The role of impulsivity in the aetiology of drug dependence: reward sensitivity versus automaticity

The Link Between Cannabis Use and Violent Behavior in the Early Phase of Psychosis: The Potential Role of Impulsivity

INTRODUCTION

Recently, the literature has shown that Cannabis Use (CU) was a risk factor for Violent Behavior (VB) in patients with psychosis, and those in the early phase of psychosis (EPP). These findings are relevant because of the high prevalence of CU in this EPP, and the potential for prevention during this phase of illness. However, there is still a lack of clear explanations, supported by empirical evidence, about what underlies the link between CU and VB against other.

METHOD

This viewpoint reviews the scientific literature on the link between CU and VB, and the involvement of impulsivity in this relationship. This last point will be addressed at clinical and neurobiological levels.

RESULTS

Recent studies confirmed that CU is particularly high in the EPP, and is a risk factor for VB in the EPP and schizophrenia. Studies have also shown that impulsivity is a risk factor for VB in psychosis, is associated with CU, and may mediate the link between CU and VB. Research suggests a neurobiological mechanism, as CU affects the structures and function of frontal areas, known to play a role in impulsive behavior.

CONCLUSION

Scientific evidence support the hypothesis of an involvement of impulsivity as a variable that could mediate the link between CU and aggression, particularly, when CU has an early onset. However, this hypothesis should be confirmed with longitudinal studies and by taking into account confounding factors. The studies highlight the relevance of early prevention in the EPP, in addition to interventions focusing on psychotic disorders.

Association between adult ADHD, self-report, and behavioral measures of impulsivity and treatment outcome in cocaine use disorder

A large and growing body of literature supports the association between cocaine addiction and impulsivity. The aim of the study was to test whether pretreatment screening for adult ADHD, and self-report and behavioral measures of impulsivity have prognostic utility in clinical practice with cocaine users. We enrolled a cohort of N = 86 treatment-seeking cocaine users, assisted by a public addiction service, in a 24 week study. At baseline, we performed screening for adult ADHD, assessed the presence of co-occurring mental disorders, and applied measures of drug use severity, trait-like impulsivity (Barratt Impulsiveness Scale; BIS-11), decision-making (Iowa Gambling Task; IGT), risk-taking (Balloon Analogue Risk Task; BART), and ability to inhibit cognitive interference (Stroop Color Word Test; SCWT). Patients positive to the screening for ADHD showed a higher level of self-reported impulsivity and a longer history of drug use, but did not differ from those without ADHD in adherence to psychosocial treatments and number of negative urines for cocaine during the 24 weeks. Among all of the self-report and behavioral measures used, only IGT BIS-11 was associated with cocaine abstention. The small effect size and the problematic direction of the associations found do not give strong support to the routine use of self-regulation measures to guide clinical decisions in public addiction treatment settings.

Relative expected value of drugs versus competing rewards underpins vulnerability to and recovery from addiction

Behavioural economic theories of addiction contend that greater expected value of drug relative to alternative non-drug rewards is the core mechanism underpinning vulnerability to and recovery from addiction. To evaluate this claim, we exhaustively review studies with human drug users that have measured concurrent choice between drugs vs. alternative rewards, and explored individual differences. These studies show that drug choice can be modulated by drug cues, drug devaluation, imposition of costs/punishment and negative mood induction. Regarding individual differences, dependence severity was reliably associated with overall drug preference, and self-reported drug use to cope with negative affect was reliably associated with greater sensitivity to mood induced increases in drug choice. By contrast, there were no reliable individual differences in sensitivity to the effect of drug cues, drug devaluation or punishment on drug choice. These findings provide insight into the mechanisms that underpin vulnerability to dependence: vulnerability is conferred by greater relative value ascribed to drugs, and relative drug value is further augmented by negative affective states in those who report drug use coping motives. However, dependence does not appear to be characterised by abnormal cue-reactivity, habit learning or compulsion. We then briefly review emerging literature which demonstrates that therapeutic interventions and recovery from addiction might be attributed to changes in the expected relative value of drug versus alternative rewards. Finally, we outline a speculative computational account of the distortions in decision-making that precede action selection in addiction, and we explain how this account provides a blueprint for future research on the determinants of drug choice, and mechanisms of treatment and recovery from addiction. We conclude that a unified economic decision-making account of addiction has great promise in reconciling diverse addiction theories, and neuropsychological evaluation of the underlying decision mechanisms is a fruitful area for future research and treatment.

Higher impulsivity and lower grey matter volume in the bilateral prefrontal cortex in long-term abstinent individuals with severe methamphetamine use disorder

BACKGROUND

Previous studies have shown that grey matter volume (GMV) might be lower in individuals with methamphetamine use disorder and that dynamic alterations in selected brain regions might appear in individuals after short-term abstinence. However, the GMV of brains in these individuals after long-term abstinence is poorly understood. Moreover, individuals with severe methamphetamine use disorder have been considered to have high levels of impulsivity, but the biological mechanism is still unclear.

METHODS

In this study, the impulsivity of all participants was assessed using the Barratt Impulsiveness Scale (BIS-11). Using voxel-based morphometry (VBM) in conjunction with statistical parametric mapping on structural magnetic resonance images, the GMVs of the whole brain were compared among 32 drug-naïve healthy controls (HC) and 40 individuals with severe methamphetamine use disorder who had been abstinent for at least 20 months (SMUD-A).

RESULTS

We observed significantly higher BIS-11 impulsivity scores and lower GMV in the bilateral superior frontal cortex of SMUD-A individuals than in those of control subjects. The impulsivity score was negatively correlated with GMV in the right superior frontal cortex.

CONCLUSIONS

These findings offer novel evidence with respect to the impulsivity trait and brain GMV feature in long-term abstinent individuals with severe methamphetamine use disorder. Moreover, our findings suggest that lower GMV in the right superior frontal cortex might reflect a trait marker of higher impulsivity in this population.

Determining factors for Cannabis use among Moroccans Schizophrenic Patients: A cross sectional study

OBJECTIVE

Cannabis use is considered a major clinical problem associated with a poorer outcome in patients with schizophrenia. The objective of the present study was to assess the prevalence of cannabis us among patients with schizophrenia. The assessment consists in comparing some factors related to substance use in a population of schizophrenic patients between cannabis users and non.

MATERIALS AND METHODS

Four hundred and three participants who were examined prospectively during their hospitalization answered the PANNS scale of schizophrenia, GAF, BIS-10, CDSS, and MARS. The consumption of cannabis was investigated using urine toxicological analysis. Sociodemographic, clinical and therapeutic data were also recorded.

RESULTS

The prevalence of cannabis use among schizophrenic inpatients was 49%. Patients with cannabis use were younger (31.7 vs 34.9 years old, p<0.001), more often male (52 vs 20% female, p<0.001), and they presented more often a history of imprisonment (68.8% vs 31.2%, p<0.001). Patients who were users of cannabis had a lower age at onset of the disease than non-users (23.6 vs 24.8 years, p=0.029), and more often with poor medication adherence (p=0.001). Logistic regression revealed that factors associated with cannabis use among schizophrenics were the age, gender, history of imprisonment and poor medication adherence.

CONCLUSION

The study showed that a high prevalence of cannabis use among patients with schizophrenia which was associated with negative overall outcomes. Determining comorbid substance use disorders among schizophrenic patients is crucial as it may contribute to establish a better therapeutic strategy.

Impulsivity and compulsivity are differentially associated with automaticity and routine on the Creature of Habit Scale

Habits may develop when meaningful action patterns are frequently repeated in a stable environment. We measured the differing tendencies of people to form habits in a population sample of n = 533 using the Creature of Habit Scale (COHS). We confirmed the high reliability of the two latent factors measured by the COHS, automaticity and routines. Whilst automatic behaviours are triggered by context and do not serve a particular purpose or goal, routines often have purpose, and because they have been performed so often in a given context, they become automatic only after their action sequence has been activated. We found that both types of habitual behaviours are influenced by the frequency of their occurrence and they are differentially influenced by personality traits. Compulsive personality is associated with an increase in both aspects of habitual tendency, whereas impulsivity is linked with increased automaticity, but reduced routine behaviours. Our findings provide further evidence that the COHS is a useful tool for understanding habitual tendencies in the general population and may inform the development of therapeutic strategies that capitalise on functional habits and help to treat dysfunctional ones.

Affect-driven impulsivity impairs human action control and selection, as measured through Pavlovian instrumental transfer and outcome devaluation

Two experiments were designed to study the role of emotional impulsiveness in action control and selection, involving healthy young women participants. In Experiment 1, the effects of both outcome devaluation and Pavlovian-to-instrumental transfer (PIT) were assessed on instrumental responding. In Experiment 2, we further explored the effect of outcome devaluation on outcome-specific PIT. The role of emotional impulsivity, specifically negative urgency (NU), was also evaluated in both experiments using a self-reported measure (UPPS-P scale, Spanish short version). Experiment 1 showed both outcome devaluation and outcome-specific PIT effects, which were positively inter-correlated and negatively correlated with scores in NU. Experiment 2 found an effect of outcome devaluation on outcome-specific PIT, which was negatively correlated with scores on NU. These results highlight the relevance of considering individual differences in affect-driven impulsivity, specifically NU, when addressing failures in action control and selection (proneness to habit). Moreover, these findings suggest that, at least with the procedure used in these experiments, outcome-specific PIT may be based on a goal-directed process that is under the participant's control.

A Working Hypothesis for the Role of the Cerebellum in Impulsivity and Compulsivity

Growing evidence associates cerebellar abnormalities with several neuropsychiatric disorders in which compulsive symptomatology and impulsivity are part of the disease pattern. Symptomatology of autism, addiction, obsessive-compulsive (OCD), and attention deficit/hyperactivity (ADHD) disorders transcends the sphere of motor dysfunction and essentially entails integrative processes under control of prefrontal-thalamic-cerebellar loops. Patients with brain lesions affecting the cortico-striatum thalamic circuitry and the cerebellum indeed exhibit compulsive symptoms. Specifically, lesions of the posterior cerebellar vermis cause affective dysregulation and deficits in executive function. These deficits may be due to impairment of one of the main functions of the cerebellum, implementation of forward internal models of the environment. Actions that are independent of internal models may not be guided by predictive relationships or a mental representation of the goal. In this review article, we explain how this deficit might affect executive functions. Additionally, regionalized cerebellar lesions have been demonstrated to impair other brain functions such as the emergence of habits and behavioral inhibition, which are also altered in compulsive disorders. Similar to the infralimbic cortex, clinical studies and research in animal models suggest that the cerebellum is not required for learning goal-directed behaviors, but it is critical for habit formation. Despite this accumulating data, the role of the cerebellum in compulsive symptomatology and impulsivity is still a matter of discussion. Overall, findings point to a modulatory function of the cerebellum in terminating or initiating actions through regulation of the prefrontal cortices. Specifically, the cerebellum may be crucial for restraining ongoing actions when environmental conditions change by adjusting prefrontal activity in response to the new external and internal stimuli, thereby promoting flexible behavioral control. We elaborate on this explanatory framework and propose a working hypothesis for the involvement of the cerebellum in compulsive and impulsive endophenotypes.

Investigating the balance between goal-directed and habitual control in experimental and real-life settings

Do people differ in their propensity to form habits? The current study related individual differences in habitual performance on the slips-of-action task to habit formation in real life. To this end, we developed a novel key-cover procedure that controls for the amount of repetition and motivation within a naturalistic setting. Participants received a key cover for the key to their home, which after several weeks was switched with a key cover that was previously attached to a dummy key. Participants recorded effort, time, attention, and mistakes in the key-selection process. Results were in line with established properties of habits, as attention decreased in the learning phase, yet effort, time, and mistakes increased after the key-cover switch. Performance on the slips-of-action task correlated negatively with changes in attention in the real-life key-cover task. This negative correlation may reflect that flexible behavioral adjustment requires more attention in people with a relatively weak goal-directed system.

The extended evolutionary synthesis and addiction: the price we pay for adaptability

Humans are more likely to become addicted and to stay addicted than are other animals. This chapter is a neurobiological and molecular review of addiction and the cooccurring traits and psychiatric disorders from the perspective of the Extended Evolutionary Synthesis (EES). Addiction is an example of pleiotropy as many common haplotypes that are associated with individual differences in vulnerability to substance dependence express a variety of important brain-based phenotypes such as neuroadaptive processes. The neurochemical mechanisms of addiction are shared with behavioral flexibility and the ability to innovate, which are hallmark features of our species. The dopaminergic system provides a link between addiction and the cooccurring traits and psychiatric disorders evident in the shared genetic profile. A hypofunctioning dopaminergic system is also a common characteristic feature of addiction and the cooccurring traits and psychiatric disorders. Epigenetics allows for environmental factors to create lasting and heritable phenotypic changes enabling rapid adaptation to an environment. Addiction "high-jacks" this system as well as the neurochemical mechanisms that control flexibility and innovation and is, thus, the price we pay for adaptability.

GABRB1 Single Nucleotide Polymorphism Associated with Altered Brain Responses (but not Performance) during Measures of Impulsivity and Reward Sensitivity in Human Adolescents

Variations in genes encoding several GABA_A receptors have been associated with human drug and alcohol abuse. Among these, a number of human studies have suggested an association between GABRB1, the gene encoding GABA_A receptor β1 subunits, with Alcohol dependence (AD), both on its own and comorbid with other substance dependence and psychiatric illnesses. In the present study, we hypothesized that the GABRB1 genetically-associated increased risk for developing alcoholism may be associated with impaired behavioral control and altered sensitivity to reward, as a consequence of altered brain function. Exploiting the IMAGEN database (Schumann et al., 2010), we explored in a human adolescent population whether possession of the minor (T) variant of the single nucleotide polymorphism (SNP) rs2044081 is associated with performance of tasks measuring aspects of impulsivity, and reward sensitivity that are implicated in drug and alcohol abuse. Allelic variation did not associate with altered performance in either a stop-signal task (SST), measuring one aspect of impulsivity, or a monetary incentive delay (MID) task assessing reward anticipation. However, increased functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent (BOLD) response in the right hemisphere inferior frontal gyrus (IFG), left hemisphere caudate/insula and left hemisphere inferior temporal gyrus (ITG) during MID performance was higher in the minor (T) allelic group. In contrast, during SST performance, the BOLD response found in the right hemisphere supramarginal gyrus, right hemisphere lingual and left hemisphere inferior parietal gyrus indicated reduced responses in the minor genotype. We suggest that β1-containing GABA_A receptors may play a role in excitability of brain regions important in controlling reward-related behavior, which may contribute to susceptibility to addictive behavior.

Psychological Factors and Alcohol Use in Problematic Mobile Phone Use in the Spanish Population

This research aims to study the existing relationships among the factors of state anxiety, depression, impulsivity, and alcohol consumption regarding problematic mobile phone use, as assessed by the Mobile Phone Problem Use Scale. The study was conducted among 1,126 participants recruited among the general Spanish population, aged 16-65 years, by assessing the predictive value of these variables regarding this problematic use. Initially tobacco use was also considered being subsequently refused because of the low internal consistency of the scale used. In general terms, the results show that this problematic use is mainly related to state anxiety and impulsivity, through the dimensions of Positive and Negative Urgency. Considering its predictive value, multiple regression analysis reveals that state anxiety, positive and negative urgency, and alcohol consumption may predict problematic mobile phone use, ruling out the influence of depression.

Etiological theories of addiction: A comprehensive update on neurobiological, genetic and behavioural vulnerability

Currently, about 246 million people around the world have used an illicit drug. The reasons for this use are multiple: e.g. to augment the sensation of pleasure or to reduce the withdrawal and other aversive effects of a given substance. This raises the problem of addiction, which remains a disease of modern society. This review offers a comprehensive update of the different theories about the etiology of addictive behaviors with emphasis on the neurobiological, environmental, psychopathological, behavioural and genetic aspects of addictions, discussed from an evolutionary perspective. The main conclusion of this review is that vulnerability to drug addiction suggests an interaction between many brain systems (including the reward, decision-making, serotonergic, oxytocin, interoceptive insula, CRF, norepinephrine, dynorphin/KOR, orexin and vasopressin systems), genetic predisposition, sociocultural context, impulsivity and drugs types. Further advances in biological and psychological science are needed to address the problems of addiction at its roots.

Risk Factors for Addiction and Their Association with Model-Based Behavioral Control

Addiction shows familial aggregation and previous endophenotype research suggests that healthy relatives of addicted individuals share altered behavioral and cognitive characteristics with individuals suffering from addiction. In this study we asked whether impairments in behavioral control proposed for addiction, namely a shift from goal-directed, model-based toward habitual, model-free control, extends toward an unaffected sample (n = 20) of adult children of alcohol-dependent fathers as compared to a sample without any personal or family history of alcohol addiction (n = 17). Using a sequential decision-making task designed to investigate model-free and model-based control combined with a computational modeling analysis, we did not find any evidence for altered behavioral control in individuals with a positive family history of alcohol addiction. Independent of family history of alcohol dependence, we however observed that the interaction of two different risk factors of addiction, namely impulsivity and cognitive capacities, predicts the balance of model-free and model-based behavioral control. Post-hoc tests showed a positive association of model-based behavior with cognitive capacity in the lower, but not in the higher impulsive group of the original sample. In an independent sample of particularly high- vs. low-impulsive individuals, we confirmed the interaction effect of cognitive capacities and high vs. low impulsivity on model-based control. In the confirmation sample, a positive association of omega with cognitive capacity was observed in highly impulsive individuals, but not in low impulsive individuals. Due to the moderate sample size of the study, further investigation of the association of risk factors for addiction with model-based behavior in larger sample sizes is warranted.

Negative mood reverses devaluation of goal-directed drug-seeking favouring an incentive learning account of drug dependence

BACKGROUND

Two theories explain how negative mood primes smoking behaviour. The stimulus-response (S-R) account argues that in the negative mood state, smoking is experienced as more reinforcing, establishing a direct (automatic) association between the negative mood state and smoking behaviour. By contrast, the incentive learning account argues that in the negative mood state smoking is expected to be more reinforcing, which integrates with instrumental knowledge of the response required to produce that outcome.

OBJECTIVES

One differential prediction is that whereas the incentive learning account anticipates that negative mood induction could augment a novel tobacco-seeking response in an extinction test, the S-R account could not explain this effect because the extinction test prevents S-R learning by omitting experience of the reinforcer.

METHODS

To test this, overnight-deprived daily smokers (n = 44) acquired two instrumental responses for tobacco and chocolate points, respectively, before smoking to satiety. Half then received negative mood induction to raise the expected value of tobacco, opposing satiety, whilst the remainder received positive mood induction. Finally, a choice between tobacco and chocolate was measured in extinction to test whether negative mood could augment tobacco choice, opposing satiety, in the absence of direct experience of tobacco reinforcement.

RESULTS

Negative mood induction not only abolished the devaluation of tobacco choice, but participants with a significant increase in negative mood increased their tobacco choice in extinction, despite satiety.

CONCLUSIONS

These findings suggest that negative mood augments drug-seeking by raising the expected value of the drug through incentive learning, rather than through automatic S-R control.

Evidence that a volitional help sheet reduces alcohol consumption among smokers: a pilot randomized controlled trial

Cigarette smokers have greater problems with alcohol than members of the general population, due partly to the influence of smoking on alcohol consumption. The present study was designed to test the ability of implementation intentions to reduce alcohol consumption among cigarette smokers. Sixty-five smokers (37 women, 28 men; age M=33.77, SD=9.69) were randomly allocated to an active control condition (n=31) or were asked to form implementation intentions using a volitional help sheet (n=34). The outcome measure was subsequent alcohol intake, measured 1-month postbaseline. There was a significant decrease in alcohol consumption in the intervention group but not in the control condition. At the end of the study, alcohol consumption had decreased significantly, by 2.00 standard units (i.e., 16 grams alcohol) per week in the intervention group, but had increased marginally (by 0.46 standard units per week) in the active control condition (d=0.63). The findings support the efficacy of the volitional help sheet to reduce alcohol consumption among smokers. Further research is needed to refine the volitional help sheet and explore its efficacy among other at-risk groups.

A hierarchical instrumental decision theory of nicotine dependence

It is important to characterize the learning processes governing tobacco-seeking in order to understand how best to treat this behavior. Most drug learning theories have adopted a Pavlovian framework wherein the conditioned response is the main motivational process. We favor instead a hierarchical instrumental decision account, wherein expectations about the instrumental contingency between voluntary tobacco-seeking and the receipt of nicotine reward determines the probability of executing this behavior. To support this view, we review titration and nicotine discrimination research showing that internal signals for deprivation/satiation modulate expectations about the current incentive value of smoking, thereby modulating the propensity of this behavior. We also review research on cue-reactivity which has shown that external smoking cues modulate expectations about the probability of the tobacco-seeking response being effective, thereby modulating the propensity of this behavior. Economic decision theory is then considered to elucidate how expectations about the value and probability of response-nicotine contingency are integrated to form an overall utility estimate for that option for comparison with qualitatively different, nonsubstitute reinforcers, to determine response selection. As an applied test for this hierarchical instrumental decision framework, we consider how well it accounts for individual liability to smoking uptake and perseveration, pharmacotherapy, cue-extinction therapies, and plain packaging. We conclude that the hierarchical instrumental account is successful in reconciling this broad range of phenomenon precisely because it accepts that multiple diverse sources of internal and external information must be integrated to shape the decision to smoke.

Smokers report greater demand for alcohol on a behavioral economic purchase task

OBJECTIVE

Cigarette smokers have higher levels of alcohol consumption than nonsmokers and poorer response to alcohol treatment. It is possible that the greater severity of alcohol problems observed in smokers reflects a greater susceptibility to alcohol-related reinforcement. The present study used a behavioral economic purchase task to investigate whether heavy drinking smokers would have greater demand for alcohol than heavy drinking nonsmokers.

METHOD

Participants were 207 college students who reported at least one heavy drinking episode in the past month. Of the 207 participants, 33.2% (n = 67) reported smoking cigarettes at least 1 day in the past month. Participants completed the hypothetical alcohol purchase task, a simulation task that asked them to report how many drinks they would purchase at varying price increments.

RESULTS

After the participants' reported alcohol consumption, gender, alcohol problems, and depression were controlled for, analyses of covariance revealed that heavy drinking smokers had significantly greater reported maximum alcohol expenditures (Omax), greater maximum inelastic price (Pmax), and higher breakpoint values (first price suppressing consumption to zero).

CONCLUSIONS

College student heavy drinkers who also smoke cigarettes exhibit increased demand for alcohol. Smokers in this high-risk developmental stage may thus be less sensitive to price and other contingencies that would otherwise serve to modulate drinking and may require more intensive intervention approaches.

BIS impulsivity and acute nicotine exposure are associated with discounting global consequences in the Harvard game

OBJECTIVE

The Barratt Impulsivity Scale (BIS) provides a transdiagnostic marker for a number of psychiatric conditions and drug abuse, but the precise psychological trait(s) tapped by this questionnaire remain obscure.

METHOD

To address this, 51 smokers completed in counterbalanced order the BIS, a delay discounting task and a Harvard game that measured choice between a response that yielded a high immediate monetary payoff but decreased opportunity to earn money overall (local choice) versus a response that yielded a lower immediate payoff but afforded a greater opportunity to earn overall (global choice).

RESULTS

Individual level of BIS impulsivity and self-elected smoking prior to the study were independently associated with increased preference for the local over the global choice in the Harvard game, but not delay discounting.

CONCLUSIONS

BIS impulsivity and acute nicotine exposure reflect a bias in the governance of choice by immediate reward contingencies over global consequences, consistent with contemporary dual-process instrumental learning theories.

Associative learning mechanisms underpinning the transition from recreational drug use to addiction

Learning theory proposes that drug seeking is a synthesis of multiple controllers. Whereas goal-directed drug seeking is determined by the anticipated incentive value of the drug, habitual drug seeking is elicited by stimuli that have formed a direct association with the response. Moreover, drug-paired stimuli can transfer control over separately trained drug seeking responses by retrieving an expectation of the drug's identity (specific transfer) or incentive value (general transfer). This review covers outcome devaluation and transfer of stimulus-control procedures in humans and animals, which isolate the differential governance of drug seeking by these four controllers following various degrees of contingent and noncontingent drug exposure. The neural mechanisms underpinning these four controllers are also reviewed. These studies suggest that although initial drug seeking is goal-directed, chronic drug exposure confers a progressive loss of control over action selection by specific outcome representations (impaired outcome devaluation and specific transfer), and a concomitant increase in control over action selection by antecedent stimuli (enhanced habit and general transfer). The prefrontal cortex and mediodorsal thalamus may play a role in this drug-induced transition to behavioral autonomy.

'Risking enchantment': how are we to view the smoking person?

The idea of the smoking person portrayed in public health has been criticised as being based on too narrow a view of human nature. This article discusses that view: that of a person with a stable core and epiphenomenal 'behaviours' that can be removed by rational persuasion or Pavlovian manipulation, and examines social scientific critiques of it. The social sciences explore the meanings smoking has for individuals and portray human identity as malleable, the result of ongoing interactions with human and non-human others. Aspects of smokers' experience revealed in qualitative research - descriptions of cigarettes as 'companions' or 'friends', deep reliance, sensual pleasure - are sometimes difficult to articulate but can be given full voice in the context of the literary arts. We explore some examples of these sources and argue that a complete picture of smoking meanings is impossible without reference to them. We take a pragmatic approach, following the philosopher William James, who argued that emotional and spiritual experiences contribute to the truth of human existence as much as material explanations, to suggest that this understanding should be part of a critical but supportive engagement with public health research in order to develop more nuanced and humane approaches to smoking cessation.

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 it 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 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.

Effect of craving induction on inhibitory control in opiate dependence

RATIONALE

Current neurobiological models of addiction posit that drug seeking is much more likely to occur during emotionally charged states (such as craving), as deficits in inhibitory control become more pronounced during heightened motivational states.

OBJECTIVE

The purpose of this study was to examine the effect of cue-induced craving states on attention and inhibitory control within addicted individuals.

METHODS

We tested the performance of 39 opiate-dependent individuals on cognitive measures of attention (Digit Span, Digit Symbol, and Telephone Search) and inhibitory control (Counting Stroop and Go-No-Go) both before and after exposure to an autobiographical craving script. A non-drug using healthy control group (n = 19) performed the same tasks before and after listening to a relaxation tape.

RESULTS

Following craving induction, opiate-dependent individuals demonstrated improved performance on tests of processing speed and attentional span (consistent with the practice effect observed in controls) and increased their response errors on the Stroop task (in contrast to controls), while selective attention was unaffected. Individual differences in compulsivity mediated the association between craving and Stroop performance, such that low-compulsive (but not high-compulsive) individuals committed more response errors after craving induction.

CONCLUSIONS

These findings challenge the notion of cue-induced craving as a primary trigger of disrupted cognition and drug-seeking behavior in addicted individuals, and raise the need to explore individual differences in compulsivity when addressing the links between craving and loss of control within research and clinical settings.

Impulsivity and symptoms of nicotine dependence in a young adult population

Introduction:

Impulsivity is widely regarded as a risk factor for drug dependence. However, its relationship with the symptomatology of nicotine dependence is poorly understood.

Methods:

To examine the nature of these relationships, we recruited 404 daily and occasional smokers from a predominantly student population and assessed the association between impulsivity, as measured by the Barratt Impulsiveness Scale (BIS-11) and several self-reported measures of smoking rate and nicotine dependence, including the Diagnostic and Statistical Manual’s (DSM-IV) criteria.

Results:

Overall, impulsivity was high throughout the entire sample but only modestly associated with nicotine dependence. Within the diagnostic criteria of nicotine dependence, two symptoms, which reflect automatized or habitual smoking, were most strongly associated with impulsivity.

Conclusion:

These data support recent human and animal work, which suggests that impulsivity is linked to the formation of habitual drug use, and are discussed within the framework of a dual-system account of drug seeking.

The science of making drug-addicted animals

Research involving animal models of drug addiction can be viewed as a sort of reverse psychiatry. Contrary to clinicians who seek to treat addicted people to become and remain abstinent, researchers seek to make drug-naïve animals addicted to a drug with known addictive properties in humans. The goals of this research are to better understand the neuroscience of drug addiction and, ultimately, to translate this knowledge into effective treatments for people with addiction. The present review will not cover the vast literature that has accumulated over the past 50 years on animal models of drug addiction. It is instead more modestly devoted to recent research spanning the past decade on drug self-administration-based models of addiction in the rat (the animal species most frequently used in the field), with a special focus on current efforts to model compulsive cocaine use as opposed to nonaddictive use. Surprisingly, it turns out that modeling compulsive cocaine use in rats is possible but more difficult than previously thought. In fact, it appears that resilience to cocaine addiction is the norm in rats. As in human cocaine users, only few individual rats would be vulnerable. This conclusion has several important implications for future research on the neuroscience of cocaine addiction and on preclinical medication development.