Paula C. Vincent

Analytical Problems and Suggestions in the Analysis of Behavioral Economic Demand Curves

Behavioral economic demand curves (Hursh, Raslear, Shurtleff, Bauman, & Simmons, 1988) are innovative approaches to characterize the relationships between consumption of a substance and its price. In this article, we investigate common analytical issues in the use of behavioral economic demand curves, which can cause inconsistent interpretations of demand curves, and then we provide methodological suggestions to address those analytical issues. We first demonstrate that log transformation with different added values for handling zeros changes model parameter estimates dramatically. Second, demand curves are often analyzed using an overparameterized model that results in an inefficient use of the available data and a lack of assessment of the variability among individuals. To address these issues, we apply a nonlinear mixed effects model based on multivariate error structures that has not been used previously to analyze behavioral economic demand curves in the literature. We also propose analytical formulas for the relevant standard errors of derived values such as P max, O max, and elasticity. The proposed model stabilizes the derived values regardless of using different added increments and provides substantially smaller standard errors. We illustrate the data analysis procedure using data from a relative reinforcement efficacy study of simulated marijuana purchasing.

Young-Adult Malt Liquor Drinkers: Prediction of Alcohol Problems and Marijuana Use

Malt liquor (ML) is a cheap, high alcohol content beverage that is marketed to appeal to young adults. Findings from the few published studies of ML use suggest that it may be associated with excessive drinking, alcohol problems, and the use of illicit drugs. The authors conducted separate hierarchical multiple regressions to examine the role of ML use and psychosocial variables (e.g., personality, ML motives) in alcohol-related problems and marijuana use. Demographic characteristics served as controls. The sample consisted of 639 (456 men, 183 women) young adults (M = 22.9 years, SD = 4.2) who regularly (> or =40 oz/week) consumed ML. ML use significantly and positively predicted alcohol problems, ML-specific problems, and marijuana use, above and beyond their associations with typical alcohol use. Marijuana was the illicit drug of choice, and 46% reported concurrent use of marijuana and ML. Those who concurrently used ML and marijuana began drinking at a younger age and reported more substance use (particularly marijuana) and more alcohol-related problems than did non-concurrent users. These results suggest that ML use may represent a risk for alcohol problems and marijuana use.

Predicting Post-Treatment-Initiation Alcohol Use among Patients with Severe Mental Illness and Alcohol Use Disorders.

Few investigators studying alcohol abuse among individuals with a severe mental illness (SMI) have examined predictors of posttreatment alcohol outcomes. In the present study, a multivariate approach based on a theoretical model was used to study the relationship between psychosocial factors and post-treatment-initiation alcohol use. Predictors of alcohol use outcomes were examined in 278 individuals diagnosed with a current schizophrenia-spectrum or bipolar disorder and an alcohol use disorder (AUD). At 6-months follow-up, 144 of 228 available participants (63%) had good clinical outcomes. The results of structural equation modeling indicated that type of pretreatment residential setting was directly related to treatment, with participants who lived in supervised settings (41%) reporting significantly more days of treatment (beta = .34, p < .001). In addition, participants with more psychiatric symptoms, as assessed with the Brief Symptom Inventory and Structured Clinical Interview for the Positive and Negative Syndrome Scale, reported significantly fewer treatment days (beta = -.20, p < .001). Number of days that participants attended treatment was indirectly associated with alcohol use outcomes and was mediated by use of alcohol-specific coping skills, such that more frequent use of such skills was associated with less post-treatment-initiation alcohol use (beta = -.34, p < .001). This study emphasizes the favorable prognosis for alcohol outcomes among treated individuals with SMI and AUD and the importance of psychosocial interventions, particularly those that result in better alcohol-specific coping skills.

Effects of exercise on experimentally manipulated craving for cannabis: A preliminary study.

Cannabis is the most commonly used illicit drug in the United States, and craving for cannabis is related to cannabis use. Exercise has been demonstrated to reduce craving for substances. To examine the effects of exercise on cannabis craving, we conducted a 3-week within-subject crossover experiment. Young-adult men (n = 35) and women (n = 11), age 18–25 years (M = 20.76, SD = 1.68), who regularly (≥3 times per week) used cannabis participated in a cue exposure paradigm to stimulate craving. After each of three separate craving inductions, they completed a 10-min bout of exercise that varied in intensity (rest, moderate, vigorous). Craving was assessed before and after the induction, immediately following the exercise, and at three 10-min intervals (total of 30 min). Results of condition-specific, repeated measures analyses of variance showed nonsignificant reductions in immediate postexercise craving for the moderate and vigorous conditions. We used latent growth modeling to examine the trajectory of craving rebound during the 30 min following exercise and explored the effect of baseline weekly cannabis use in predicting craving rebound. Within 30 min postexercise, craving rebounded for both the moderate, F(3, 135) = 9.10, p < .01, and vigorous, F(3, 135) = 3.48, p < .05, conditions. We found that among cannabis users reporting larger quantities of typical weekly cannabis use, craving rebounded more quickly following vigorous than moderate exercise, b = 0.02, SE = 0.02, 95% confidence interval [0.00, 0.06]. The findings suggest that moderate exercise may be useful for reducing craving, particularly among those who use larger quantities of cannabis.

A beverage-specific measure of expectancies for malt liquor: development and initial testing.

Malt liquor (ML) is a unique, high alcohol content beverage marketed to encourage heavy drinking. We developed the Malt Liquor Expectancy Questionnaire (MLEQ), a beverage-specific measure of alcohol expectancies, and examined its association with typical weekly ML use, typical weekly alcohol use, and alcohol problems. Forty positive and 40 negative expectancy items were administered to a sample of 639 young adults who regularly consumed ML. Exploratory and confirmatory factor analyses led to the development of the 30-item MLEQ. The MLEQ consists of two positive (i.e., Social Facilitation and Enjoyment, Enhanced Sexuality) and two negative factors (i.e., Aggression and Negative Consequences; Impairment and Physical Symptoms) that possess good internal consistency, test-retest reliability, and convergent validity. The psychometrically sound MLEQ contributes to the limited research on beverage-specific expectancies and heavy drinking.

Validation of the Revised Problems Assessment for Substance Using Psychiatric Patients

This study assessed the factor structure, internal consistency, test-retest reliability, and construct validity of the Problems Assessment for Substance Using Psychiatric Patients (PASUPP; Carey, Roberts, Kivlahan, Carey, & Neal, 2004) with a sample of 278 men and women seeking outpatient dual-diagnosis treatment. All participants were diagnosed with a current AUD and schizophrenia and/or bipolar disorder. Initial confirmatory factor analysis did not support the 1-factor model for the 50-item measure found by Carey and colleagues. Instead, exploratory factor analysis yielded a shorter (27-item) scale with four distinct, yet related factors (Physical Problems, Aggression, Social and Financial Consequences, and Psychological Problems). The factor-based scales had good internal consistency (α=.77-.81) and 1-week test-retest reliability (r=.67-.73). The revised PASUPP (PASUPP-R) was associated with measures of psychiatric symptoms/adjustment, substance use/dependence, and another measure of substance use problems, providing evidence for convergent validity. Subgroup comparisons suggested few demographic differences on the PASUPP-R, but differential patterns of problems endorsement emerged as a function of mental health and substance use diagnosis. Overall, this study provides preliminary evidence for the psychometric soundness of the PASUPP-R as a measure of problems experienced by persons with co-occurring psychiatric and substance use disorders.