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1.  Personality correlates of pathological gambling derived from Big Three and Big Five personality models 
Psychiatry research  2012;206(1):50-55.
Personality traits have proven to be consistent and important factors in a variety of externalizing behaviors including addiction, aggression, and antisocial behavior. Given the comorbidity of these behaviors with pathological gambling (PG), it is important to test the degree to which PG shares these trait correlates. In a large community sample of regular gamblers (N=354; 111 with diagnoses of pathological gambling), the relations between measures of two major models of personality – Big Three and Big Five – were examined in relation to PG symptoms derived from a semi-structured diagnostic interview. Across measures, traits related to the experience of strong negative emotions were the most consistent correlates of PG, regardless of whether they were analyzed using bivariate or multivariate analyses. In several instances, however, the relations between personality and PG were moderated by demographic variable such as gender, race, and age. It will be important for future empirical work of this nature to pay closer attention to potentially important moderators of these relations.
PMCID: PMC3635075  PMID: 23078872
Five-factor model; DSM-5; Statistical moderation
2.  Egocentric Social Network Analysis of Pathological Gambling 
Addiction (Abingdon, England)  2012;108(3):584-591.
To apply social network analysis (SNA) to investigate whether frequency and severity of gambling problems were associated with different network characteristics among friends, family, and co-workers. is an innovative way to look at relationships among individuals; the current study was the first to our knowledge to apply SNA to gambling behaviors.
Egocentric social network analysis was used to formally characterize the relationships between social network characteristics and gambling pathology.
Laboratory-based questionnaire and interview administration.
Forty frequent gamblers (22 non-pathological gamblers, 18 pathological gamblers) were recruited from the community.
The SNA revealed significant social network compositional differences between the two groups: pathological gamblers (PGs) had more gamblers, smokers, and drinkers in their social networks than did nonpathological gamblers (NPGs). PGs had more individuals in their network with whom they personally gambled, smoked, and drank with than those with who were NPG. Network ties were closer to individuals in their networks who gambled, smoked, and drank more frequently. Associations between gambling severity and structural network characteristics were not significant.
Pathological gambling is associated with compositional but not structural differences in social networks. Pathological gamblers differ from non-pathological gamblers in the number of gamblers, smokers, and drinkers in their social networks. Homophily within the networks also indicates that gamblers tend to be closer with other gamblers. This homophily may serve to reinforce addictive behaviors, and may suggest avenues for future study or intervention.
PMCID: PMC3578111  PMID: 23072641
Pathological gambling; social network analysis; egocentric; alcohol; tobacco
3.  Living in the Here and Now: Interrelationships between Impulsivity, Mindfulness, and Alcohol Misuse 
Psychopharmacology  2011;219(2):10.1007/s00213-011-2573-0.
Impulsivity and mindfulness both emphasize orientation to the present, and both have been linked to alcohol misuse, but the relationship between the two is not clearly understood.
To examine the relationships between elements of impulsivity and mindfulness, and to examine both variables in relation to alcohol misuse.
Young adults (N = 116) were assessed for alcohol use, mindfulness, and impulsivity using psychometrically validated measures.
Numerous significant associations were present among the facets of impulsivity and mindfulness. The variable most substantially associated with alcohol misuse was Negative Urgency (NU; i.e., proneness to act out under conditions of negative affect). After controlling for other variables, Negative Urgency (NU), Positive Urgency (PU), and delay discounting (DD) were significantly related to alcohol consumption. When examining drinking related consequences, only Lack of Premeditation (LoP) and Negative Urgency (NU) were significant associated.
There was considerable overlap between some elements of impulsivity and mindfulness while the overlap was negligible for other facets. The associations between mindfulness and alcohol misuse were entirely a function of impulsivity. In particular, acting on impulses while experiencing negative affect was significantly associated with level of alcohol consumption and level of alcohol-related risk. Steep discounting of future rewards was associated with alcohol consumption while poor premeditation was associated with adverse drinking consequences. These findings illustrate the importance of jointly studying impulsivity when examining purported effects of mindfulness traits.
PMCID: PMC3881594  PMID: 22169883
Alcohol; Impulsivity; Mindfulness; Delay Discounting; Urgency
4.  Integrating Behavioral Economics and Behavioral Genetics: Delayed Reward Discounting as an Endophenotype for Addictive Disorders 
Delayed reward discounting is a behavioral economic index of impulsivity, referring to how much an individual devalues a reward based on its delay in time. As a behavioral process that varies considerably across individuals, delay discounting has been studied extensively as a model for self-control, both in the general population and in clinical samples. There is growing interest in genetic influences on discounting and, in particular, the prospect of discounting as an endophenotype for addictive disorders (i.e., a heritable mechanism partially responsible for conferring genetic risk). This review assembles and critiques the evidence supporting this hypothesis. Via numerous cross-sectional studies and a small number of longitudinal studies, there is considerable evidence that impulsive discounting is associated with addictive behavior and appears to play an etiological role. Moreover, there is increasing evidence from diverse methodologies that impulsive delay discounting is temporally stable, heritable, and that elevated levels are present in nonaffected family members. These findings suggest that impulsive discounting meets the criteria for being considered an endophenotype. In addition, recent findings suggest that genetic variation related to dopamine neurotransmission is significantly associated with variability in discounting preferences. A significant caveat, however, is that the literature is modest in some domains and, in others, not all the findings have been supportive or consistent. In addition, important methodological considerations are necessary in future studies. Taken together, although not definitive, there is accumulating support for the hypothesis of impulsive discounting as an endophenotype for addictive behavior and a need for further systematic investigation.
PMCID: PMC3881595  PMID: 23344986
Delay Discounting; Impulsivity; Behavioral Economics; Genetics; Addiction; Substance Dependence; Review
Addictive behaviors  2012;38(1):1431-1434.
Impulsivity and risk-taking propensity are neurobehavioral traits that reliably distinguish between smoking and non-smoking adults. However, how these traits relate to smoking quantity and nicotine dependence among older adolescent smokers is unclear. The current study examined impulsivity and risk-taking propensity in relation to smoking behavior and nicotine dependence among current older adolescent smokers (age 16–20 years; N = 107). Participants completed the Barratt Impulsiveness Scale–11 (BIS-11), the Balloon Analogue Risk Task (BART), and self-report measures of smoking behavior and nicotine dependence. Results indicated a significant positive relationship between nicotine dependence and the Attention subscale (β =.20, t = 2.07, p <.05) and the Non-planning subscale (β =.19, t=1.92, p<.06) of the BIS-11. Contrary to expectation, the results also indicated a significant negative relationship between performance on the BART and nicotine dependence (β = −.19, t=−2.18, p <.05), such that greater risk-taking propensity was associated with less dependence. These data suggest that impulsivity and risk-taking propensity are related to older adolescent smoking but are separable traits with distinguishable associations to nicotine dependence among adolescents. These findings support the notion that impulsivity is related to heightened nicotine dependence, but suggest the relationship between risk-taking propensity and nicotine dependence is more ambiguous and warrants further investigation.
PMCID: PMC3493878  PMID: 23006247
older adolescent smoking; impulsivity; risk-taking; nicotine dependence
6.  Subjective Response to Alcohol among Alcohol Dependent Individuals: Effects of the Mu-Opioid Receptor (OPRM1) Gene and Alcoholism Severity 
Subjective response to alcohol has been examined as a marker of alcoholism risk. The A118G single nucleotide polymorphism (SNP) of the mu opioid receptor (OPRM1) gene has been previously associated with subjective response to alcohol in heavy drinkers. The present study seeks to extend the literature by examining the effect of OPRM1 genotype on responses to alcohol in a sample of alcohol dependent individuals. A secondary aim of this study is to examine alcoholism severity as a predictor of subjective responses to alcohol.
Non-treatment seeking problem drinkers (n = 295) were assessed in the laboratory for clinical dimensions of alcohol dependence. Following prospective genotyping, 43 alcohol dependent individuals across the two genotype conditions (AA, n = 23 and AG/GG, n = 20) were randomized to two intravenous infusion sessions, one of alcohol (target BrAC = 0.06 g/dl) and one of saline. Measures of subjective responses to alcohol were administered in both infusion sessions.
Alcohol dependent G-allele carriers reported greater alcohol-induced stimulation, vigor, and positive mood, as compared to A-allele homozygotes. There was no genotype effect on alcohol-induced sedation or craving. There was a statistical trend-level severity × alcohol interaction such that individuals at higher levels of severity reported greater alcohol-induced tension reduction.
These results support the hypothesis that OPRM1 genotype moderates the hedonic effects of alcohol, but not the sedative and unpleasant effects of alcohol, in a sample of alcohol dependent patients. Results are discussed in light of a clinical neuroscience framework to alcoholism.
PMCID: PMC3548029  PMID: 23240711
alcohol dependence; responses to alcohol; genetics; OPRM1; A118G SNP; endophenotype
7.  Symptoms of Depression and PTSD are Associated with Elevated Alcohol Demand 
Drug and alcohol dependence  2012;127(0):129-136.
Behavioral economic demand curves measure individual differences in motivation for alcohol and have been associated with problematic patterns of alcohol use, but little is known about the variables that may contribute to elevated demand. Negative visceral states have been theorized to increase demand for alcohol and to contribute to excessive drinking patterns, but little empirical research has evaluated this possibility. The present study tested the hypothesis that symptoms of depression and PTSD would be uniquely associated with elevated alcohol demand even after taking into account differences in typical drinking levels.
An Alcohol Purchase Task (APT) was used to generate a demand curve measure of alcohol reinforcement in a sample of 133 college students (50.4% male, 64.4% Caucasian, 29.5% African-American) who reported at least one heavy drinking episode (5/4 or more drinks in one occasion for a man/woman) in the past month. Participants also completed standard measures of alcohol consumption and symptoms of depression and PTSD.
Regression analyses indicated that symptoms of depression were associated with higher demand intensity (alcohol consumption when price = 0; ΔR2 = .05, p = .002) and lower elasticity (ΔR2 = .04, p = .03), and that PTSD symptoms were associated with all five demand curve metrics (ΔR2 = .04 – .07, ps < .05).
These findings provide support for behavioral economic models of addiction that highlight the role of aversive visceral states in increasing the reward value of alcohol and provide an additional theoretical model to explain the association between negative affect and problematic drinking patterns.
PMCID: PMC3775331  PMID: 22809894
behavioral economics; alcohol abuse; reinforcement; demand curve; comorbidity
8.  High-resolution Behavioral Economic Analysis of Cigarette Demand to Inform Tax Policy 
Addiction (Abingdon, England)  2012;107(12):2191-2200.
Novel methods in behavioral economics permit the systematic assessment of the relationship between cigarette consumption and price. Toward informing tax policy, the goals of this study were to conduct a high-resolution analysis of cigarette demand in a large sample of adult smokers and to use the data to estimate the effects of tax increases in ten U.S. States.
In-person descriptive survey assessment.
Academic departments at three universities.
Adult daily smokers (i.e., 5+ cigarettes/day; 18+ years old; ≥8th grade education); N = 1056.
Estimated cigarette demand, demographics, expired carbon monoxide.
The cigarette demand curve exhibited highly variable levels of price sensitivity, especially in the form of ‘left-digit effects’ (i.e., very high price sensitivity as pack prices transitioned from one whole number to the next; e.g., $5.80-$6/pack). A $1 tax increase in the ten states was projected to reduce the economic burden of smoking by an average of $531M (range: $93.6M-$976.5M) and increase gross tax revenue by an average of 162% (range: 114%- 247%).
Tobacco price sensitivity is nonlinear across the demand curve and in particular for pack-level left-digit price transitions. Tax increases in U.S. states with similar price and tax rates to the sample are projected to result in substantial decreases in smoking-related costs and substantial increases in tax revenues.
PMCID: PMC3504189  PMID: 22845784
Nicotine Dependence; Cigarette Demand; Behavioral Economics; Tax Policy
9.  Behavioral Economic Analysis of Withdrawal- and Cue-Elicited Craving for Tobacco: An Initial Investigation 
Nicotine & Tobacco Research  2012;14(12):1426-1434.
The role of craving in nicotine dependence remains controversial and may be a function of measurement challenges. The current study used behavioral economic approach to test the hypotheses that subjective craving from acute withdrawal and exposure to tobacco cues dynamically increases the relative value of cigarettes.
Using a 2 (1-hr/12-hr deprivation) × 2 (neutral/tobacco cues) within-subjects design, 33 nicotine dependent adults completed 2 laboratory sessions. Assessment included subjective craving and behavioral economic indices of cigarette demand, namely Intensity (i.e., cigarette consumption at zero cost), O max (i.e., maximum total expenditure), Breakpoint (i.e., highest acceptable price for cigarettes), P max (i.e., price at which consumption becomes sensitive to price), and elasticity (i.e., price sensitivity). Behavioral economic indices were generated using a Cigarette Purchase Task in which participants selected between cigarettes for a subsequent 2-hr self-administration period and money.
Main effects of deprivation and tobacco cues were present for subjective craving and multiple behavioral economic indices of cigarette demand. Interestingly, deprivation significantly increased Breakpoint (p ≤ .01) and P max (p ≤ .05) and had trend-level effects on Intensity and O max (p ≤ .10); whereas cues significantly reduced elasticity (p ≤ .01), reflecting lower sensitivity to increasing prices. Heterogeneous associations were evident among the motivational variables but with aggregations suggesting variably overlapping motivational channels.
These findings further support a behavioral economic approach to craving and a multidimensional conception of acute motivation for addictive drugs. Methodological considerations, including potential order effects, and the need for further refinement of these findings are discussed.
PMCID: PMC3509008  PMID: 22416117
10.  Latent factor structure of a behavioral economic cigarette demand curve in adolescent smokers 
Addictive behaviors  2012;37(11):1257-1263.
Behavioral economic demand curves, or quantitative representations of drug consumption across a range of prices, have been used to assess motivation for a variety of drugs. Such curves generate multiple measures of drug demand that are associated with cigarette consumption and nicotine dependence. However, little is known about the relationships among these facets of demand. The aim of the study was to quantify these relationships in adolescent smokers by using exploratory factor analysis to examine the underlying structure of the facets of nicotine incentive value generated from a demand curve measure. Participants were 138 adolescent smokers who completed a hypothetical cigarette purchase task, which assessed estimated cigarette consumption at escalating levels of price/cigarette. Demand curves and five facets of demand were generated from the measure: Elasticity (i.e., 1/α or proportionate price sensitivity); Intensity (i.e., consumption at zero price); Omax (i.e., maximum financial expenditure on cigarettes); Pmax (i.e., price at which expenditure is maximized); and Breakpoint (i.e., the price that suppresses consumption to zero). Principal components analysis was used to examine the latent structure among the variables. The results revealed a two-factor solution, which were interpreted as “Persistence,” reflecting insensitivity to escalating price, and “Amplitude,” reflecting the absolute levels of consumption and price. These findings suggest a two factor structure of nicotine incentive value as measured via a demand curve. If supported, these findings have implications for understanding the relationships among individual demand indices in future behavioral economic studies and may further contribute to understanding of the nature of cigarette reinforcement.
PMCID: PMC3597467  PMID: 22727784
tobacco; smoking; adolescents; behavioral economics; reinforcement; demand curve; nicotine dependence; motivation
11.  Understanding Naltrexone Mechanism of Action and Pharmacogenetics in Asian Americans via Behavioral Economics: A Preliminary Study 
A behavioral economic approach to understanding the relative value of alcohol may be useful for advancing medication development for alcoholism. Naltrexone is a heavily researched and moderately effective treatment for alcohol dependence making it a good candidate for a proof-of-concept study of behavioral economics and alcoholism pharmacotherapy.
This study examines naltrexone efficacy and pharmacogenetics in terms of the relative value of alcohol, assessed via demand curve analysis.
Materials and Methods
Participants were 35 heavy drinking (AUDIT ≥ 8) Asian Americans. A within-subjects cross-over medication design was used along with an intravenous alcohol challenge completed after four days of both naltrexone and placebo. At baseline and BrAC = 0.06 g/dl, participants completed an Alcohol Purchase Task, which assessed estimated alcohol consumption along escalating prices. Behavioral economic demand curve analysis yielded measures of Intensity, Elasticity, maximum expenditure (Omax), proportionate price insensitivity (Pmax) and breakpoint.
Compared to placebo, naltrexone significantly reduced Intensity, Omax and breakpoint. There were also a trend level medication effects on Pmax. BrAC was associated with increases in Pmax and breakpoint. A significant naltrexone × OPRM1 genotype interaction was observed for intensity of demand.
The present study extends the literature on naltrexone’s mechanisms through the application of a novel behavioral economic paradigm. These results indicate that naltrexone reduces several indices of demand for alcohol. This preliminary report provides further evidence for the effectiveness of naltrexone and supports the utility of a behavioral economic approach to alcoholism pharmacotherapy development.
PMCID: PMC3741097  PMID: 22429255
Alcohol; Naltrexone; Behavioral Economics; Asian Americans
12.  Polymorphisms of the µ-opioid receptor and dopamine D4 receptor genes and subjective responses to alcohol in the natural environment 
Journal of abnormal psychology  2010;119(1):115-125.
Polymorphisms of the µ-opioid receptor (OPRM1) and dopamine D4 receptor (DRD4) genes are associated with subjective responses to alcohol and urge to drink under laboratory conditions. This study examines these associations in the natural environment using ecological momentary assessment (EMA). Participants were non-treatment seeking heavy drinkers (n = 112, 52% female, 61% alcohol dependent) who enrolled in a study of naltrexone effects on craving and drinking in the natural environment. Data were culled from five consecutive days of drinking reports prior to medication randomization. Analyses revealed that, after drinking, carriers of the Asp40 allele of the OPRM1 gene reported higher overall levels of vigor and lower levels negative mood, as compared to homozygotes for the Asn40 variant. Carriers of the long allele (i.e., ≥ 7 tandem repeats) of the DRD4 endorsed greater urge to drink than homozygotes for the short allele. Effects of OPRM1 and DRD4 VNTR genotypes appear to be alcohol dose-dependent. Specifically, carriers of the DRD4-L allele reported slight decreases in urge to drink at higher levels of estimated Blood Alcohol Concentration (eBAC) and Asp40 carriers reported decreases in vigor and increases in negative mood as eBAC rose, as compared to carriers of the major allele for each gene. Self-reported vigor and urge to drink were positively associated with alcohol consumption within the same drinking episode. This study extends findings on subjective intoxication, urge to drink, and their genetic bases from controlled laboratory to naturalistic settings.
PMCID: PMC3703617  PMID: 20141248
OPRM1; DRD4; urge to drink; alcohol; EMA
13.  A preliminary pharmacogenetic investigation of adverse events from topiramate in heavy drinkers 
Topiramate, an anticonvulsant medication, is an efficacious treatment for alcohol dependence. To date, little is known about genetic moderators of side effects from topiramate. The objective of this study was to examine three single nucleotide polymorphisms (SNPs) of the glutamate receptor GluR5 gene (GRIK1) as predictors of topiramate-induced side effects in the context of a laboratory study of topiramate. Heavy drinkers (n = 51, 19 females), 75% of whom met criteria for an alcohol use disorder, completed a 5-week dose escalation schedule to a target dose of either 200 or 300 mg, or matched placebo. The combined medication groups were compared to placebo-treated individuals for side effects at target dose. Analyses revealed that a SNP in intron 9 of the GRIK1 gene (rs2832407) was associated with the severity of topiramate-induced side effects and with serum levels of topiramate. Genes underlying glutamatergic neurotransmission, such as the GRIK1 gene, may help predict heterogeneity in topiramate-induced side effects. Future studies in larger samples are needed to more fully establish these preliminary findings.
PMCID: PMC3682424  PMID: 19331489
Higher levels of impulsivity have been implicated in the development of alcohol use disorders. Recent findings suggest that impulsivity is not a unitary construct, highlighted by the diverse ways in which the various measures of impulsivity relate to alcohol use outcomes. This study simultaneously tested the following dimensions of impulsivity as determinants of alcohol use and alcohol problems: risky decision-making, self-reported risk attitudes, response inhibition, and impulsive decision-making.
Participants were a community sample of non-treatment seeking problem drinkers (N = 158). Structural Equation Modeling (SEM) analyses employed behavioral measures of impulsive decision-making (Delay Discounting Task, DDT), response inhibition (Stop Signal Task, SST), and risky decision-making (Balloon Analogue Risk Task, BART), and a self-report measure of risk attitudes (Domain-specific Risk-attitude Scale, DOSPERT), as predictors of alcohol use and of alcohol-related problems in this sample.
The model fit well, accounting for 38% of the variance in alcohol problems, and identified two impulsivity dimensions that significantly loaded onto alcohol outcomes: (1) impulsive decision-making, indexed by the DDT; and (2) risky decision-making, measured by the BART.
The impulsive decision-making dimension of impulsivity, indexed by the DDT, was the strongest predictor of alcohol use and alcohol pathology in this sample of problem drinkers. Unexpectedly, a negative relationship was found between risky decision-making and alcohol problems. The results highlight the importance of considering the distinct facets of impulsivity in order to elucidate their individual and combined effects on alcohol use initiation, escalation, and dependence.
PMCID: PMC3291799  PMID: 22091877
impulsivity; alcohol use; alcohol problems; delayed reward discounting; risk-taking
15.  Temporal Stability of a Cigarette Purchase Task 
Nicotine & Tobacco Research  2011;14(6):761-765.
Cigarette purchase tasks (CPTs) are relatively new behavioral economic assessments that efficiently quantify motivation for tobacco by assessing how much an individual values cigarettes. This is achieved by assessing estimated cigarette consumption at escalating levels of price per cigarette and generating several measures of motivation from the resulting demand curve. The temporal stability of the indices generated from a CPT has not been examined to date and was the focus of the current study.
Participants were 11 moderately heavy smokers from the community who completed CPTs and other measures on 2 occasions 1 week apart. The CPT indices of the relative value of cigarettes were (a) intensity (i.e., consumption under minimal cost), (b) Omax (i.e., maximum expenditure for cigarettes), (c) breakpoint (i.e., first price suppressing consumption to 0), and (d) elasticity (i.e., proportionate price sensitivity).
Demand for cigarettes was initially insensitive to price changes (inelastic) but became increasingly sensitive (elastic) as prices increased. Correlations between the demand indices at both administrations were very high magnitude and statistically significant (rs = .76–.99, ps < .001), and no significant within-subjects differences were present.
These findings provide initial support for the temporal stability of motivation for tobacco as measured by a CPT. Future studies with larger samples and timeframes will be important to verify these findings.
PMCID: PMC3356292  PMID: 22157231
16.  The neuroeconomics of nicotine dependence: A preliminary study of delay discounting of monetary and cigarette rewards in smokers using fMRI 
Psychiatry research  2012;202(1):20-29.
Neuroeconomics integrates behavioral economics and cognitive neuroscience to understand the neurobiological basis for normative and maladaptive decision making. Delay discounting is a behavioral economic index of impulsivity that reflects capacity to delay gratification and has been consistently associated with nicotine dependence. This preliminary study used functional magnetic resonance imaging to examine delay discounting for money and cigarette rewards in 13 nicotine dependent adults. Significant differences between preferences for smaller immediate rewards and larger delayed rewards were evident in a number of regions of interest (ROIs), including the medial prefrontal cortex, anterior insular cortex, middle temporal gyrus, middle frontal gyrus, and cingulate gyrus. Significant differences between money and cigarette rewards were generally lateralized, with cigarette choices associated with left hemisphere activation and money choices associated with right hemisphere activation. Specific ROI differences included the posterior parietal cortex, medial and middle frontal gyrus, ventral striatum, temporoparietal cortex, and angular gyrus. Impulsivity as measured by behavioral choices was significantly associated with both individual ROIs and a combined ROI model. These findings provide initial evidence in support of applying a neuroeconomic approach to understanding nicotine dependence.
PMCID: PMC3530421  PMID: 22633679
Nicotine dependence; smoking; tobacco; behavioral economics; neuroeconomics; delay discounting; impulsivity
17.  Effects of Naltrexone on Cortisol Levels in Heavy Drinkers 
The primary objectives of this study were to: (a) examine the neuroendocrine effects of naltrexone vs. placebo by comparing serum cortisol levels; and (b) test the biobehavioral correlates of naltrexone-induced changes in cortisol. Non-treatment seeking heavy drinkers (n = 37) completed two intravenous alcohol administrations, one after naltrexone (50 mg) and one after placebo. Cortisol levels were measured at baseline and after alcohol intake (BrAC = 0.06 g/dl) on both sessions, as were subjective responses to alcohol. Analyses revealed that naltrexone significantly raised overall cortisol levels compared to placebo. Cortisol levels decreased during alcohol administration and a stronger decrease was observed in the naltrexone condition. Cortisol levels were, in turn, inversely related to some of alcohol’s the reinforcing effects (i.e., alcohol ‘high,’ vigor) and positively associated with some of its unpleasant effects (i.e., sedation and subjective intoxication). These results suggest that naltrexone alters cortisol levels in heavy drinkers and that its effects on subjective responses to alcohol may be related, in part, to naltrexone’s ability to activate the HPA-axis.
PMCID: PMC3660224  PMID: 18824022
naltrexone; alcohol; cortisol; HPA-axis; subjective intoxication
18.  Is Talk ‘Cheap’? An Initial Investigation of the Equivalence of Alcohol Purchase Task Performance for Hypothetical and Actual Rewards 
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.
Forty one heavy-drinking adults (56% male) 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.
Pearson correlations revealed very high correspondence between APT performance for hypothetical and actual alcohol (ps < .001). Estimated consumption on the APT was similarly strongly associated with actual consumption during the self-administration period (r = .87, p <.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.
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.
PMCID: PMC3266442  PMID: 22017303
Alcohol; Behavioral Economics; Purchase Task; Demand; Craving; Cue Reactivity
19.  Delay Discounting, Locus of Control, and Cognitive Impulsiveness Independently Predict Tobacco Dependence Treatment Outcomes in a Highly Dependent, Lower Socioeconomic Group of Smokers 
Tobacco use disproportionately affects lower socioeconomic status (SES) groups. Current explanations as to why lower SES groups respond less robustly to tobacco control efforts and tobacco dependence treatment do not fully account for this disparity. The identification of factors that predict relapse in this population might help to clarify these differences. Good candidates for novel prognostic factors include the constellation of behaviors associated with executive function including self-control/impulsiveness, the propensity to delay reward, and consideration and planning of future events. This study examined the ability of several measures of executive function and other key clinical, psychological, and cognitive factors to predict abstinence for highly dependent lower SES participants enrolled in intensive cognitive-behavioral treatment for tobacco dependence. Consistent with predictions, increased discounting and impulsiveness, an external locus of control as well as greater levels of nicotine dependence, stress, and smoking for negative affect reduction predicted relapse. These findings suggest that these novel factors are clinically relevant in predicting treatment outcomes and suggest new targets for therapeutic assessment and treatment approaches.
PMCID: PMC3567840  PMID: 22494224
20.  Delayed reward discounting and addictive behavior: a meta-analysis 
Psychopharmacology  2011;216(3):305-321.
Delayed reward discounting (DRD) is a behavioral economic index of impulsivity and numerous studies have examined DRD in relation to addictive behavior. To synthesize the findings across the literature, the current review is a meta-analysis of studies comparing DRD between criterion groups exhibiting addictive behavior and control groups.
The meta-analysis sought to characterize the overall patterns of findings, systematic variability by sample and study type, and possible small study (publication) bias.
Literature reviews identified 310 candidate articles from which 46 studies reporting 64 comparisons were identified (total N=56,013).
From the total comparisons identified, a small magnitude effect was evident (d=.15; p<.00001) with very high heterogeneity of effect size. Based on systematic observed differences, large studies assessing DRD with a small number of self-report items were removed and an analysis of 57 comparisons (n=3,329) using equivalent methods and exhibiting acceptable heterogeneity revealed a medium magnitude effect (d=.58; p<.00001). Further analyses revealed significantly larger effect sizes for studies using clinical samples (d=.61) compared with studies using nonclinical samples (d=.45). Indices of small study bias among the various comparisons suggested varying levels of influence by unpublished findings, ranging from minimal to moderate.
These results provide strong evidence of greater DRD in individuals exhibiting addictive behavior in general and particularly in individuals who meet criteria for an addictive disorder. Implications for the assessment of DRD and research priorities are discussed.
PMCID: PMC3201846  PMID: 21373791
Delay discounting; Impulsivity; Addiction; Substance dependence; Alcohol; Tobacco; Nicotine; Stimulant; Opiate; Gambling; Meta-analysis
21.  Consistency of Self-Reported Alcohol Consumption on Randomized and Sequential Alcohol Purchase Tasks 
Behavioral economic demand for addictive substances is commonly assessed via purchase tasks that measure estimated drug consumption at a range of prices. Purchase tasks typically use escalating prices in sequential order, which may influence performance by providing explicit price reference points. This study investigated the consistency of value preferences on two alcohol purchase tasks that used either a randomized or sequential price order (price range: free to $30 per drink) in a sample of 91 young adult monthly drinkers. Randomization of prices significantly reduced relative response consistency (p < 0.01), although absolute consistency was high for both versions (>95%). Self-reported alcohol consumption across prices and indices of demand were highly similar across versions, although a few notable exceptions were found. These results suggest generally high consistency and overlapping performance between randomized and sequential price assessment. Implications for the behavioral economics literature and priorities for future research are discussed.
PMCID: PMC3387580  PMID: 22783209
alcohol; purchase task; demand; behavioral economics; consistency
22.  Factor Structure Validation of the Alcohol Dependence Scale in a Heavy Drinking College Sample 
The prevalence of alcohol use disorders in college students necessitates that adequate measures exist to assess students for abuse and dependence. The Alcohol Dependence Scale (ADS) is a continuous measure of the severity of alcohol involvement found to have a unidimensional factor structure in clinical samples. The latent factor structure of the ADS in college drinkers has not been examined and this study sought to replicate unidimensionality. Heavy college drinkers (N=343) completed the ADS. Performance was examined using confirmatory factor analysis (CFA) and exploratory factor analysis (EFA). The CFA did not support a single factor solution. Follow-up EFA revealed a two factor structure. The first, termed “Acute Excessive Drinking” consisted of relatively commonly endorsed items relating to loss of behavioral control, blackouts, and obsessive/compulsive drinking. The second, termed “Severe Withdrawal Symptoms,” consisted of relatively infrequently endorsed items relating to withdrawal symptoms. The ADS does not appear to have the same factor structure in college and clinical samples, making it inadvisable as a linear measure of alcohol problems within a college population.
PMCID: PMC3207273  PMID: 22058604
Alcohol; Assessment; Factor Structure; College Students
23.  Validity of a Demand Curve Measure of Nicotine Reinforcement with Adolescent Smokers 
Drug and alcohol dependence  2010;113(2-3):207-214.
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, Pmax, and Omax. 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 Omax (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.
PMCID: PMC3025087  PMID: 20832200
tobacco; smoking; adolescents; behavioral economics; reinforcement; demand curve; nicotine dependence; motivation
24.  The Role of Genetics in Nicotine Dependence: Mapping the Pathways from Genome to Syndrome 
Nicotine dependence continues to be a major public health problem worldwide and there is unequivocal evidence that genetics play a substantial role in its etiology. This review provides an overview of the evidence for genetic influences and recent advances in the field. Traditional quantitative genetics studies have revealed nicotine dependence is heritable and molecular genetics studies are providing increasing evidence that the genes responsible for nicotine’s pharmacokinetics and pharmacodynamics are particularly important. Despite considerable progress, a number of significant complexities and challenges remain. These include determining the specificity of genetic influences and clarifying the role of interactive contributions. One promising strategy for addressing these issues is an intermediate phenotype approach that attempts to identify the intervening proximal mechanisms that confer differential genetic risk. Understanding these mechanisms may permit more precision in understanding genetic influences and may also identify novel targets for intervention or prevention.
PMCID: PMC3114454  PMID: 21686075
Nicotine Dependence; Genetics; Smoking; Tobacco; Intermediate Phenotype; Endophenotype
25.  The Dopamine D4 Receptor (DRD4) Gene Exon III Polymorphism, Problematic Alcohol Use, and Novelty Seeking: Direct and Mediated Genetic Effects 
Addiction biology  2008;14(2):238-244.
The present study sought to integrate convergent lines of research on the associations among the dopamine D4 receptor (DRD4) gene, novelty seeking, and drinking behaviors with the overall goal of elucidating genetic influences on problematic drinking in young adulthood. Specifically, this study tested a model in which novelty seeking mediated the relationship between DRD4 VNTR genotype and problematic alcohol use. Participants (N = 90, 40 females) were heavy drinking college students. Analyses using a Structural Equation-Modeling (SEM) framework suggested that the significant direct path between DRD4 VNTR genotype and problematic alcohol use was reduced to a trend level in the context of a model that included novelty seeking as a mediator, thereby suggesting that the effects of DRD4 VNTR genotype on problematic alcohol use among heavy drinking young adults were partially mediated by novelty seeking. Cross-group comparisons indicated that the relationships among the model variables were not significantly different in models for men versus women. These results extend recent findings of the association between this polymorphism of the DRD4 receptor gene, problematic alcohol use, and novelty seeking. These findings may also help elucidate the specific pathways of risk associated with genetic influences on alcohol use and abuse phenotypes.
PMCID: PMC3151559  PMID: 18715282
alcohol; DRD4 VNTR; novelty seeking; genetics; mediation; structural equation modeling

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