity-adjusted price data for methamphetamine and heroin were obtained for the period 2009-13 by combining the two data sets.

RESULTS

While the average purity of heroin seizures remained consistent and low, the average purity of powder and of crystal methamphetamine seizures increased from 12% [95% confidence interval (CI) = 10-14%] to 37% (95% CI = 20-54%) and 21% (95% CI = 18-23%) to 64% (95% CI = 60-68%), respectively. Crystal methamphetamine purity was bimodal, with observations generally less than 20% or greater than 70%. The average unadjusted price per gram for heroin decreased from $374 (95% CI = $367-381) to $294 (95% CI = $280-308), powder methamphetamine did not change significantly from $252 (95% CI = $233-271), and crystal methamphetamine increased substantially from $464 (95% CI = $416-511) in 2009 to $795 (95% CI = $737-853) in 2011. This increase was offset by an even greater increase in purity, meaning the average purity-adjusted price per gram declined. Furthermore, pure prices of both methamphetamine forms were similar, whereas their unadjusted prices were not. The pure price of heroin fluctuated with no ongoing trends.

CONCLUSIONS

Decreases in methamphetamine purity-adjusted price along with the bimodality of crystal methamphetamine purity may account for some of the recent increase in methamphetamine-related harm. For a given amount spent, methamphetamine purchase power has increased and the presence of extreme purity variations may challenge individuals' control of consumption.

Prolonged withdrawal following cocaine self-administration increases resistance to punishment in a cocaine binge

Drug addiction is characterized by compulsive drug-taking behaviors and a high propensity to relapse following drug cessation. Drug craving and seeking can increase during a period of abstinence, but this phenomenon is not observed in drug-induced reinstatement models. To investigate the effect of withdrawal on cocaine relapse, rats were exposed to extended-access cocaine self-administration and subjected to either 1 or 30 d of withdrawal. When tested during 12 h unlimited access to cocaine (binge), the duration of the withdrawal did not influence cocaine intake. However, using a histamine punishment procedure that greatly suppresses drug-taking behavior, we demonstrate that longer periods of abstinence from cocaine induce a greater persistence in responding for drug in the face of negative consequences.

A behavioral economic approach to assessing demand for marijuana

In the United States, marijuana is the most commonly used illicit drug. Its prevalence is growing, particularly among young adults. Behavioral economic indices of the relative reinforcing efficacy (RRE) of substances have been used to examine the appeal of licit (e.g., alcohol) and illicit (e.g., heroin) drugs. The present study is the first to use an experimental, simulated purchasing task to examine the RRE of marijuana. Young-adult (M age = 21.64 years) recreational marijuana users (N = 59) completed a computerized marijuana purchasing task designed to generate demand curves and the related RRE indices (e.g., intensity of demand-purchases at lowest price; Omax-max. spent on marijuana; Pmax-price at which marijuana expenditure is max). Participants "purchased" high-grade marijuana across 16 escalating prices that ranged from $0/free to $160/joint. They also provided 2 weeks of real-time, ecological momentary assessment reports on their marijuana use. The purchasing task generated multiple RRE indices. Consistent with research on other substances, the demand for marijuana was inelastic at lower prices but became elastic at higher prices, suggesting that increases in the price of marijuana could lessen its use. In regression analyses, the intensity of demand, Omax, and Pmax, and elasticity each accounted for significant variance in real-time marijuana use. These results provide support for the validity of a simulated marijuana purchasing task to examine marijuana's reinforcing efficacy. This study highlights the value of applying a behavioral economic framework to young-adult marijuana use and has implications for prevention, treatment, and policies to regulate marijuana use.

Supply-side response to declining heroin purity: fentanyl overdose episode in New Jersey

The inelastic price demand observations characteristic of illegal drug markets have led to the conclusion that the burden of a negative supply shock would be completely reflected to consumers. This paper argues that the increasing availability of prescription opioids may threaten heroin sellers' profit margin and force them to find alternative methods to compensate buyers in the event of a supply shock. We investigate the 2006 fentanyl overdose episode in New Jersey and argue that the introduction of non-pharmaceutical fentanyl, its spatial distribution, and the timing of overdose deaths may have been related to trends in heroin purity. Using medical examiner data, as well as data from the Drug Enforcement Administration, Office of Diversion Control on retail sales of prescription opioids in a negative binomial specification, we show that month-to-month fluctuations in heroin purity have a significant effect on fentanyl-related overdoses, particularly in those areas where prescription opioids are highly available.

Demand curves for hypothetical cocaine in cocaine-dependent individuals

RATIONALE

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Can price get the monkey off our back? A meta-analysis of illicit drug demand

Because of the increased availability of price data over the past 15 years, several studies have estimated the demand for illicit drugs, providing 462 estimates of the price elasticity. Results from estimating several meta-regressions reveal that these price elasticity estimates are influenced by a number of study characteristics. For instance, the price elasticity differs across drugs, with its absolute value being smallest for marijuana, compared with cocaine and heroin. Furthermore, price elasticity estimates are sensitive to whether demand is modeled in the short-run or the long-run, measures of quantity and price, whether or not alcohol and other illicit drugs are included in the specification of demand, and the location of demand. However, a number of other factors, including the functional form of demand, several specification issues, the type of data and method used to estimate demand, and the quality of the publication outlet, have less influence on the price elasticity.

A triadic neurocognitive approach to addiction for clinical interventions

According to the triadic neurocognitive model of addiction to drugs (e.g., cocaine) and non-drugs (e.g., gambling), weakened "willpower" associated with these behaviors is the product of an abnormal functioning in one or more of three key neural and cognitive systems: (1) an amygdala-striatum dependent system mediating automatic, habitual, and salient behaviors; (2) a prefrontal cortex dependent system important for self-regulation and forecasting the future consequences of a behavior; and (3) an insula dependent system for the reception of interoceptive signals and their translation into feeling states (such as urge and craving), which in turn plays a strong influential role in decision-making and impulse control processes related to uncertainty, risk, and reward. The described three-systems account for poor decision-making (i.e., prioritizing short-term consequences of a decisional option) and stimulus-driven actions, thus leading to a more elevated risk for relapse. Finally, this article elaborates on the need for "personalized" clinical model-based interventions targeting interactions between implicit processes, interoceptive signaling, and supervisory function aimed at helping individuals become less governed by immediate situations and automatic pre-potent responses, and more influenced by systems involved in the pursuit of future valued goals.

Analysis of cigarette purchase task instrument data with a left-censored mixed effects model

The drug purchase task is a frequently used instrument for measuring the relative reinforcing efficacy (RRE) of a substance, a central concept in psychopharmacological research. Although a purchase task instrument, such as the cigarette purchase task (CPT), provides a comprehensive and inexpensive way to assess various aspects of a drug's RRE, the application of conventional statistical methods to data generated from such an instrument may not be adequate by simply ignoring or replacing the extra zeros or missing values in the data with arbitrary small consumption values, for example, 0.001. We applied the left-censored mixed effects model to CPT data from a smoking cessation study of college students and demonstrated its superiority over the existing methods with simulation studies. Theoretical implications of the findings, limitations of the proposed method, and future directions of research are also discussed.

The behavioral economics of drug self-administration: a review and new analytical approach for within-session procedures

RATIONALE

Behavioral-economic demand curve analysis offers several useful measures of drug self-administration. Although generation of demand curves previously required multiple days, recent within-session procedures allow curve construction from a single 110-min cocaine self-administration session, making behavioral-economic analyses available to a broad range of self-administration experiments. However, a mathematical approach of curve fitting has not been reported for the within-session threshold procedure.

OBJECTIVES

We review demand curve analysis in drug self-administration experiments and provide a quantitative method for fitting curves to single-session data that incorporates relative stability of brain drug concentration.

METHODS

Sprague-Dawley rats were trained to self-administer cocaine, and then tested with the threshold procedure in which the cocaine dose was sequentially decreased on a fixed ratio-1 schedule. Price points (responses/mg cocaine) outside of relatively stable brain cocaine concentrations were removed before curves were fit. Curve-fit accuracy was determined by the degree of correlation between graphical and calculated parameters for cocaine consumption at low price (Q(0)) and the price at which maximal responding occurred (P(max)).

RESULTS

Removing price points that occurred at relatively unstable brain cocaine concentrations generated precise estimates of Q(0) and resulted in P (max) values with significantly closer agreement with graphical P(max) than conventional methods.

CONCLUSION

The exponential demand equation can be fit to single-session data using the threshold procedure for cocaine self-administration. Removing data points that occur during relatively unstable brain cocaine concentrations resulted in more accurate estimates of demand curve slope than graphical methods, permitting a more comprehensive analysis of drug self-administration via a behavioral-economic framework.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

The effect of drink price and next-day responsibilities on college student drinking: a behavioral economic analysis

More than [3/4] of U.S. college students report a heavy drinking episode (HDE; 5 (for men) and 4 (for women) drinks during an occasion) in the previous 90 days. This pattern of drinking is associated with various risks and social problems for both the heavy drinkers and the larger college community. According to behavioral economics, college student drinking is a contextually bound phenomenon that is impacted by contingencies such as price and competing alternative reinforcers, including next-day responsibilities such as college classes. This study systematically examines the role of these variables by using hypothetical alcohol purchase tasks to analyze alcohol consumption and expenditures among college students who reported recent heavy drinking (N = 207, 53.1% women). The impact of gender and the personality risk factor sensation seeking (SS) were also assessed. Students were asked how many drinks they would purchase and consume across 17 drink prices and 3 next-day responsibility scenarios. Mean levels of hypothetical consumption were highly sensitive to both drink price and next-day responsibility, with the lowest drinking levels associated with high drink prices and a next-day test. Men and participants with greater levels of SS reported more demand overall (greater consumption and expenditures) than women and students with low SS personality. Contrary to our hypotheses women appeared to be less sensitive to increases in price than men. The results suggest that increasing drink prices and morning academic requirements may be useful in preventing heavy drinking among college students.