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1.  A comparison of delay discounting among substance users with and without suicide attempt history 
Although substance use disorders are associated with overall increased suicide risk, there is considerable variability in suicide risk among substance dependent individuals (SDIs). Impairment in impulse control is common among SDIs and may contribute to vulnerability to suicidal behavior. The present study examined the relation between one specific aspect of impulsivity, delay discounting, and suicide attempt history in a sample of SDIs. An interaction was observed between suicide attempt history and discounting rates across delayed reward size. Specifically, SDIs with no history of attempted suicide, devalued small relative to large delayed rewards. In contrast, SDIs with a history of suicide attempts appeared comparatively indifferent to delayed reward size, discounting both small and large delayed rewards at essentially identical rates. These findings provide evidence that, despite the view that SDIs are characterized by marked difficulties in impulsivity, significant variability nevertheless exists within this group in delay discounting tendencies. Furthermore, these differences provide preliminary evidence that specific aspects of impulsivity may help to identify those most at risk for suicidal behavior in this population. The potential implications of our findings for suicide prevention efforts are discussed.
PMCID: PMC3369019  PMID: 22369220
Delay Discounting; Impulsivity; Substance Use Disorders; Suicide
2.  Performance of Young Adult Cannabis Users on Neurocognitive Measures of Impulsive Behavior and their Relationship to Symptoms of Cannabis Use Disorders 
Recent studies suggest that abstinent cannabis users show deficits on neurocognitive laboratory tasks of impulsive behavior. But results are mixed and less is known on the performance of non-treatment seeking, young adult cannabis users. Importantly, relationships between performance on measures of impulsive behavior and symptoms of cannabis addiction remain relatively unexplored. We compared young adult current cannabis users (CU, n = 65) and non-using controls (NU, n = 65) on several laboratory measures of impulsive behavior, as well as on a measure of episodic memory commonly impacted by cannabis use. The CU group performed more poorly than the NU group on the Hopkins Verbal Learning Test-Revised Total Immediate Recall and Delayed Recall. No significant differences were observed on the measures of impulsive behavior (i.e., Iowa Gambling Task [IGT], Go-Stop Task, Monetary Choice Questionnaire, Balloon Analogue Risk Task). We examined relationships between neurocognitive performance and symptoms of cannabis use disorder symptoms (DSM-IV CUD) among the CU group, which revealed that poorer IGT performance was associated with more symptoms of DSM-IV CUD. Our results show poorer memory performance among young adult cannabis users relative to healthy controls, but no differences on measures of impulsive behavior. However, performance on a specific type of impulsive behavior (i.e., poorer decision-making) was associated with more cannabis use disorder symptoms. These results provide preliminary evidence to suggest that decision-making deficits may be more strongly associated with problems experienced from cannabis use, rather than solely being a consequence of cannabis use, per se.
PMCID: PMC3488122  PMID: 22882144
cannabis; addiction; decision-making; neuropsychology; memory; cognitive effects
3.  Correction: Computational Modeling Reveals Distinct Effects of HIV and History of Drug Use on Decision-Making Processes in Women 
PLoS ONE  2013;8(9):10.1371/annotation/5a8e6fe0-623c-4d17-8781-9a0eadf67a43.
PMCID: PMC3770829  PMID: 24039690
4.  Computational Modeling Reveals Distinct Effects of HIV and History of Drug Use on Decision-Making Processes in Women 
PLoS ONE  2013;8(8):e68962.
Drug users and HIV-seropositive individuals often show deficits in decision-making; however the nature of these deficits is not well understood. Recent studies have employed computational modeling approaches to disentangle the psychological processes involved in decision-making. Although such approaches have been used successfully with a number of clinical groups including drug users, no study to date has used computational modeling to examine the effects of HIV on decision-making. In this study, we use this approach to investigate the effects of HIV and drug use on decision-making processes in women, who remain a relatively understudied population.
Fifty-seven women enrolled in the Women's Interagency HIV Study (WIHS) were classified into one of four groups based on their HIV status and history of crack cocaine and/or heroin drug use (DU): HIV+/DU+ (n = 14); HIV+/DU− (n = 17); HIV−/DU+ (n = 14); and HIV−/DU− (n = 12). We measured decision-making with the Iowa Gambling Task (IGT) and examined behavioral performance and model parameters derived from the best-fitting computational model of the IGT.
Although groups showed similar behavioral performance, HIV and DU exhibited differential relationship to model parameters. Specifically, DU was associated with compromised learning/memory and reduced loss aversion, whereas HIV was associated with reduced loss aversion, but was not related to other model parameters.
Results reveal that HIV and DU have differential associations with distinct decision-making processes in women. This study contributes to a growing line of literature which shows that different psychological processes may underlie similar behavioral performance in various clinical groups and may be associated with distinct functional outcomes.
PMCID: PMC3737214  PMID: 23950880
5.  Neurocognitive performance in drug dependent males and females with PTSD symptoms 
Sex differences in neurobiological mechanisms of substance dependence are well documented but studies of sex differences in associated neurocognitive deficits have produced inconsistent results. PTSD is comorbid with substance dependence and frequently affects neurocognition. Thus, we investigated the effects of sex and PTSD symptoms on sustained attention and inhibition abilities among 126 female and 297 male substance dependent individuals (SDIs) using the Immediate Memory Test (IMT). Females with significant PTSD (PTSD+) symptoms demonstrated significantly impaired IMT performance relative to other participants. These results represent progress in efforts to delineate sex-specific risk factors for neurocognitive deficits among SDIs.
PMCID: PMC3337707  PMID: 22385364
6.  Impact of HIV and a history of marijuana dependence on procedural learning among individuals with a history of substance dependence 
Marijuana (MJ) use and HIV infection are both associated with neurocognitive deficits, yet there is little research to date examining their interactions, specifically how they pertain to procedural learning (PL). We examined a sample of 86 individuals with a history of dependence for multiple substances who underwent a comprehensive evaluation including measures of mental health, substance use history, and three measures of PL: the photoelectric Rotary Pursuit Task (RPT), the Star Mirror Tracing Task (SMT), and the Weather Prediction Task (WPT). We found that a positive HIV serostatus and a history of marijuana dependence were both independently associated with overall poorer performance on the SMT and RPT in this sample of individuals with a history of dependence for multiple substances. Rate of improvement across trial blocks did not differ as a function of HIV serostatus or history of marijuana dependence. Although we found no significant HIV × MJ interaction for any of the PL tasks, we did observe evidence of additive negative effects from HIV and a history of marijuana dependence on overall performance on the SMT and RPT, but not the WPT. The findings suggest that complex motor skills are adversely affected among abstinent polysubstance users with a history of marijuana dependence and that such deficits are compounded by HIV.
PMCID: PMC3633561  PMID: 21480022
HIV; Cannabis; Nondeclarative memory; Striatum; Motor skills
7.  Psychopathic Heroin Addicts are not Uniformly Impaired across Neurocognitive Domains of Impulsivity 
Drug and alcohol dependence  2010;114(2-3):194-200.
Impulsivity is a hallmark characteristic of drug addiction and a prominent feature of externalizing disorders such as psychopathy that are commonly comorbid with drug addiction. In a previous study (Vassileva et al., 2007) we have shown that psychopathic heroin addicts evidence more impulsive decision-making on the Iowa Gambling Task relative to non-psychopathic heroin addicts. The goal of the current study was to investigate whether the observed impulse-control deficits in psychopathic heroin addicts would generalize to other neurocognitive domains of impulsivity, such as delay discounting and behavioral inhibition among a group of relatively “pure” heroin addicts in Bulgaria who participated in our previous study.
We tested 92 currently abstinent male heroin addicts, classified as psychopathic or non-psychopathic based on the Hare Psychopathy Checklist – Revised (PCL-R). We administered two neurocognitive tasks of impulsivity: (1) Delayed Rewards Discounting Task, a measure of temporal discounting of rewards; and (2) Passive Avoidance Learning Task, a measure of behavioral inhibition.
Psychopathic heroin addicts were not impaired relative to non-psychopathic heroin addicts on the Delayed Rewards Discounting Task and the Passive Avoidance Learning Task, on the latter of which they showed better attentional capacity.
These results indicate that psychopathic heroin users are not uniformly impaired across neurocognitive domains of impulsivity. Combined with our previous findings, these results suggest that the presence of psychopathy may exacerbate decision-making deficits in psychopathic heroin addicts, but it may not have significant effect on other neurocognitive domains of impulsivity in this population.
PMCID: PMC3062675  PMID: 21112701
impulsivity; heroin addiction; psychopathy; decision-making; delay discounting; behavioral inhibition
8.  HIV+ Men and Women Show Different Performance Patterns on Procedural Learning Tasks 
The literature suggests that nondeclarative, or nonconscious, learning might be impaired among HIV+ individuals compared with HIV− matched control groups, but these studies have included relatively few women. We administered measures of motor skill and probabilistic learning, tasks with a nondeclarative or procedural learning component that are dependent on integrity of prefrontal-striatal systems, to well-matched groups of 148 men and 65 women with a history of substance dependence that included 45 men and 30 women seropositive for HIV. All participants were abstinent at testing. Compared to HIV− women, HIV+ women performed significantly more poorly on both tasks, but HIV+ men’s performance did not differ significantly compared to HIV− men on either task. These different patterns of performance indicate that features of HIV-associated neurocognitive disorder (HAND) can not always be generalized from men to women. Additional studies are needed to address directly the possibility of sex differences in HIV-associated neurocognitive disorder (HAND) and the possibility that women might be more vulnerable to the effects of HIV and substance dependence on some neurocognitive functions.
PMCID: PMC2990780  PMID: 20694870
HIV; neurocognition; substance use disorders; addiction; sex differences; procedural learning
9.  Influence of Procedural Learning on Iowa Gambling Task Performance Among HIV+ Individuals with History of Substance Dependence 
HIV+ individuals have been shown to demonstrate deficits on the Iowa Gambling Task (IGT), a complex measure of “decision-making.” Little remains known about what other neurocognitive processes may account for variability in IGT performance among HIV+ samples or the role of procedural learning (PL) in IGT performance. A sample of 49 HIV+ individuals with a history of substance use disorders was examined to explore the relationship between IGT performance and three measures of PL: The Rotary Pursuit, Mirror Star Tracing, and Weather Prediction tasks. We found no statistically significant relationships between IGT performance and any of the PL tasks, despite finding significant correlations among the PL tasks. This pattern of results persisted when analyzing IGT performance in various ways (e.g., performance on earlier trial blocks or impairment classifications). Although other nondeclarative processes (e.g., somatic markers) may be important for IGT performance, these findings do not support PL as an important component neurocognitive process for the IGT. Similarly, these results suggest that differences in PL performance does not account for the decision-making deficits or variability in performances observed on the IGT among HIV+ individuals with a history of substance dependence.
PMCID: PMC2809553  PMID: 19939850
HIV; Substance use disorders; Nondeclarative memory; Implicit memory; Decision-making; Basal ganglia; Orbitofrontal cortex; Executive functions
10.  Deficits in complex motor functions, despite no evidence of procedural learning deficits, among HIV+ individuals with history of substance dependence 
Neuropsychology  2008;22(6):776-786.
HIV and drugs of abuse affect common neural systems underlying procedural memory, including the striatum. We compared performance of 48 HIV seropositive (HIV+) and 48 HIV seronegative (HIV−) participants with history of cocaine and/or heroin dependence across multiple Trial Blocks of three procedural learning (PL) tasks: Rotary Pursuit (RPT), Mirror Star Tracing (MST), and Weather Prediction (WPT). Groups were well matched on demographic, psychiatric, and substance use parameters, and all participants were verified abstinent from drugs. Mixed model ANOVAs revealed that the HIV+ group performed more poorly across all tasks, with a significant main effect of HIV serostatus observed on the MST and a trend toward significance obtained for the RPT. No significant differences were observed on the WPT. Both groups demonstrated significant improvements in performance across all three PL tasks. Importantly, no significant Serostatus X Trial Block interactions were observed on any task. Thus, the HIV+ group tended to perform worse than the HIV− group across all trial blocks of PL tasks with motor demands, but showed no differences in their rate of improvement across all tasks. These findings are consistent with HIV-associated deficits in complex motor skills, but not in procedural learning.
PMCID: PMC2630709  PMID: 18999351
HIV; substance use disorders; basal ganglia; procedural memory; nondeclarative memory; neuropsychology
11.  Are all Drug Addicts Impulsive? Effects of Antisociality and Extent of Multidrug Use on Cognitive and Motor Impulsivity 
Addictive behaviors  2007;32(12):3071-3076.
The purpose of this investigation was to examine the influence of antisociality and extent of multidrug use on cognitive and motor impulsivity among substance dependent individuals (SDIs) that used primarily cocaine and/or heroin. One hundred currently abstinent male SDIs participated in the study. Extent of multidrug use and degree of antisociality, assessed with the Socialization Scale of the California Psychological Inventory (So-CPI), were used to classify participants into one of four groups: high antisocial/low multidrug use, high antisocial/high multidrug use, low antisocial/low multidrug use, and low antisocial/high multidrug use. All subjects completed the Iowa Gambling Task to assess cognitive impulsivity and the Stroop Task to measure motor impulsivity. Contrary to expectations, antisociality was associated with more advantageous performance on the Iowa Gambling Task, independent of extent of multidrug use. In contrast, greater multidrug use was associated with general psychomotor slowing on the Stroop Task. Results suggest that a subclinical form of antisociality may have a paradoxically facilitating effect on decision-making and cognitive impulsivity among SDIs.
PMCID: PMC2128047  PMID: 17507173
drug addiction; impulsivity; antisocial; polysubstance use; multidrug use; decision-making
12.  Differential effects of naltrexone on cardiac, subjective and behavioural reactions to acute ethanol intoxication 
Alcohol may have psychomotor stimulant properties during the rising limb of the blood alcohol curve at commonly self-administered doses. Increased heart rate (HR) immediately after alcohol consumption may serve as an indicator or marker of such properties, which appear to be potentially opiate-mediated and dopamine-dependent. Naltrexone, an opiate antagonist, has been used successfully in the treatment of alcoholism and may produce its therapeutic effects through its effects on alcohol metabolism or by blocking alcohol's rewarding effects. We hypothesized that, if naltrexone blocks the psychomotor stimulant properties of ethanol, then it would decrease or eliminate the HR increase associated with acute alcohol intoxication and that this would be independent of any effect on alcohol metabolism.
Twenty male subjects were administered placebo and alcohol (1.0 mL 95% USP ethanol/kg body weight) in a laboratory setting on one day and naltrexone (50 mg) and alcohol on another (counterbalanced). We assessed all subjects for a change in HR and for a subjective and behavioural response from 35 to 170 minutes after drug or alcohol administration.
The placebo and alcohol mix produced a significant mean HR increase from baseline (F1,95 = 46.01, p < 0.0001, Cohen's d = 0.62), while naltrexone and alcohol did not (nonsignificant). The significant effects of naltrexone on blood alcohol level did not account for the effect of naltrexone on alcohol-induced HR change but did account for alterations in subjective and behavioural response to alcohol.
Naltrexone appears to substantially reduce the HR increase that is characteristic of alcohol intoxication. This finding appears to lend moderate support to the notions that, first, naltrexone has differential effects on alcohol reactions and, second, that it specifically blocks the acute psychomotor stimulant properties of alcohol.
PMCID: PMC1635799  PMID: 17136216
alcohol; heart rate; naltrexone; stimulant

Results 1-12 (12)