Nehal P. Vadhan

Measures of Attentional Bias and Relational Responding Are Associated with Behavioral Treatment Outcome for Cocaine Dependence

Background: Psychosocial interventions for substance dependence have demonstrated efficacy. However, the mechanisms by which specific intervention strategies exert their effect have not been clearly identified. Objective: This study investigated the prospective relationships between two psychological processes, an attentional bias toward cocaine stimuli and beliefs about the consequences of cocaine use, and treatment outcome. Method: Twenty-five cocaine-dependent participants enrolled in a 6-month outpatient treatment program that included voucher incentives for abstinence. All participants were asked to complete two implicit assessment procedures, a Drug Stroop protocol and an Implicit Relational Assessment Procedure (IRAP), as well as explicit measures of cocaine craving and the consequences of cocaine use, prior to beginning treatment. Pearson’s correlation coefficients tested the prospective relationships between treatment outcome and the implicit and explicit assessments. Results: Stronger implicit beliefs about the positive effects of cocaine use prior to treatment were associated with poorer treatment outcome when an escalating voucher-incentive program was in place. Further, an attentional bias for cocaine-related stimuli was associated with better treatment outcome when an escalating voucher-incentive program was removed. No association between cocaine use beliefs and treatment outcome was found when beliefs were measured with self-report instruments. Conclusions and scientific significance: These findings highlight the potential utility of performance-based measures for delineating the psychological mechanisms associated with variation in response to treatment for drug dependence.

Decision-making in long-term cocaine users: Effects of a cash monetary contingency on Gambling task performance.

BACKGROUND The Iowa Gambling task, which typically incorporates hypothetical monetary earnings and losses for performance, has been widely used to measure decision-making in substance abusers. We examined the effects of a cash monetary contingency on Gambling task performance in cocaine abusers and control participants. METHODS Twenty-two long-term cocaine smokers who met DSM-IV criteria for cocaine dependence and 24 non-cocaine-using control participants completed this study. Both groups were similar in terms of age, executive function, and self-reported alcohol and marijuana use. All participants performed the Gambling task under two counterbalanced conditions: under one condition, earnings and losses were hypothetical, and under the other condition, earnings and losses were in cash. RESULTS Condition x group interactions on card selection and task completion time were noted (p<0.05). Under the hypothetical payment condition, cocaine abusers selected a greater proportion of cards from disadvantageous decks than advantageous decks (p<0.05), but took a similar amount of time to complete the task, relative to control participants. However, under the cash payment condition, no group differences were seen for card selection and cocaine abusers took more time than controls to complete the task (p<0.05). CONCLUSIONS The application of tangible consequences improved the decision-making and effort of cocaine abusers on the Gambling task, relative to control participants. These findings underscore the importance of considering population-specific factors (e.g., sensitivity to instructional vs. consequential control) when conducting neuropsychological research in substance abusers.

Acute effects of smoked marijuana on decision making, as assessed by a modified gambling task, in experienced marijuana users*

The impact of regular marijuana use on executive cognitive abilities, including decision making, is not well understood. While cross-sectional studies have suggested that substance abusers exhibit impaired decision making, as assessed by the Iowa Gambling Task, the direct role of marijuana use in the Gambling Task performance of marijuana smokers has not been well defined. In this report, we present data on performance on a modified Gambling Task in experienced marijuana users after they had smoked marijuana under controlled laboratory conditions. A total of 36 marijuana users, who reported smoking approximately 24 marijuana cigarettes per week, completed this 3-session outpatient study. During each session, these volunteers completed the Gambling Task once at baseline and 3 times after smoking a single marijuana cigarette (0.0, 1.8, or 3.9% Δ9-THC). Marijuana cigarettes were administered in a double-blind fashion, and the sequence of Δ9-THC concentration was balanced across volunteers. Marijuana increased the time required to complete the task. However, advantageous card selection and money earned on the task were not disrupted by marijuana. These data are consistent with previous findings that indicated that speed of performance on tests of executive function, but not accuracy, is disrupted in experienced marijuana users during marijuana intoxication.

Attentional Bias Towards Cocaine-Related Stimuli: Relationship to Treatment-Seeking for Cocaine Dependence

Background: Cocaine-dependent individuals demonstrate attentional bias when measured by Stroop color-naming tasks that have been modified to include cocaine-related words. However, the relationship between attentional bias and the treatment-seeking status of cocaine-dependent individuals has never been explored. The purpose of this study was to compare attentional bias towards cocaine-related verbal stimuli between treatment-seeking and nontreatment-seeking cocaine abusers. Methods: We examined performance on a Stroop task modified to include drug-related words in 17 cocaine-dependent treatment-seeking male participants and 20 cocaine-dependent nontreatment-seeking male participants. Results: Although treatment seekers reported less experience with cocaine than nontreatment seekers, they exhibited increased response latency and made more errors when identifying the colors of cocaine-related words, relative to neutral words (p < .05), whereas nontreatment seekers did not. Conclusions: Factors other than a high frequency of cocaine use may contribute to the difference in attentional bias towards cocaine cues between these subgroups of cocaine users.

Neurocognitive Functioning in Recently Abstinent, Cocaine-Abusing Schizophrenic Patients

PURPOSE This report examined a broad range of cognitive functioning in a group of recently abstinent, cocaine-abusing schizophrenic patients (CA + SZ). METHODS Measures of selective and sustained attention, learning and memory, and executive functioning were administered to CA + SZ patients within 72 h of last cocaine use. A comparison group of non-substance-abusing schizophrenic patients (SZ) presenting for inpatient psychiatric treatment were also examined in an identical time frame. We hypothesized that the neurobiological impact of cocaine abuse and acute abstinence would cause CA + SZ to manifest deficits in all domains of cognitive functioning relative to non-abusing SZ patients. RESULTS Results revealed that CA + SZ displayed significant memory impairment relative to their non-abuser SZ counterparts. No group differences, however, were detected on any other neurocognitive measure. CA + SZ were able to selectively process digit strings during the presence and absence of distracting stimuli, sustain attention, and perform executive functions at performance levels equal to their non-abuser SZ counterparts. IMPLICATIONS These results are consistent with many past studies that have found CA + SZ patients to manifest memory impairment but have relatively well preserved functioning in other cognitive domains. The results are discussed in terms of the biological concomitants of cocaine abuse and acute abstinence in schizophrenia.

A Pilot Study of Neurocognitive Function in Older and Younger Cocaine Abusers and Controls

This pilot study compared basic neurocognitive functioning among older and younger cocaine abusers and control participants, as a preliminary assessment of whether specific cognitive deficits exist in an aged cocaine-abusing population. We hypothesized an interaction between aging and cocaine abuse, such that older cocaine abusers would exhibit decreased neuropsychological test performance relative to both younger cocaine abusers and older control participants. Four groups (n = 20 each) were examined: older cocaine abusers (ages 51-70), younger cocaine abusers (ages 21-39), and two non-illicit substance-using control groups. Basic neuropsychological and psychiatric measures were administered to all participants. Older participants performed more poorly than younger participants on the Mini-Mental State Examination (MMSE, p < .01), Digit Span Backward (p < .01), and Trail Making Test (TMT) Parts A and B (p < .01). Cocaine abusers performed more poorly than controls on TMT A (p < .01). Older and younger cocaine abusers used similar amounts of cocaine (p > .05). Older cocaine abusers performed more poorly than older control participants and younger cocaine abusers on the Digit Span Forward (p < .0125). Older cocaine abusers also performed more poorly than younger cocaine abusers on TMT A (p < .0125). This study provides preliminary evidence that older cocaine abusers use a significant amount of cocaine and that there is an interaction between aging and cocaine abuse on psychomotor speed, attention, and short-term memory. Future examination of neurocognitive function in older cocaine abusers is clearly warranted. 

Reasons for cannabis use among youths at ultra high risk for psychosis

Cannabis use is prevalent in schizophrenia and its risk states, despite its association with anxiety and positive symptoms. While schizophrenia patients report using cannabis for mood enhancement and social motives, it is not known what motivates clinical high risk (CHR) patients to use cannabis.

The effects of heroin administration and drug cues on impulsivity

ABSTRACT Drug addiction is a chronic relapsing disorder characterized by compulsive drug seeking and continued use despite negative consequences. Behavioral impulsivity is a strong predictor of the initiation and maintenance of drug addiction. Preclinical data suggest that heroin may exacerbate impulsive characteristics in an individual but this has yet to be assessed in clinical samples. The current secondary data analysis sought to investigate the effects of heroin on impulsivity along with the effects of exposure to drug cues. Using the current data set, we also tentatively assessed the etiological relationship between impulsivity and heroin abuse. Sixteen heroin-dependent participants were recruited to complete Immediate Memory Task/Delayed Memory Task (IMT/DMT) and GoStop tasks following repeated heroin administration, following acute heroin administration, and following a drug cue exposure session. Four preceding days of active heroin availability, compared to four preceding days of placebo drug availability, increased impulsivity assessed using the IMT and DMT. Presentation of drug cues similarly acted to increase impulsivity assessments on all three tasks. It also appears that heavier users were more susceptible to the influence of drug cues on impulsivity. The present study represents a step toward a more comprehensive understanding of the interaction between opioid abuse and impulsivity. A better understanding of these factors could provide critical insight into the maintenance of heroin use and relapse.

Verbal learning in marijuana users seeking treatment: a comparison between depressed and non-depressed samples

Abstract Background: Both individuals with marijuana use and depressive disorders exhibit verbal learning and memory decrements. Objectives: This study investigated the interaction between marijuana dependence and depression on learning and memory performance. Methods: The California Verbal Learning Test – Second Edition (CVLT-II) was administered to depressed (n = 71) and non-depressed (n = 131) near-daily marijuana users. The severity of depressive symptoms was measured by the self-rated Beck Depression Inventory (BDI-II) and the clinician-rated Hamilton Depression Rating Scale (HAM-D). Multivariate analyses of covariance statistics (MANCOVA) were employed to analyze group differences in cognitive performance. Pearson’s correlation coefficients were calculated to examine the relative associations between marijuana use, depression and CVLT-II performance. Findings from each group were compared to published normative data. Results: Although both groups exhibited decreased CVLT-II performance relative to the test’s normative sample (p < 0.05), marijuana-dependent subjects with a depressive disorder did not perform differently than marijuana-dependent subjects without a depressive disorder (p > 0.05). Further, poorer CVLT-II performance was modestly associated with increased self-reported daily amount of marijuana use (corrected p < 0.002), but was not significantly associated with increased scores on measures of depressive symptoms (corrected p > 0.002). Conclusion: These findings suggest an inverse association between marijuana use and verbal learning function, but not between depression and verbal learning function in regular marijuana users.

Substance Use and Psychosocial Outcomes Following Participation in Residential Laboratory Studies of Marijuana, Methamphetamine and Zolpidem

Rationale: Non-therapeutic research with drugs of abuse in humans is important for a more comprehensive understanding of substance abuse and for the development of more effective treatments. However, the administration of substances from drug classes with abuse potential to human volunteers raises ethical questions regarding potential risk to study volunteers. Objective: The purpose of this study was to assess the psychosocial functioning and reported drug-taking behavior of volunteers before and after participating in a residential laboratory study, during which either marijuana, methamphetamine or zolpidem was administered. Methods: Twenty-two volunteers were administered Addiction Severity Index (ASI) interviews at intake and approximately six months following their study participation. Results: No significant differences between intake and follow-up assessments were found on any ASI composite or drug/alcohol-taking variable. Conclusion: These preliminary data suggest that participation in residential laboratory studies involving the administration of drugs from classes with abuse potential does not alter subsequent psychosocial functioning or reported drug use.