PSYC 240 Bellevue College Drug and Behavior and Treatment Questions Finish the following problems. some questions should read article to fill out some ques

PSYC 240 Bellevue College Drug and Behavior and Treatment Questions Finish the following problems. some questions should read article to fill out some question. in the last part, using the class data to finish following question. Thank you so much. Answer the following questions
1. What does a delay discounting task measure?
2. How does delay discounting relate to addiction?
3. Read the paper below and answer the following questions:
Robles, E., Huang, B. E., Simpson, P. M., & McMillan, D. E. (2011). Delay discounting,
impulsiveness, and addiction severity in opioid-dependent patients. Journal of substance abuse
treatment, 41(4), 354–362. https://doi.org/10.1016/j.jsat.2011.05.003
https://www.ncbi.nlm.nih.gov/pubmed/21741198
a. What is/are the question(s) asked by the authors of the paper? (what is the
research question, hypothesis, methods, sample, result, discussion)
b. Below is Figure 1 from the Robles et al., paper. Describe the graph using your
own words and explain what it means.
c. Does the paper confirm/reject the idea of people with drug use disorder being
more impulsive? Explain your answer.
4. Based on our class graph, describe the results of the delayed discounting task. (Mean, Ttest)
5. Describe the outcomes of the statistical analyses and what they mean (i.e., what type of
t-tests did we do and their p-values). （in excel）
6. Are the results of our class consistent with the findings in the Robles et al., paper?
Explain your answer.
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Published in final edited form as:
J Subst Abuse Treat. 2011 December ; 41(4): 354–362. doi:10.1016/j.jsat.2011.05.003.
Delay discounting, impulsiveness, and addiction severity in
opioid-dependent patients
Elias Robles, PhD,
Division of Social & Behavioral Sciences, Arizona State University, Glendale, Arizona
B. Emma Huang, PhD,
Commonwealth Scientific and Industrial Research Organisation, St. Lucia, Australia
Pippa M. Simpson, PhD, and
Translational and Biomedical Center, Children’s Research Institute, 8701 Watertown Plank Road,
Milwaukee, Wisconsin
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Donald E. McMillan, PhD
Department of Pharmacology, University of Arkansas for Medical Sciences, Little Rock, Arkansas
Abstract
Individuals who abuse drugs show higher delay discounting (DD) rate and impulsiveness scores
compared to controls; however, it is unclear if DD rate covaries with severity of the addiction, or
if an individual’s discounting rate can be changed by effective substance abuse treatment. This
study compared methadone maintenance patients (MMT; n=30), who had not used illegal drugs
for two years, to drug-using MMT patients (n=30), and controls (n=25) in terms of addiction
severity, DD rate and impulsiveness. Methadone patients abstinent from illegal drugs scored
significantly lower on a number of addiction severity measures than the drug-using methadone
patients. In addition, both groups of MMT patients showed significantly higher rates of DD and
impulsiveness than the control group; however, no differences in DD rate or impulsiveness were
found between the groups of patients. Results suggest that DD rate and impulsiveness may not
covary with indicators of addiction severity in MMT patients.
Keywords
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delay-discounting; impulsiveness; addiction severity; opioids; methadone; maintenance
1. Introduction
Individuals with substance abuse disorders often seem to behave impulsively, choosing
small immediate rewards associated with drug use over ostensibly larger but delayed
rewards such as good health, freedom from incarceration, and good family relations. Delaydiscounting (DD) refers to the loss of subjective value of a reward as a function of delay to
the reward. In general, studies on DD have shown that given an objectively defined reward
(such as money), as delay to the reward increases, the subjective value of the reward
Corresponding author: Elias Robles, Ph.D., Department of Social and Behavioral Sciences, Arizona State University, 4701 West
Thunderbird Road, MC 3051, Glendale, AZ 85306-4908, Phone (602) 543-4515 Fax (602) 543-6004, elias.robles@asu.edu.
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Robles et al.
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decreases (Rachlin and Green, 1972). This appears to be true for the general population and
in addition, a growing number of studies have revealed that substance abusers consistently
exhibit higher delay discounting rates than non-abusing controls (e.g., Bickel et al., 2006;
Kirby et al,. 1999; Madden et al., 1997; Odum and Bauman, 2010; Petry and Cassarella,
1999; Reynolds et al., 2004; Richards et al., 1999; Vuchinich and Simpson, 1998). In light
of these findings, it has been suggested that a better understanding of delay discounting rate
may have important implications for the prevention and treatment of substance abuse.
Studies on discounting by delay originated in the field of operant intertemporal choice
(Ainslie, 1974; 1975; Mazur, 1987; Rachlin and Green, 1972). Mazur (1987) found that
when pigeons are given a choice between smaller amounts of food delivered immediately,
and a larger amount of food delivered after some delay, their choices are best described by
the following hyperbolic model:
(1)
where vd is the current subjective value of a delayed reward (the indifference point), V is the
nominal value of the delayed reward, d is the delay duration, and k is an empirically derived
constant proportional to the degree of DD. Thus, the higher the value of k, the more rapidly
the subjective value of a reward decays as a function of time to its delivery.
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In 1991, Rachlin, Rainieri and Cross demonstrated hyperbolic discounting of hypothetical
cash rewards in humans. In that study, volunteers were asked to choose between a constant
amount of cash ($1,000) to be delivered after some delay (e.g., 1 month), and cash amounts
($1 to $1,000) to be delivered immediately. The subjective value of the delayed amount was
defined as the indifference point (vd), or the point at which an individual switches from
choosing a smaller immediate amount to a larger delayed amount. By repeating the choice
procedure over a range of delay intervals, Rachlin obtained discounting functions that are
best described by hyperbolic models (Killeen, 2009; Mazur, 1987; McKerchar et al., 2008).
Importantly, similar discounting functions have been obtained when real or hypothetical
rewards are used (Johnson and Bickel, 2002; Madden et al., 2003). Estimation of DD rate
has now been extended to various populations of substance users and, to date, there is
overwhelming evidence that users of tobacco, alcohol, opioids, cocaine, and
methamphetamine discount by delay significantly more than matched non-using controls
(for comprehensive reviews see Bickel et al., 2006, Green and Myerson, 2004, Reynolds,
2006, and Yi et al., 2010).
1.1 Delay discounting and severity of the drug problem
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In addition to the observed differences in DD rate between drug users and non users, a
number of studies have found that the magnitude of discounting as a function of delay
covaries with severity of the substance abuse problem. For example, in two studies,
Vuchinich and Simpson (1998) compared light social drinkers with problem drinkers, and
with heavy social drinkers, and found higher rates of delay-discounting in heavy social
drinkers and problem drinkers than in light social drinkers. Bretteville-Jensen (1999)
compared active injecting amphetamine and/or heroin abusers with past abusers of
amphetamine and/or heroin and non using controls, and found that both, active and past
abusers discounted the value of delayed monetary rewards more than the controls; in
addition, their group of active abusers discounted delayed rewards more than past abusers.
Petry (2001) compared active alcoholics with abstinent alcoholics and with control subjects
without a history of alcohol dependence on their rate of discounting of money ($1000 and
$100), and alcohol (150 and 15 bottles of an alcoholic beverage) as a function of delay.
Petry’s study showed that the two groups of alcoholics discounted money at higher rates
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than the control group. In addition, with exception of the $1000 condition, active alcoholics
discounted at a higher rate than the alcohol-abstinent group. In other words, in three out of
four comparisons, the most rapid discounting was observed in active, followed by abstinent
alcoholics, followed by controls. Then, in a study comparing DD rate between controls and
samples of drug users, Kirby and Petry (2004) found that DD rates were increasingly higher
for controls, abstinent heroin users, and active heroin users. Bickel, Odum, and Madden
(1999) compared delay discounting of hypothetical monetary outcomes by current, never,
and ex-smokers of cigarettes. They found that current smokers discounted the value of
delayed money more than did both comparison groups, and that never-and ex-smokers did
not differ in their discounting of money. Taken together, these cross-sectional studies
suggest that DD rate and drug use may be related in one of three ways. DD rate may either
a) change as a function of severity of the substance use, increasing when the drug abuse
problems are more severe and decreasing as a consequence of abstinence, b) be a preexisting
condition predicting the likelihood of drug use and/or recovery from drug use, or c) result
from an interaction of both processes. In addition, it is possible that both, substance use and
DD might be predicted by a third variable such as IQ (Black and Rosen, 2011; de Wit, 2009;
Perry and Carroll, 2008; Robles, 2010).
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In support of the second proposition (b), some prospective studies have shown that
preexisting differences in delay discounting rate may play a defining role in recovery from
substance use. For example, Tucker and collaborators (Tucker et al., 2002; Tucker et al.,
2006; Tucker et al., 2009) using the Alcohol-Savings Discretionary Expenditure (ASDE)
index found that allocation of monetary expenditures to either alcoholic beverages or
savings -which presumably reflects relative preference for immediate vs. delayed rewardspredicted abstinence from alcohol in nontreated problem drinkers at the 2-year follow-up. In
addition, data pooled from three studies using the ASDE index revealed that the index
incrementally predicted future rates of abstinence from alcohol in recently resolved treated
and nontreated problem drinkers (Tucker et al., 2009). Regarding smokers, a number of
studies show that preexisting DD rate can predict abstinence following cessation treatment.
Krishnan-Sarin and collaborators (2007) found that scores on the experiential delay
discounting test (EDT, Reynolds and Schiffbauer, 2004) predicted abstinence from smoking
in adolescents who participated in a cessation program, although scores on Kirby’s delay
discounting measure (Kirby et al., 1999) did not. Recently, MacKillop and Kahler (2009)
found that, among treatment seeking smokers (who were also heavy drinkers), delay
discounting rate predicted the number of days to first relapse to cigarette smoking after
cessation treatment, independently of degree of nicotine dependence. Similarly, Yoon and
collaborators (2007) found that the individual rate of DD predicted postpartum relapse to
cigarette smoking among women who had discontinued smoking during pregnancy.
Importantly, the study also showed that DD rate did not change over time regardless of their
smoking status at 24 weeks postpartum. Finally, a prospective longitudinal study was
recently published on the relationship between baseline DD rate and the probability of
taking up smoking among a large cohort of volunteers followed from 15 to 21 years of age.
In that study, Audrain-McGovern and collaborators (2009) found that degree of DD was
relatively stable when measured repeatedly over 3 years; that higher DD rate at baseline
predicted a heightened probability to take up smoking; and that having taken up smoking did
not affect DD rate. To our knowledge, theirs is the first prospective study clearly showing
DD rate acting as a stable preexisting variable predicting initiation of substance use, rather
than changing as a consequence of it.
On the other hand, some studies have found no differences in DD rate associated with
abstinence. For example, a recent a study that measured discounting rate for marijuana and
hypothetical cash in self-reported current marijuana dependents, former marijuana
dependents, and controls found no significant differences in DD rate between the groups
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(Johnson et al., 2010). Also, Kirby and Petry (2004) compared groups of self-reported 14day abstinent and current users, and found lower DD rate among abstinent opiate abusers
compared with active users, but did not find differences between abstinent alcoholics and
abstinent cocaine users compared to active alcohol and cocaine users. Then, Heil and
collaborators (2006) compared DD rate among cocaine dependent patients who were either
currently using or had maintained abstinence from cocaine for 30 consecutive days, as well
as a group of non-using community controls. Their study showed no differences in
discounting rate between cocaine using and cocaine abstinent subjects although, consistent
with previous studies, both groups showed higher rates of DD than the group of community
controls. Taken together, these studies (Kirby and Petry, 2004; Heil et al., 2006) show, as
Heil points out, that abstinence of up to 30 days from cocaine may not have a sufficient
effect on delay-discounting rate to be detectable, or that abstinence from cocaine or alcohol
for up to 30 days may not be stable enough to be predicted by a higher preexisting DD rate.
1.2 Effects of cognitive skills on delay discounting
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Impulsiveness can be defined as the tendency to act without proper regard for the long-term
consequences of those acts. Properly pondering the long-range consequences of our
behavior, however, requires adequate cognitive skills as well as an environment suitable to
such decision making. It seems fair to assume, therefore, that the lack of cognitive skills and
a favorable environment might lead to errors and impulsive choices. Supporting this view,
some studies have found that IQ scores correlate negatively with DD rate (de Wit et al.
2007; Shamosh and Gray, 2008; Reynolds et al., 2009). A meta-analysis of 24 studies on the
relation between IQ score and DD rate found a significant negative relation between these
variables, independently of the tests used to measure IQ and DD (Shamosh and Gray, 2008).
Moreover, a study by de Wit et al. (2007) with a large sample of healthy adults showed that
both, DD rate and nonplanning impulsiveness, correlated negatively with IQ scores
independently of the subjects’ socioeconomic status and educational attainment. In addition,
it has been reported that deficits in working memory (Bechara and Martin, 2004) and
concentration during assessment of DD (Hinson et al., 2003; Upton et al., 2009) increase
estimates of DD rate. While IQ is a relatively stable measure, to the extent that lower DD
rate might depend on a person’s ability to properly ponder future events, it may be possible
for some individuals to acquire the skills to choose in less impulsive ways. Recent studies
have shown that interventions to enhance memory skills (Bickel et al., 2011) and to improve
money management skills (Black and Rosen, 2011) can decrease estimates of DD rate in
stimulant abusers; in addition, Black and Rosen found the changes in DD to be associated
with a greater likelihood of drug abstinence. Taken together, these studies suggest that
cognitive skills, particularly those involved in planning and decision making may be
important predictors of both delay discounting rate and drug use.
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1.1 Purpose of the study
This study was conducted to assess the effects of prolonged and confirmed abstinence from
illegal drugs on impulsiveness and delay discounting rate. The study compared rate of DD
between methadone maintenance treatment (MMT) patients who had submitted urine
samples free from illicit drugs during 24 or more consecutive months, MMT patients who
continued to use illicit drugs, and a sample of non drug-using community controls matched
on age, sex and race.
2. Materials and Methods
2.1 Participants
Sixty MMT patients attending a university-affiliated substance abuse treatment clinic
participated in the study. Half of the patients (n=30) had continued to use illicit opioids and
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other drugs after at least 4 weeks of treatment. The remaining 30 MMT patients qualified for
the study because according to the clinic’s random urine testing program, they had remained
abstinent from drugs of abuse (opiates, cocaine, amphetamines, benzodiazepines, PCP,
propoxyphene, barbiturates, and THC) continuously for the previous 24 months. Regular
drug testing at the clinic was conducted through a computerized selection of patients at least
once per month. All urinalyses were conducted by a certified commercial laboratory. For all
clinical and research purposes, missing urine samples were considered drug-positive. In
addition to the patients, 26 non drug-using volunteers were recruited and assigned to the
control group. Qualifying candidates were men and women between 18 and 65 years old,
without current diagnosis for mental illness (e.g., schizophrenia) that might affect their
ability to respond to the assessments. Control subjects were recruited through
advertisements posted at various locations in the community. Initial qualification for
participation in the study was determined through a brief telephone interview and, in the
case of consenting MMT patients, through evaluation of their urinalysis records. All
participating volunteers signed a consent form approved by the institution’s review board.
Study participants were compensated with $50 for completion of the assessments.
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Demographic information for the study sample is presented in Table 1. The groups were
similar in age, sex and racial composition. In the table, significant differences between the
groups are identified in the last column by letters (a, b, and c) corresponding to drug using
patients, drug abstinent patients, and controls. On average, control participants completed
more years of education (15.3) than drug-using (12) and drug-abstinent (11) MMT patients.
More control participants were employed full-time (95%) than in both groups of patients
(33.3%). There were no unemployed control participants, while 60% and 67% of the drugusing and drug-abstinent patients, respectively, were unemployed at the time of the study.
Monthly income differed significantly between the drug-using patients and the control
participants only, with controls reporting a higher income. Significantly more patients in
both MMT groups than control participants smoked cigarettes. Significantly more drugusing patients were on probation (17%) than abstinent patients (6%) or control participants
(none). Both groups of MMT patients reported a higher number of life DWI arrests than
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