Restenosis and the proportional neointimal response to coronary artery injury: results in a porcine model

Restenosis is a reparative response to arterial injury occurring with percutaneous coronary revascularization. However, the quantitative characteristics of the relation between vessel injury and the magnitude of restenotic response remain unknown. This study was thus performed to determine the relation between severity of vessel wall injury and the thickness of resulting neointimal proliferation in a porcine model of coronary restenosis. Twenty-six porcine coronary artery segments in 24 pigs were subjected to deep arterial injury with use of overexpanded, percutaneously delivered tantalum wire coils. The vessels were studied microscopically 4 weeks after coil implantation to measure the relation between the extent of injury and the resulting neointimal thickness. For each wire site, a histopathologic score proportional to injury depth and the neointimal thicknesses at that site were determined. Mean injury scores were compared with both mean neointimal thickness and planimetry-derived area percent lumen stenosis. The severity of vessel injury strongly correlated with neointimal thickness and percent diameter stenosis (p less than 0.001). Neointimal proliferation resulting from a given wire was related to injury severity in adjacent wires, suggesting an interaction among effects at injured sites. If the results in this model apply to human coronary arteries, restenosis may depend on the degree of vessel injury sustained during angioplasty.

Long-term outcome in patients undergoing surgical repair of tetralogy of Fallot

BACKGROUND

Although corrective surgery for tetralogy of Fallot has been available for more than 30 years, the occurrence of late sudden death in patients in whom surgery was apparently successful remains worrisome.

METHODS

We studied long-term survival among 163 patients who survived 30 days after complete repair of tetralogy of Fallot, examining follow-up hospital records and death certificates when relevant.

RESULTS

The overall 32-year actuarial survival rate among all patients who survived surgery was 86 percent, as compared with an expected rate of 96 percent in a control population matched for age and sex (P < 0.01). Thirty-year actuarial survival rates were calculated for the patient subgroups. The survival rates among patients less than 5 years old, 5 to 7 years old, and 8 to 11 years old were 90, 93, and 91 percent, respectively--slightly less than the expected rates (P < 0.001, P = 0.06, and P = 0.02). Among patients 12 years old or older at the time of surgery, the survival rate was 76 percent, as compared with an expected rate of 93 percent (P < 0.001). The performance of a palliative Blalock-Taussig shunt procedure before repair, unlike the performance of a Waterston or Potts shunt procedure, was not associated with reduced long-term survival, nor was the need for a trans-annular patch at the time of surgery. Independent predictors of long-term survival were older age at operation (P = 0.02) and a higher ratio of right ventricular to left ventricular systolic pressure after surgery (P = 0.008). Late sudden death from cardiac causes occurred in 10 patients during the 32-year period.

CONCLUSIONS

Among patients with surgically repaired tetralogy of Fallot, the rate of long-term survival after the postoperative period is excellent but remains lower than that in the general population. The risk of late sudden death is small.

Long-term outcome after surgical repair of isolated atrial septal defect. Follow-up at 27 to 32 years

BACKGROUND

Atrial septal defects have been surgically correctable for more than 30 years. The long-term survival rates among patients treated in the early era of cardiac surgery are poorly documented, but such data are of critical importance to the future medical care, employability, and insurability of these patients.

METHODS

To determine the natural history of surgically corrected atrial septal defects, we studied all 123 patients who underwent repair of an isolated defect (ostium secundum or sinus venosus) at the Mayo Clinic between 1956 and 1960, 27 to 32 years after the procedure. The follow-up status of all patients was determined by written questionnaires and telephone interviews. Hospital records and death certificates were obtained if interim hospitalization or death had occurred.

RESULTS

The overall 30-year actuarial survival rate among survivors of the perioperative period was 74 percent, as compared with 85 percent among controls matched for age and sex. The perioperative mortality was 3.3 percent (four deaths). Actuarial 27-year survival rates among patients in the younger two quartiles according to age at operation (less than or equal to 11 years and 12 to 24 years) were no different from rates among controls--97 percent and 93 percent, respectively. In the two older quartiles (25 to 41 years and greater than 41 years), 27-year survival rates were significantly less (P less than 0.001)--84 percent and 40 percent, respectively--than in controls (91 and 59 percent). Independent predictors of long-term survival according to multivariate analysis were age at operation (P less than 0.0001) and systolic pressure in the main pulmonary artery before operation (P less than 0.0027). When repair was performed in older patients, late cardiac failure, stroke, and atrial fibrillation were significantly more frequent.

CONCLUSIONS

Among patients with surgically repaired atrial septal defects, those operated on before the age of 25 have an excellent prognosis, but older patients require careful, regular supervision.

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.

Emboli in infective endocarditis: the prognostic value of echocardiography

OBJECTIVE

To determine whether vegetations visualized on two-dimensional echocardiography are an independent risk factor for the development of subsequent emboli in patients with infective endocarditis and to assess the timing of emboli relative to the initiation of antimicrobial therapy.

DESIGN

Investigator-blinded, retrospective incidence cohort study.

SETTING

Tertiary referral center.

PATIENTS

Patients with left-sided native valve infective endocarditis who had two-dimensional echocardiography within 72 hours of beginning antimicrobial therapy.

MEASUREMENTS AND MAIN RESULTS

The crude incidence rate of first embolic events in patients receiving antimicrobial therapy was 6.2 per 1000 patient-days (95% CI, 4.2 to 9.2). The rates in patients with and without vegetations were 7.1 and 4.9 per 1000 patient-days, respectively (incidence rate ratio, 1.4; 95% CI, 0.6 to 3.3). The relation between vegetations and risk for emboli was microorganism-dependent: Stratified incidence rate ratios were 6.9 (95% CI, 1.1 to 42.5; P less than 0.05) and 1.0 (95% CI, 0.2 to 3.9) for viridans streptococcal and Staphylococcus aureus endocarditis, respectively. The rate of first embolic events diminished over time (P less than 0.001), falling from 13 per 1000 patient-days during the first week of therapy to less than 1.2 per 1000 patient-days after completion of the second week of therapy.

CONCLUSIONS

Overall, the presence of vegetations on echocardiography was not associated with a significantly higher risk for embolus in patients with left-sided native valve infective endocarditis. The relative risk for embolic events associated with echocardiographically visualized vegetations may be microorganism-dependent, with a significantly increased risk seen only in patients with viridans streptococcal infection. The rate of embolic events declines with time after initiation of antimicrobial treatment.

Predictors of alcohol use during the first year of college: implications for prevention

The first year of college is a unique transition period, in which the student establishes a college identity and social network. Alcohol use is often part of this process, and many first-year college students develop a pattern of heavy drinking that puts them at risk for adverse consequences during their college years and into young adulthood. To better understand the development of risky alcohol use during this transition, we reviewed the literature on influences on college drinking and identified moderators and mediators that were particularly relevant for first-year alcohol use. As the transition from high school to college presents a unique opportunity for intervention, we discuss how these moderators and mediators can inform alcohol abuse prevention programs. We also identify approaches aimed at changing the culture of alcohol use on campus. Limitations of the reviewed research are highlighted in the context of promising directions for future research.

Restenosis after balloon angioplasty. A practical proliferative model in porcine coronary arteries

A model of proliferative human restenosis was developed in domestic pigs by using deep injury to the coronary arterial media. Metal wire coils were delivered percutaneously to the coronary arteries of 11 pigs with an oversized, high-pressure (14 atm) balloon and were left in place for times ranging from 28 to 70 days. During placement, the balloon expanded the coils and delivered them securely within the arterial lumen. Light microscopic examination of the vessels confirmed fracture of the internal elastic lamina by the coil. An extensive proliferative response occurred in 10 of the 11 pigs and was associated with a luminal area narrowing of at least 50% in all but one pig. The histopathologic features of the proliferative response were identical to those observed in human cases of restenosis after angioplasty. Immunohistochemical studies confirmed the prominence of smooth muscle cells in the proliferative tissue. A similar response was obtained in two of five porcine coronary arteries in which balloon inflation only was performed, without coil implant. This model is practical and inexpensive and closely mimics the proliferative portion of human restenosis both grossly and microscopically. Thus, it may be useful for understanding human restenosis and for testing therapies aimed at preventing restenosis after balloon angioplasty or other coronary interventional procedures.

Relative reinforcing efficacy of alcohol among college student drinkers

The construct of relative reinforcing efficacy (RRE) is central to many laboratory and theoretical models of drug abuse, but it has not been widely measured in applied clinical research contexts. The authors used a simulated alcohol purchase task to measure RRE in a sample of 267 college student drinkers. Participants reported their alcohol consumption across a range of prices, and their responses were well-described by a regression equation that has been used to construct demand curves in drug self-administration studies. Several measures of relative reinforcing efficacy were generated, including breakpoint, intensity of demand, elasticity, P-sub(max) (price at which response output is maximized), and O-sub(max) (maximum alcohol expenditures). Demand for alcohol was inelastic across the initial range of prices but became elastic as price increased. Students who reported recent heavy drinking reported significantly greater intensity of demand, O-sub(max), and breakpoint. These results provide initial support for the validity of the RRE indices generated with the alcohol purchase task. These results also provide empirical support for programs that attempt to reduce alcohol abuse by eliminating low-cost access to alcohol.

Alcohol demand, delayed reward discounting, and craving in relation to drinking and alcohol use disorders

A behavioral economic approach to alcohol use disorders (AUDs) emphasizes both individual and environmental determinants of alcohol use. The current study examined individual differences in alcohol demand (i.e., motivation for alcohol under escalating conditions of price) and delayed reward discounting (i.e., preference for immediate small rewards compared to delayed larger rewards) in 61 heavy drinkers (62% with an AUD). In addition, based on theoretical accounts that emphasize the role of craving in reward valuation and preferences for immediate rewards, craving for alcohol was also examined in relation to these behavioral economic variables and the alcohol-related variables. Intensity of alcohol demand and delayed reward discounting were significantly associated with AUD symptoms, but not with quantitative measures of alcohol use, and were also moderately correlated with each other. Likewise, craving was significantly associated with AUD symptoms, but not with alcohol use, and was also significantly correlated with both intensity of demand and delayed reward discounting. These findings further emphasize the relevance of behavioral economic indices of motivation to AUDs and the potential importance of craving for alcohol in this relationship.

Further validation of a cigarette purchase task for assessing the relative reinforcing efficacy of nicotine in college smokers

The authors sought to further validate a cigarette purchase task (CPT), a self-report analogue of a progressive-ratio operant schedule, for the assessment of the relative reinforcing efficacy (RRE) of nicotine in smokers. The measure was assessed in terms of its correspondence to typically observed operant behavior, convergent validity, and divergent validity. Participants were 33 individuals (58% male, age M = 19.30 years) who smoked at least weekly (M = 5.31 cigarettes/day) and underwent a single assessment session. Data from the CPT exhibited the predicted inverse relationship between consumption and price, the predicted relationship between consumption and expenditure, and a heterogeneous pattern of interrelationships among the indices of reinforcement. In addition, 2 indices from the measure, intensity of demand and maximum expenditure for cigarettes, exhibited robust convergent and divergent validity. Although this is an incipient research area and the current study used a relatively small sample, these findings support the validity of a CPT as a time- and cost-efficient method for assessing nicotine reinforcement. Theoretical implications of the findings, limitations, and future directions are also discussed.

A randomized controlled trial of a behavioral economic supplement to brief motivational interventions for college drinking

OBJECTIVE

Behavioral economic theory suggests that a reduction in substance use is most likely when there is an increase in rewarding substance-free activities. The goal of this randomized controlled clinical trial was to evaluate the incremental efficacy of a novel behavioral economic supplement (Substance-Free Activity Session [SFAS]) to a standard alcohol brief motivational interviewing (BMI) session for heavy-drinking college students.

METHOD

Participants were 82 first-year college students (50% female; 81.7% White/European American; M age = 18.5 years, SD = 0.71) who reported 2 or more past-month heavy drinking episodes. After completing a baseline assessment and an individual alcohol-focused BMI, participants were randomized to either the SFAS or to a Relaxation Training (RT) control session. The SFAS was delivered in an MI style and attempted to increase the salience of delayed academic and career rewards and the patterns of behavior leading to those rewards.

RESULTS

The combination of an alcohol BMI plus the SFAS was associated with significantly greater reductions in alcohol problems compared with an alcohol BMI plus RT at the 1-month and 6-month follow-up assessments (p = .015, ηp² = .07), an effect that was partially mediated by increases in protective behavioral strategies. BMI + SFAS was also associated with greater reductions in heavy drinking among participants who at baseline reported low levels of substance-free reinforcement or symptoms of depression.

CONCLUSION

These results are consistent with behavioral economic theory and suggest that a single session focused on increasing engagement in alternatives to drinking can enhance the effects of brief alcohol interventions.

Efficacy of counselor vs. computer-delivered intervention with mandated college students

The purpose of this study was to evaluate the efficacy of two brief interventions and the inclusion of a 1-month booster session with college students who were referred to attend alcohol education following an alcohol-related incident. Participants (N=225; 48.9% male) were randomly assigned to receive one session of a Brief Motivational Interview (BMI) or computer-delivered intervention (CDI) with the Alcohol 101 CD-ROM. Participants were also randomly assigned to booster/no booster. At 3-month follow up, participants in BMI reported greater help seeking and use of behavioral strategies to moderate drinking. At 12-month follow up, BMI participants were drinking more frequently and CDI participants were consuming a greater number of drinks per occasion than at baseline. Mediation analyses showed that the use of specific behavioral strategies mediated the effect of the BMI condition on drinking volume. There was no intervention effect on alcohol problems, and the booster condition did not significantly affect outcomes. Promoting specific behaviors in the context of in-person brief interventions may be a promising approach to reducing drinking volume among identified at-risk students.

Is talk "cheap"? An initial investigation of the equivalence of alcohol purchase task performance for hypothetical and actual rewards

BACKGROUND

Behavioral economic alcohol purchase tasks (APTs) are self-report measures of alcohol demand that assess estimated consumption at escalating levels of price. However, the relationship between estimated performance for hypothetical outcomes and choices for actual outcomes has not been determined. The present study examined both the correspondence between choices for hypothetical and actual outcomes, and the correspondence between estimated alcohol consumption and actual drinking behavior. A collateral goal of the study was to examine the effects of alcohol cues on APT performance.

METHODS

Forty-one heavy-drinking adults (56% men) participated in a human laboratory protocol comprising APTs for hypothetical and actual alcohol and money, an alcohol cue reactivity paradigm, an alcohol self-administration period, and a recovery period.

RESULTS

Pearson correlations revealed very high correspondence between APT performance for hypothetical and actual alcohol (ps < 0.001). Estimated consumption on the APT was similarly strongly associated with actual consumption during the self-administration period (r = 0.87, p < 0.001). Exposure to alcohol cues significantly increased subjective craving and arousal and had a trend-level effect on intensity of demand, in spite of notable ceiling effects. Associations among motivational indices were highly variable, suggesting multidimensionality.

CONCLUSIONS

These results suggest there may be close correspondence both between value preferences for hypothetical alcohol and actual alcohol, and between estimated consumption and actual consumption. Methodological considerations and priorities for future studies are discussed.

A behavioral economic measure of demand for alcohol predicts brief intervention outcomes

Considerable basic and clinical research supports a behavioral economic conceptualization of alcohol and drug dependence. One behavioral economic approach to assess motivation for a drug is the use of demand curves, or quantitative representations of drug consumption and drug-reinforced responding across a range of prices. This study used a hypothetical alcohol purchase task to generate demand curves, and examined whether the resulting demand curve parameters predicted drinking outcomes following a brief intervention. Participants were 51 college student drinkers (67% female; 94% Caucasian; drinks/week: M=24.57, S.D.=8.77) who completed a brief alcohol intervention. Consistent with predictions, a number of demand curve indices significantly predicted post-intervention alcohol use and frequency of heavy drinking episodes, even after controlling for baseline drinking and other pertinent covariates. Most prominently, O(max) (i.e., maximum alcohol expenditure) and breakpoint (i.e., sensitivity of consumption to increasing price) predicted greater drinking at 6-month post-intervention follow-up. These results indicate that a behavioral economic measure of alcohol demand may have utility in characterizing the malleability of alcohol consumption. Moreover, these results support the utility of translating experimental assays of reinforcement into clinical research.

Reliability and validity of a demand curve measure of alcohol reinforcement

Recent clinical research suggests that several self-report behavioral economic measures of relative reinforcing efficacy (RRE) may show utility as indices of substance abuse problem severity. The goal of the present study was to evaluate the reliability and validity of the Alcohol Purchase Task (APT), a RRE measure that uses hypothetical choices regarding alcohol purchases at varying prices (demand curves) to generate several indices of alcohol-related reinforcement. Participants were 38 college students who reported recent alcohol consumption. Both the raw alcohol purchase/consumption values and several of the computed reinforcement parameters (intensity & Omax) showed good to excellent 2-week test-retest reliability. Reinforcement parameters derived from both a linear-elasticity (Hursh, Raslear, Bauman, & Black, 1989) and an exponential (Hursh & Silberberg, 2008) demand curve equation were generally less reliable, despite the fact that both equations provided a good fit to participants' reported consumption data. The APT measures of demand intensity (number of drinks consumed when price = 0), Omax (maximum expenditure), and elasticity (alpha) were correlated with weekly drinking, alcohol-related problems, and other self-report RRE measures (relative discretionary monetary expenditures toward alcohol and/or relative substance-related activity participation and enjoyment). Demand intensity was uniquely associated with problem drinking in a regression model that controlled for weekly consumption. These results provide support for the reliability and validity of the RRE indices generated with the APT.

A new pressure ulcer risk assessment scale for individuals with spinal cord injury

Each year, one-fourth of the 200,000 individuals with spinal cord injury in the United States develop pressure ulcers. No method currently exists, however, to accurately identify which of these individuals are at increased risk for development of pressure ulcers. We studied 219 spinal cord-injured patients, seen at a Veterans Affairs Medical Center, during a 6-yr period. Our goal was to develop a pressure ulcer risk assessment scale, specifically for persons with SCI. Each risk factor had to meet four criteria: (1) statistical association with pressure ulcer development; (2) biologically plausible mechanism; (3) literature support; (4) improved prediction. Among the 219 spinal cord-injured patients evaluated, 176 (80.4 percent) had a history of one or more pressure ulcers. Fifteen risk factors met the four criteria for inclusion into the risk assessment scale. They were as follows: restricted activity level, degree of immobility, complete spinal cord injury, urinary disease, impaired cognitive function, diabetes, cigarette smoking, residence in a nursing home or hospital, hypoalbuminemia, and anemia. Compared with the more general scales available, for quantifying the risk of pressure ulcer development, preliminary results suggest that this new scale is a significant improvement for the spinal cord-disabled.

Blood transfusion increases the risk of infection after trauma

To determine whether blood transfusion influences infection after trauma, we analyzed data on 5366 consecutive patients hospitalized for more than 2 days at eight hospitals over a 2-year period. The incidence of infection was significantly related to the mechanism of injury: penetrating injuries, 8.9%; blunt injuries, 12.9%; and low falls, 21.4%. Stepwise logistic regression analyses of infection using the variables age, sex, respiration rate in the emergency department, Glasgow Coma Scale in the emergency department, Injury Severity Score, shock (systolic blood pressure < 90 mm Hg on admission to the emergency department), and log of total amount of blood transfused during hospitalization showed that amount of blood received and Injury Severity Score were the only two variables that were significant predictors of infection across groups. Even when patients were stratified by Injury Severity Score, the infection rate increased significantly with increases in numbers of units of blood. Blood transfusion in the injured patients is an important independent statistical predictor of infection. Its contribution cannot be attributed to age, sex, or the underlying mechanism of severity of injury.

Changes in alcohol use during COVID-19 and associations with contextual and individual difference variables: A systematic review and meta-analysis

OBJECTIVE

The present study meta-analyzed studies examining changes in alcohol consumption during the coronavirus disease (COVID-19) pandemic and systematically reviewed contextual and individual difference factors related to these changes.

METHOD

Following the preferred reporting items for systematic reviews and meta-analysis (PRISMA) protocol, studies were gathered via PsycINFO, PubMed/MEDLINE, and preprint databases (published April 29, 2021) that examined individual-level changes in consumption during the initial COVID-19 mitigation measures (before October 2020). Next, sample proportion increases and decreases in consumption, in addition to mean change in consumption variables from pre- to during-COVID, were meta-analyzed, and contextual and individual difference variables related to consumption changes during the pandemic were summarized.

RESULTS

One hundred and twenty-eight studies provided data from 58 countries (M n = 3,876; Mdn n = 1,092; aggregate sample n = 492,235). The average mean change in alcohol consumption was nonsignificant (Cohen's d = -0.01, p = .68); however, meta-analysis revealed that 23% of participants reported increases in consumption and 23% reported decreases. These changes were moderated by per capita gross domestic product and country. Narrative synthesis revealed multiple predictors of increased drinking, including contextual changes (e.g., children at home, income loss, working remotely), individual difference variables (being female, a young-to-middle aged adult, or Black), and mental health/alcohol-related risk factors (e.g., depression).

CONCLUSIONS

The identified factors associated with increased alcohol consumption should be considered in planning behavioral health services during future crisis events that abruptly alter everyday environments in ways that increase stress and decrease access to naturally occurring rewards. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Relative efficacy of a brief motivational intervention for college student drinkers

The authors evaluated the efficacy of Brief Alcohol Screening and Intervention for College Students (BASICS - L. A. Dimeff, J. S. Baer, D. R. Kivlahan, & G. A. Marlatt, 1999), a single session of drinking-related feedback intended to reduce heavy drinking and related harm. College student drinkers (N = 99) were assigned to BASICS, an educational intervention, or an assessment-only control group. At 3 months postintervention. there were no overall significant group differences, but heavier drinking BASICS participants showed greater reductions in weekly alcohol consumption and binge drinking than did heavier drinking control and education participants. At 9 months, heavier drinking BASICS participants again showed the largest effect sizes. BASICS participants evaluated the intervention more favorably than did education participants. This study suggests that BASICS may be more efficacious than educational interventions for heavier drinking college students.

A comparison of personalized feedback for college student drinkers delivered with and without a motivational interview

OBJECTIVE

This study evaluated the relative efficacy of personalized drinking feedback (PDF) delivered with and without a motivational interview (MI) for college student drinkers.

METHOD

Heavy-drinking college students (N = 54; 691% female) were identified from a large screening sample and randomly assigned either to receive PDF during a single MI session or to receive PDF without an MI. Of these participants, 51 (94%) completed a 6-month follow-up assessment that included measures of alcohol consumption and alcohol-related problems.

RESULTS

At 6-months postintervention, participants in both groups showed significant, small to moderate reductions in alcohol consumption, but the groups did not differ. Women showed larger reductions than men. Rates of alcohol-related problems remained relatively unchanged.

CONCLUSIONS

The hypothesis that an MI would enhance the efficacy of PDF was not supported.

Associations between depression, distress tolerance, delay discounting, and alcohol-related problems in European American and African American college students

Although levels of heavy drinking and alcohol-related problems are high in college students, there is significant variability in the number and type of problems experienced, even among students who drink heavily. African American students drink less and experience fewer alcohol-related problems than European American students, but are still at risk, and little research has investigated the potentially unique patterns and predictors of problems among these students. Depression, distress tolerance, and delay discounting have been implicated in adult substance abuse and may be important predictors of alcohol problem severity among college students. We examined the relationship between these variables and alcohol-related problems among African American and European American students (N = 206; 53% female; 68% European American; 28% African American) who reported recent heavy drinking. In regression models that controlled for drinking level, depression, distress tolerance, and delay discounting were associated with alcohol problems among African American students, but only depression was associated with alcohol problems among European American students. These results suggest that negative affect is a key risk factor for alcohol problems among college student drinkers. For African American students, the inability to tolerate negative emotions and to organize their behavior around future outcomes may also be especially relevant risk factors.

Latent structure of facets of alcohol reinforcement from a behavioral economic demand curve

RATIONALE

Behavioral economic demand curves are quantitative representations of the relationship between consumption of a drug and its cost. Demand curves provide a multidimensional assessment of reinforcement, but the relationships among the various indices of reinforcement have been largely unstudied.

OBJECTIVES

The objective of the study is to use exploratory factor analysis to examine the underlying factor structure of the facets of alcohol reinforcement generated from an alcohol demand curve.

MATERIALS AND METHODS

Participants were 267 weekly drinkers [76% female; age M = 20.11 (SD = .1.51); drinks/week M = 14.33 (SD = 11.82)] who underwent a single group assessment session. Alcohol demand curves were generated via an alcohol purchase task, which assessed consumption at 14 levels of prices from $0 to $9. Five facets of demand were generated from the measure [intensity, elasticity, P (max) (maximum inelastic price), O (max) (maximum alcohol expenditure), and breakpoint], using both observed and derived calculations. Principal components analysis was used to examine the latent structure among the variables.

RESULTS

The results revealed a clear two-factor solution, which were interpreted as "Persistence," reflecting sensitivity to escalating price, and "Amplitude," reflecting the amount consumed and spent. The two factors were generally quantitatively distinct, although O (max) loaded on both.

CONCLUSIONS

These findings suggest that alcohol reinforcement as measured via a demand curve is binary in nature, with separate dimensions of price-sensitivity and volumetric consumption. If supported, these findings may contribute theoretically and experimentally to a reinforcement-based approach to alcohol use and misuse.

Validity of a demand curve measure of nicotine reinforcement with adolescent smokers

High or inelastic demand for drugs is central to many laboratory and theoretical models of drug abuse, but it has not been widely measured with human substance abusers. The authors used a simulated cigarette purchase task to generate a demand curve measure of nicotine reinforcement in a sample of 138 adolescent smokers. Participants reported the number of cigarettes they would purchase and smoke in a hypothetical day across a range of prices, and their responses were well-described by a regression equation that has been used to construct demand curves in drug self-administration studies. Several demand curve measures were generated, including breakpoint, intensity, elasticity, P(max), and O(max). Although simulated cigarette smoking was price sensitive, smoking levels were high (8+ cigarettes/day) at prices up to 50¢ per cigarette, and the majority of the sample reported that they would purchase at least 1 cigarette at prices as high as $2.50 per cigarette. Higher scores on the demand indices O(max) (maximum cigarette purchase expenditure), intensity (reported smoking level when cigarettes were free), and breakpoint (the first price to completely suppress consumption), and lower elasticity (sensitivity of cigarette consumption to increases in cost), were associated with greater levels of naturalistic smoking and nicotine dependence. Greater demand intensity was associated with lower motivation to change smoking. These results provide initial support for the validity of a self-report cigarette purchase task as a measure of economic demand for nicotine with adolescent smokers.

Continuous objective monitoring of alcohol use: twenty-first century measurement using transdermal sensors

Transdermal alcohol sensors continuously collect reliable and valid data on alcohol consumption in vivo over the course of hours to weeks. Transdermal alcohol readings are highly correlated with breath alcohol measurements, but transdermal alcohol levels lag behind breath alcohol levels by one or more hours owing to the longer time required for alcohol to be expelled through perspiration. By providing objective information about alcohol consumption, transdermal alcohol sensors can validate self-report and provide important information not previously available. In this article, we describe the development and evaluation of currently available transdermal alcohol sensors, present the strengths and limitations of the technology, and give examples of recent research using the sensors.