Disrupted 'reflection' impulsivity in cannabis users but not current or former ecstasy users

Is impulsivity related to attentional bias in cigarette smokers? An exploration across levels of nicotine dependency and deprivation

Research has largely focused on how attentional bias to smoking-related cues and impulsivity independently influence the development and maintenance of cigarette smoking, with limited exploration of the relationship between these mechanisms. The current experiments systematically assessed relationships between multiple dimensions of impulsivity and attentional bias, at different stages of attention, in smokers varying in nicotine dependency and deprivation. Nonsmokers (NS; n  = 26), light-satiated smokers (LS; n  = 25), heavy-satiated smokers (HS; n  = 23) and heavy 12-hour nicotine-deprived smokers (HD; n  = 30) completed the Barratt Impulsivity Scale, delayed discounting task, stop-signal task, information sampling task and a visual dot-probe assessing initial orientation (200 ms) and sustained attention (2000 ms) toward smoking-related cues. Sustained attention to smoking-related cues was present in both HS and LS, while initial orientation bias was only evident in HS. HS and LS also had greater levels of trait motor and nonplanning impulsivity and heightened impulsive choice on the delay discounting task compared with NS, while heightened trait attentional impulsivity was only found in HS. In contrast, in HD, nicotine withdrawal was associated with no attentional bias but heightened reflection impulsivity, poorer inhibitory control and significantly lower levels of impulsive choice relative to satiated smokers. Trait and behavioral impulsivity were not related to the extent of attentional bias to smoking-related cues at any stage of attention, level of nicotine dependency or state of deprivation. Findings have both clinical and theoretical implications, highlighting the unique and independent roles impulsivity and attentional bias may play at different stages of the nicotine addiction cycle.

Jumping to conclusions bias, psychosis and impulsivity in early stages of Parkinson's disease

OBJECTIVES

The aim was to explore the correlations between Jumping to Conclusions (JtC) tendency and neuropsychiatric features in patients with early Parkinson's disease (PD).

BACKGROUND

According to few reports, PD patients with impulsive-compulsive behaviors (ICBs) are prone to working memory difficulties including JtC bias. The correlation of psychotic features and JtC tendency remains still unclear.

METHODS

Healthy controls and patients within 3 years of PD onset were recruited. Participants were examined for psychotic symptoms using a 10 question PD-specific psychosis severity scale. JtC was measured by a probalistic reasoning scenario (beads task). In PD group, medication use, motor and non-motor symptoms were documented. Impulsivity was evaluated using the Questionnaire for Impulsive-Compulsive Disorders in PD (QUIP).

RESULTS

The prevalence of JtC bias was 9% (6/70) in healthy individuals, compared to 32% (22/68) of PD group [p = 0.001]. No association was detected between the presence of JtC tendency and PD-associated psychosis (p = 0.216). Patients with JtC had shorter duration of PD, more tremor-dominant PD subtype and higher QUIP scores, regardless of the dopaminergic therapy (p = 0.043, p = 0.015, p = 0.007, respectively). A trend towards attention and inhibition control deficit was noticed in JtC patients.

CONCLUSIONS

We found a high prevalence of JtC bias in early, cognitively intact PD population and a potential link between subthreshold ICBs and poor performance on beads task. Additional studies are needed to confirm our results and elaborate on the mechanisms that correlate impulsivity with JtC tendency, which are likely to be different from those mediating psychotic features in early PD.

Testing the validity and reliability of the Matching Familiar Figures Test-2021: An updated behavioral measure of reflection–impulsivity

The Matching Familiar Figures Test (MFFT) is a well-known and extensively used behavioral measure of reflection-impulsivity. However, the instrument has several deficiencies, including images designed for school-age children in the United States during the 1960s. Most importantly, an adult version of the instrument is currently unavailable and the lack of a single repository for the images raises questions regarding the MFFT’s validity and reliability. We developed a 21st century version of the MFFT using images that are familiar to adults and reside in a freely accessible repository. We conducted two studies examining validity and reliability issues. In Study 1, participants interacting with the MFFT-2021, versus those interacting with the original MFFT20, spent more time on the task, took more time in making their first response, and were more likely to complete the task without errors, even though the average number of errors was higher than the comparison group. The coherence of these results is evidence of convergent validity. Regarding predictive validity, the MFFT-2021 remained a reliable predictor of rational thinking, such that participants who demonstrated more reflection (less impulsivity) tended to avoid rational thinking errors. Also, performance on the MFFT-2021 predicted higher quality judgments in processing job characteristic cues with embedded interactions, a form of configural information processing. We also found evidence of concurrent validity: performance on the MFFT-2021 differed in a predictable manner for participants grouped by their performance on the Cognitive Reflection Test. In Study 2, we tested discriminant validity by comparing participant performance on the MFFT-2021 to their performance on the Information Sampling Task (IST), another behavioral measure of reflection-impulsivity used in studies of psychopharmacological and addiction behaviors. For our participants (undergraduate business students), we found that the MFFT was a stronger predictor of performance on rational thinking tasks, and, contrary to prior studies, our exploratory factor analysis identified separate factors for the MFFT-2021 and the IST, supporting discriminant validity, indicating that these two instruments measure different subtypes of reflection-impulsivity.

Synaptosomal-Associated Protein 25 Gene Polymorphisms Affect Treatment Efficiency of Methylphenidate in Children With Attention-Deficit Hyperactivity Disorder: An fNIRS Study

Methylphenidate (MPH) is the first-line drug for the treatment of children with attention-deficit hyperactivity disorder (ADHD); however, individual curative effects of MPH vary. Many studies have demonstrated that synaptosomal-associated protein 25 (SNAP-25) gene MnlI polymorphisms may be related to the efficacy of MPH. However, the association between SNAP-25MnlI polymorphisms and changes in brain hemodynamic responses after MPH treatment is still unclear. This study used functional near-infrared spectroscopy (fNIRS) to preliminarily investigate the interaction of MPH treatment-related prefrontal inhibitory functional changes with the genotype status of the SNAP-25 gene in children with ADHD. In total, 38 children with ADHD aged 6.76–12.08 years were enrolled in this study and divided into the following two groups based on SNAP-25 gene MnlI polymorphisms: T/T genotype group (wild-type group, 27 children) and G allele carrier group (mutation group, 11 children). The averaged oxygenated hemoglobin concentration changes [Δavg oxy-Hb] and deoxyhemoglobin concentration changes [Δavg deoxy-Hb] in the frontal cortex before MPH treatment and after 1.5 h (post-MPH1.5h) and 4 weeks (post-MPH4w) of MPH treatments were monitored using fNIRS during the go/no-go task. SNAP-IV scores were evaluated both pre-MPH and post-MPH4w treatments. In the T/T genotype group, [Δavg oxy-Hb] in the dorsolateral prefrontal cortex was significantly higher after 4 weeks of MPH (post-MPH4W) treatment than pre-treatment; however, in the G allele group, no significant differences in [Δavg oxy-Hb] were observed between pre- and post-treatments. In the go/no-go task, the accuracy was significantly increased post-MPH4w treatment in the T/T genotype group, while no significant differences were observed in response time and accuracy of the “go” sand no-go task in the G allele group for pre-MPH, post-MPH1.5h, and post-MPH4w treatments. The T/T genotype group exhibited a significant decrease in SNAP-IV scores after MPH treatment, while the G allele group showed no significant difference. In conclusion, fNIRS data combined with SNAP-25 MnlI polymorphism analysis may be a useful biomarker for evaluating the effects of MPH in children with ADHD.

The acute and non-acute effects of cannabis on reward processing: A systematic review

Cannabis use has historically been thought to cause amotivation, but the relationship between cannabis and apathy, anhedonia, and reward processing remains poorly characterised. In this systematic review, we evaluated whether cannabis exposure acutely and/or non-acutely was associated with altered reward processing using questionnaire, behavioural, or functional neuroimaging measures. Questionnaire studies demonstrated greater anhedonia in adolescent cannabis users, and some indication of greater apathy in young adult cannabis users. Behavioural studies yielded some evidence of reduced reward learning in adolescent cannabis users, though there were too few studies in this category for reliable conclusions. Finally, longitudinal and acute functional neuroimaging studies showed an association between cannabis and blunted neural responses to reward, which did not emerge consistently in cross-sectional studies. The current results suggest that cannabis use is associated with specific impairments in reward and motivation. Future large-scale, longitudinal studies which use multiple behavioural and neuroimaging measures of reward processing may further clarify the impact of cannabis use on motivational and reward processes, and neural networks.

Sex Differences in Neuropsychological Functioning are Domain-Specific in Adolescent and Young Adult Regular Cannabis Users

OBJECTIVE

Adolescence into young adulthood represents a sensitive period in which brain development significantly diverges by sex. Regular cannabis use by young people is associated with neuropsychological vulnerabilities, but the potential impact of sex on these relationships is unclear.

METHOD

In a cross-sectional study, we examined sex differences in multi-domain neuropsychological functioning using the Cambridge Neuropsychological Test Automated Battery (CANTAB) and tested whether sex moderated the relationship between cognitive performance and age of initiation, frequency of cannabis use, amount of cannabis use, and withdrawal symptoms in at least weekly adolescent and young adult cannabis users (n = 171; aged 13-25 years; 46.2% female).

RESULTS

Male cannabis users had poorer visual recognition memory and female cannabis users showed worse attention and executive functions, with medium to large effect sizes. These sex effects persisted, when controlling for age, IQ, amount of alcohol and nicotine use, mood and anxiety symptoms, emotional stability and impulsive behavior. Earlier age of initiated use and more use were associated with worse attentional functions in females, but not males. More use was more strongly associated with worse episodic memory in males than in females. More use was associated with poorer learning in males only.

CONCLUSIONS

Domain-specific patterns of neuropsychological performance were found by sex, such that males showed poorer visual memory and females showed worse performance on measures of attention (sustained visual, multitasking) and executive functioning (spatial planning/working memory subdomains). Larger studies including healthy controls are needed to determine if the observed sex differences are more exaggerated relative to non-users.

Selective effects of serotonin on choices to gather more information

BACKGROUND

Gathering and evaluating information leads to better decisions, but often at cost. The balance between information seeking and exploitation features in neurodevelopmental, mood, psychotic and substance-related disorders. Serotonin's role has been highlighted by experimental reduction of its precursor, tryptophan.

AIMS

We tested the boundaries and applicability of this role by asking whether changes to information sampling would be observed following acute doses of serotonergic and catecholaminergic clinical treatments. We used a variant of the Information Sampling Task (IST) to measure how much information a person requires before they make a decision. This task allows participants to sample information until satisfied to make a choice.

METHODS

In separate double-blind placebo-controlled experiments, we tested 27 healthy participants on/off 20 mg of the serotonin reuptake inhibitor (SRI) citalopram, and 22 participants on/off 40 mg of the noradrenergic reuptake inhibitor atomoxetine. The IST variant minimised effects of temporal impulsivity and loss aversion. Analyses used a variety of participant prior expectations of sampling spaces in the IST, including a new prior that accounts for learning of likely states across trials. We analysed behaviour by a new method that also accounts for baseline individual differences of risk preference.

RESULTS

Baseline preferences demonstrated risk aversion. Citalopram decreased the expected utility of choices and probability of being correct based on informational content of samples collected, suggesting participants collected less useful information before making a choice. Atomoxetine did not influence information seeking.

CONCLUSION

Acute changes of serotonin activity by way of a single SRI dose alter information-seeking behaviour.

Disentangling the effects of cannabis and cigarette smoking on impulsivity

BACKGROUND

Cannabis smoking and cigarette smoking often co-occur, yet limited research has investigated the potentially different role impulsivity may play when these behaviours occur in isolation, compared with in combination.

AIMS

This study examined trait and behavioural impulsivity as a function of both cigarette and cannabis smoking.

METHODS

Trait impulsivity (BIS-11) was compared between 44 non-smokers, 76 cigarette only, 47 cannabis only and 58 cannabis plus cigarette smokers. The effects of cigarette and cannabis smoking on behavioural impulsivity (stop-signal and information sampling tasks) were then assessed in 87 of these participants during a laboratory session.

RESULTS

Trait impulsivity was significantly higher in cigarette smokers than non-smokers, irrespective of cannabis use, except for motor impulsivity, where cigarette smoking was only associated with elevated trait impulsivity in non-smokers of cannabis. Dimensions of trait impulsivity were significantly positively related to cigarette smoking frequency and nicotine dependence, but not to cannabis smoking frequency or dependence. Smoking cigarettes or cannabis was associated with significantly impaired reflection impulsivity relative to not smoking either substance. However, no additional increases in reflection impulsivity were observed in those who smoked both cigarettes and cannabis. No group differences in response inhibition were detected.

CONCLUSIONS

Heightened trait impulsivity appears to be uniquely related to cigarette smoking, whilst the smoking of cigarettes or cannabis is associated with impairments in reflection impulsivity. Improved outcomes for treating cannabis dependence may result from encouraging concomitant cigarette smokers to cease using both drugs simultaneously in order to reduce heightened impulsivity and risk of relapse.

Birth weight and catch up growth are associated with childhood impulsivity in two independent cohorts

Individuals born after intrauterine growth restriction (IUGR) are more impulsive towards palatable foods, but it is not clear 1) if IUGR-related impulsivity is specific for foods and solely based on response inhibition and 2) if the development of impulsivity is due to being born IUGR per se or to growing up fast in the first few years of life (catch up growth). Children were classified in the IUGR group if the birth weight ratio was below 0.85. Delta z score for BMI was used as a measure of catch up growth. In MAVAN (N = 274), impulsivity was measured by the Information Sampling Task from the Cambridge Neuropsychological Test Automated Battery (IST - CANTAB), and in GUSTO using the Sticker Delay Task (N = 327). There is a significant effect of interaction between being born IUGR and the magnitude of catch up growth on the reflection impulsivity from IST-CANTAB at 60 months, in which greater catch up growth associates with greater impulsivity in the IST fixed condition in IUGR children. The finding was reproduced in children from the GUSTO cohort using the Sticker Delay Task. We confirmed that catch up growth interacts with IUGR, having a major role in the development of impulsivity in the first years of life and influencing inhibitory control and decision making processes.

Go/No-Go task performance predicts differences in compulsivity but not in impulsivity personality traits

Lack of inhibitory control is present in impulsive and compulsive personality traits. The Go/No-Go task is one of the most effective means to assess response inhibition measured by the ability to appropriately withhold responding to No-Go stimuli. The aim of this work was to study whether differences in performance of Go/No-Go task predicts differences in personality traits related to inhibitory control. For this purpose 63 healthy participants divided into two groups based on the median split of false alarms on the Go/No-Go task completed Barratt Impulsiveness Scale (BIS-11) and the Maudsley Obsessional Compulsive Questionnaire (MOCI). Results showed that participants with high false alarms (H-FA) displayed a high-risk strategy of responding, and higher scores in the MOCI Total and MOCI Checking subscale compared to participants with low false alarms (L-FA). The results show for the first time a relation between the execution of the Go/No-Go task and the MOCI scale. Surprisingly, no relation was found between the Go/No-Go task and the BIS-11 scale. Further studies are needed to define the heterogeneous constructs of compulsivity and impulsivity, and to improve the convergence of the clinical scales and the behavioral measures of these two personality traits.

Longitudinal changes in cognition in young adult cannabis users

INTRODUCTION

Adolescent cannabis use (CU) is associated with impaired attention, executive function, and verbal learning/memory. These associations are generally observed in cross-sectional studies. Longitudinal studies of cannabis users are lacking.

METHOD

The present study examines associations between CU and cognition over time in chronic daily adolescent-onset CUs, as compared to nonusing controls. Both groups completed a neuropsychological battery at study intake and again 2 years later.

RESULTS

Baseline group differences have been published and indicated deficits in verbal learning and memory, motivated decision-making, planning, and working memory in CUs. In this follow-up report, the longitudinal performance of users is compared to that of sustained nonusers using the same battery. At follow-up, the majority of CUs continued to report regular and heavy cannabis use. Relative impairments in the domains of working memory, planning and verbal memory remained stable, suggesting that these are enduring vulnerabilities associated with continued CU during young adulthood. Improvements in motivated decision-making were evident in both groups. In addition, CUs demonstrated relatively better performance on short-duration speeded tasks. An earlier age of CU onset was associated with poorer verbal learning and memory and planning performance over time.

CONCLUSIONS

Verbal learning and memory and planning processes, as well as their neural correlates, merit further scrutiny within etiological models of cannabis-induced cognitive impairments.

ADHD and cannabis use in young adults examined using fMRI of a Go/NoGo task

Children diagnosed with attention-deficit/hyperactivity disorder (ADHD) are at increased risk for substance abuse. Response inhibition is a hallmark of ADHD, yet the combined effects of ADHD and regular substance use on neural networks associated with response inhibition are unknown. Task-based functional Magnetic Resonance Imaging (fMRI) data from young adults with childhood ADHD with (n = 25) and without (n = 25) cannabis use ≥ monthly in the past year were compared with a local normative comparison group (LNCG) with (n = 11) and without (n = 12) cannabis use. Go/NoGo behavioral and fMRI data were evaluated for main and interaction effects of ADHD diagnosis and cannabis use. ADHD participants made significantly more commission errors on NoGo trials than controls. ADHD participants also had less frontoparietal and frontostriatal activity, independent of cannabis use. No main effects of cannabis use on response inhibition or functional brain activation were observed. An interaction of ADHD diagnosis and cannabis use was found in the right hippocampus and cerebellar vermis, with increased recruitment of these regions in cannabis-using controls during correct response inhibition. ADHD participants had impaired response inhibition combined with less fronto-parietal/striatal activity, regardless of cannabis use history. Cannabis use did not impact behavioral response inhibition. Cannabis use was associated with hippocampal and cerebellar activation, areas rich in cannabinoid receptors, in LNCG but not ADHD participants. This may reflect recruitment of compensatory circuitry in cannabis using controls but not ADHD participants. Future studies targeting hippocampal and cerebellar-dependent function in these groups may provide further insight into how this circuitry is altered by ADHD and cannabis use.

Executive Functioning in Pedophilia and Child Sexual Offending

OBJECTIVES

Pedophilia (P) is a psychiatric disease associated with sexual attraction toward children and often accompanied by child sexual offending (CSO). Consequently, it is important to address the understanding of executive dysfunctions that may increase the probability of CSO. Moreover, this research field has been lacking to disentangle executive deficits associated with pedophilia (as a deviant sexual preference) from those associated with CSO (as a deviant sexual behavior).

METHODS

The German multi-sided research network NeMUP offers the opportunity to overcome these limitations. By applying the Cambridge Automated Neuropsychological Test Battery in four carefully matched groups of men: (1) pedophiles with (N=45) and (2) without (N=45) a history of sexual offending against children; (3) child molesters without pedophilia (N=19), and (4) non-offending controls (N=49), we were able to analyze executive functioning in pedophilia and CSO independently.

RESULTS

Both CSO groups as compared to both non-CSO groups exhibited worsened response inhibition ability. However, only non-pedophilic offenders showed additionally disabled strategy use ability. Regarding set-shifting abilities, the P+CSO group showed the best performance. We also found that performances were affected by age: only in pedophiles, response inhibition worsened with age, while age-related deficits in set-shifting abilities were restricted to non-pedophilic participants. The latter also differentiated between both sexual preference groups.

CONCLUSIONS

Our results are the first to demonstrate that executive dysfunctions are related to offense status rather than pedophilic preference. Furthermore, there was evidence for differentiating age and performance correlations between pedophiles and non-pedophiles, which warrants further investigation. (JINS, 2017, 23, 460-470).

Understanding self-reported difficulties in decision-making by people with autism spectrum disorders

Autobiographical accounts and a limited research literature suggest that adults with autism spectrum disorders can experience difficulties with decision-making. We examined whether some of the difficulties they describe correspond to quantifiable differences in decision-making when compared to adults in the general population. The participants (38 intellectually able adults with autism spectrum disorders and 40 neurotypical adults) were assessed on three tasks of decision-making (Iowa Gambling Task, Cambridge Gamble Task and Information Sampling Task), which quantified, respectively, decision-making performance and relative attention to negative and positive outcomes, speed and flexibility, and information sampling. As a caution, all analyses were repeated with a subset of participants ( n_ASD = 29 and n_neurotypical = 39) who were not taking antidepressant or anxiolytic medication. Compared to the neurotypical participants, participants with autism spectrum disorders demonstrated slower decision-making on the Cambridge Gamble Task, and superior performance on the Iowa Gambling Task. When those taking the medications were excluded, participants with autism spectrum disorders also sampled more information. There were no other differences between the groups. These processing tendencies may contribute to the difficulties self-reported in some contexts; however, the results also highlight strengths in autism spectrum disorders, such as a more logical approach to, and care in, decision-making. The findings lead to recommendations for how adults with autism spectrum disorders may be better supported with decision-making.

Understanding Within-Session Loss-Chasing: An Experimental Investigation of the Impact of Stake Size on Cognitive Control

Loss-chasing is a central feature of problematic gambling, yet it remains a poorly conceived and understood concept. Loss-chasing is believed to stem from an erosion of cognitive control when gambling. The opportunity to gamble at significantly disparate stake sizes on a gambling activity is considered to be a risk factor for loss-chasing. This study investigated the impact of gambling at disparate stake sizes on executive processes integral to maintaining cognitive control when gambling, namely response inhibition and reflection impulsivity. Frequent adult non-problem gamblers (n = 32) participated in a repeated measures experiment; and gambled at three disparate stake sizes (£20, £2 and no stake per bet) on a simulated gambling task. Participants' response inhibition performance and reflection impulsivity levels after gambling at various stake sizes were compared via a go/no-go task and information sampling task, respectively. Quality of decision-making i.e. the evaluation of available information to make probability judgements was impaired after gambling at higher stakes in comparison to lower stakes, indicating an increase in reflection impulsivity. No effect on response inhibition was observed. Although exploratory, this suggests that the opportunity for participants to substantially increase stake size on a gambling activity may be a risk factor for impaired cognitive performance when gambling, and perhaps create vulnerability for within-session loss-chasing in some players.

Decision-making in chronic ecstasy users: a systematic review

Different cognitive impairments have been reported as a result of long-term MDMA/ecstasy use. Increased impulsivity and altered decision-making have been shown to be associated with the development and maintenance of addictive disorders pointing toward the necessity to understand a potential impairment of decision-making due to MDMA use. Thus, assessing the long-term effects of MDMA is crucial in order to evaluate its controversially discussed therapeutic use. The aim of this systematic review was to summarize the scientific literature on potential effects of chronic MDMA use on higher order decision-making processes in humans. Therefore, a systematic search for controlled trials relevant to the topic has been performed. Only studies using specific tasks on decision-making were included that involved subjects in the drug-free interval with drug-naïve, and/or polydrug control groups. A total of 12 studies could be identified that met the inclusion criteria, all of which were cross-sectional studies. The findings on decision-making disturbances in MDMA users were heterogeneous. Seven studies reported increased risky decisions, whereas five studies did not find MDMA-specific influences on decision-making. Increased impulsivity was observed both in MDMA groups and in (poly)drug control groups in almost all studies. Thus, the current state of research does not allow for the conclusion that long-term use of MDMA affects decision-making behavior in general. More detailed specifications as well as further investigations of the relevant processes are needed. Significant tendencies toward risky decision-making among long-term MDMA use have been observed, but need to be confirmed by studies using a longitudinal design.

Goal Management Training and Mindfulness Meditation improve executive functions and transfer to ecological tasks of daily life in polysubstance users enrolled in therapeutic community treatment

BACKGROUND

We have previously shown that Goal Management Training+Mindfulness Meditation (GMT+MM) improves executive functions in polysubstance users enrolled in outpatient treatment. The aim of this study was to establish if GMT+MM has similar positive effects on executive functions in polysubstance users in residential treatment, and if executive functions' gains transfer to more ecologically valid goal-oriented tasks.

METHODS

Thirty-two polysbustance users were randomly allocated to eight weeks of GMT+MM (n=16) or control, i.e., no-intervention (n=16); both groups received treatment as usual. Outcome measures included performance in laboratory tasks of basic and complex executive functions (i.e., basic: working memory and inhibition; complex: planning and self-regulation) and in an ecological task of goal-directed behavior (the Multiple Errands Test - contextualized version, MET-CV) measured post-interventions.

RESULTS

Results showed that GMT+MM was superior to control in improving basic measures of working memory (Letter-number sequencing; F=4.516, p=0.049) and reflection impulsivity (Information Sampling Test; F=6.217, p=0.018), along with initial thinking times during planning (Zoo Map Test; F=8.143, p=0.008). In addition, GMT+MM was superior to control in improving performance in the MET-CV (task failures; F=8.485, p=0.007).

CONCLUSION

Our findings demonstrate that GMT+MM increases reflective processes and the achievement of goals in daily activities, furthermore ecological test can detects changes easily than laboratory tasks.

Early onset marijuana use is associated with learning inefficiencies

OBJECTIVE

Verbal memory difficulties are the most widely reported and persistent cognitive deficit associated with early onset marijuana use. Yet, it is not known what memory stages are most impaired in those with early marijuana use.

METHOD

Forty-eight young adults, aged 18-25, who used marijuana at least once per week and 48 matched nonusing controls (CON) completed the California Verbal Learning Test, Second Edition (CVLT-II). Marijuana users were stratified by age of initial use: early onset users (EMJ), who started using marijuana at or before age 16 (n = 27), and late onset marijuana user group (LMJ), who started using marijuana after age 16 (n = 21). Outcome variables included trial immediate recall, total learning, clustering strategies (semantic clustering, serial clustering, ratio of semantic to serial clustering, and total number of strategies used), delayed recall, and percent retention.

RESULTS

Learning improved with repetition, with no group effect on the learning slope. EMJ learned fewer words overall than LMJ or CON. There was no difference between LMJ and CON in total number of words learned. Reduced overall learning mediated the effect on reduced delayed recall among EMJ, but not CON or LMJ. Learning improved with greater use of semantic versus serial encoding, but this did not vary between groups. EMJ was not related to delayed recall after adjusting for encoding.

CONCLUSIONS

Young adults reporting early onset marijuana use had learning weaknesses, which accounted for the association between early onset marijuana use and delayed recall. No amnestic effect of marijuana use was observed. (PsycINFO Database Record

Neurocognitive Functioning and Treatment Outcome Following Detoxification Among Asian Alcohol-Dependent Inpatients

BACKGROUND

The prevalence of alcohol use disorders in Asia is increasing and relapse among treated populations remains the norm, not the exception. The extent to which cognitive impairment influences clinical outcome remains unclear, with research dominated by studies of Caucasian populations.

OBJECTIVES

This study examines behavioral and self-reported cognitive functioning in detoxified alcohol-dependent (AD) patients in Singapore and its association with outcome.

METHODS

The cognitive performance of 30 recently-detoxified AD inpatients and 30 demographically-matched controls was compared using visuospatial memory, working memory, set-shifting, planning and reflection impulsivity tests of the CANTAB®, and self-reported dysexecutive symptoms and everyday cognitive difficulties. Patients' alcohol use and self-reported cognitive functioning were reassessed 3-months post-discharge.

RESULTS

Compared to matched controls, AD inpatients exhibited significantly poorer fluid intelligence, visuospatial memory, working memory, set-shifting flexibility and planning/organization, but not reflection impulsivity. In support of Western studies, a significant proportion (three-quarters) were "clinically impaired" on subtests. Significant reductions were observed in alcohol units, frequency and dependency scores at follow-up, though improvements in self-reported cognitive functioning were limited to abstainers. Baseline cognitive performance did not differentiate those who had abstained from alcohol and relapsed at follow-up.

CONCLUSIONS/IMPORTANCE

Memory and executive functioning impairments were evident among Asian AD patients alongside self-reported cognitive difficulties, thus cognitively demanding psychological interventions may have limited impact during early detoxification. Future studies can build on these findings, with larger samples and measurement of moderating and mediating factors to extend our understanding of how cognitive impairment influences outcome.

When social anxiety co-occurs with substance use: does an impulsive social anxiety subtype explain this unexpected relationship?

Although most conceptualizations of social anxiety emphasise that socially anxious individuals are overtly shy, and utilise avoidant behavioural strategies (e.g., risk-aversion, passivity, and submissiveness), there is tentative support for the existence of an approach-motivated subtype, characterised by risk taking and a greater propensity for substance misuse. It is likely that this subtype may help explain the reported co-occurrence of substance misuse and social anxiety. The current study sought to test via latent class analysis whether an approach-motivated social anxiety subtype could be identified within a community sample. A self-report questionnaire was completed by 351 participants (age: 18-74 years). Two distinct social anxiety subgroups were identified: one characterised by prototypical SAD symptomatology (i.e., behavioural inhibition and risk-avoidance), the second by elevated levels of rash impulsiveness, reward sensitivity, risk-taking and co-occurring substance use problems. The current findings provides support for the existence of a distinct approach-motivated social anxiety subtype and indicates that impulsivity may be critical to understanding the comorbid substance use symptomatology of these individuals.

Modifying the risk associated with an impulsive temperament: a prospective study of drug dependence treatment

The evidence linking the personality trait of impulsivity and substance misuse is well established. Importantly, impulsivity not only predicts substance misuse problems but has an association with duration in treatment, likelihood of completing treatment and time to relapse. Treatment that focuses on increasing awareness and acceptance of thoughts and emotions may potentially address impulsive behaviour and in this respect improve treatment outcomes for substance misuse. The current paper investigated the relationship between the facet of impulsivity that taps into poor inhibitory control and treatment outcome. In addition, there was a specific focus on ascertaining the impact of an increase in awareness and attentional control measured in 144 adult substance users receiving treatment in a residential therapeutic community. Impulsivity predicted poorer treatment outcome (measured as drug use severity). Increases in awareness and acceptance of emotions and thoughts during treatment were related to better outcome although this was not associated with baseline levels of impulsivity. Clinical and theoretical implications are discussed.

Effects of methamphetamine administration on information gathering during probabilistic reasoning in healthy humans

Jumping to conclusions (JTC) during probabilistic reasoning is a cognitive bias repeatedly demonstrated in people with schizophrenia and shown to be associated with delusions. Little is known about the neurochemical basis of probabilistic reasoning. We tested the hypothesis that catecholamines influence data gathering and probabilistic reasoning by administering intravenous methamphetamine, which is known to cause synaptic release of the catecholamines noradrenaline and dopamine, to healthy humans whilst they undertook a probabilistic inference task. Our study used a randomised, double-blind, cross-over design. Seventeen healthy volunteers on three visits were administered either placebo or methamphetamine or methamphetamine preceded by amisulpride. In all three conditions participants performed the "beads" task in which participants decide how much information to gather before making a probabilistic inference, and which measures the cognitive bias towards jumping to conclusions. Psychotic symptoms triggered by methamphetamine were assessed using Comprehensive Assessment of At-Risk Mental States (CAARMS). Methamphetamine induced mild psychotic symptoms, but there was no effect of drug administration on the number of draws to decision (DTD) on the beads task. DTD was a stable trait that was highly correlated within subjects across visits (intra-class correlation coefficients of 0.86 and 0.91 on two versions of the task). The less information was sampled in the placebo condition, the more psychotic-like symptoms the person had after the methamphetamine plus amisulpride condition (p = 0.028). Our results suggest that information gathering during probabilistic reasoning is a stable trait, not easily modified by dopaminergic or noradrenergic modulation.

Risky cannabis use is associated with alexithymia, frontal lobe dysfunction, and impulsivity in young adult cannabis users

Risky or problematic alcohol use by young adults has been found to be associated with factors such as alexithymia, frontal lobe dysfunction, reward sensitivity, and impulsivity. One interpretation is that these factors reflect inherent traits that predispose to risky substance use in general, a notion examined in the present study. Alexithymia, everyday frontal lobe functioning, sensitivity to reward and punishment, and impulsivity were examined in 138 young adult cannabis users who were divided into Low Risk (n = 99) and Risky (n = 39) users according to their Cannabis Use Disorder Identification Test (CUDIT) scores. Risky cannabis use was significantly positively associated with alexithymia, multiple signs of frontal lobe dysfunction in everyday life, and impulsivity. A broader pattern of dysfunction was indicated for risky cannabis use than for risky alcohol use in this sample. Findings are interpreted as likely reflecting not only inherent traits that predispose to risky substance use in general, but also perhaps residual effects of recent heavy cannabis use in the Risky user group. Longitudinal research is needed to disentangle these competing possibilities.

Neurocognition in college-aged daily marijuana users

BACKGROUND

Marijuana is the most commonly used illicit substance in the United States. Use, particularly when it occurs early, has been associated with cognitive impairments in executive functioning, learning, and memory.

METHOD

This study comprehensively measured cognitive ability as well as comorbid psychopathology and substance use history to determine the neurocognitive profile associated with young adult marijuana use. College-aged marijuana users who initiated use prior to age 17 (n = 35) were compared to demographically matched controls (n = 35).

RESULTS

Marijuana users were high functioning, demonstrating comparable IQs to controls and relatively better processing speed. Marijuana users demonstrated relative cognitive impairments in verbal memory, spatial working memory, spatial planning, and motivated decision making. Comorbid use of alcohol, which was heavier in marijuana users, was unexpectedly found to be associated with better performance in some of these areas.

CONCLUSIONS

This study provides additional evidence of neurocognitive impairment in the context of adolescent and young adult marijuana use. Findings are discussed in relation to marijuana's effects on intrinsic motivation and discrete aspects of cognition.

New developments in human neurocognition: clinical, genetic, and brain imaging correlates of impulsivity and compulsivity

Impulsivity and compulsivity represent useful conceptualizations that involve dissociable cognitive functions, which are mediated by neuroanatomically and neurochemically distinct components of cortico-subcortical circuitry. The constructs were historically viewed as diametrically opposed, with impulsivity being associated with risk-seeking and compulsivity with harm-avoidance. However, they are increasingly recognized to be linked by shared neuropsychological mechanisms involving dysfunctional inhibition of thoughts and behaviors. In this article, we selectively review new developments in the investigation of the neurocognition of impulsivity and compulsivity in humans, in order to advance our understanding of the pathophysiology of impulsive, compulsive, and addictive disorders and indicate new directions for research.

Binge drinking, reflection impulsivity, and unplanned sexual behavior: impaired decision-making in young social drinkers

BACKGROUND

The repeated pattern of heavy intoxication followed by withdrawal from alcohol (i.e., "binge drinking") has been found to have substantial adverse effects on prefrontal neural systems associated with decision-making and impulse control. Repeated binge drinking has been linked to risky and unplanned sexual behavior; however few studies have examined the role of impulsivity and related cognitive processes in understanding this association. The aim of this study was to examine the relationship between binge drinking, "reflection impulsivity" (deficits in gathering and evaluating information during decision-making), alcohol-related expectancies, and unplanned sexual behavior in a sample of young social drinkers.

METHODS

Ninety-two university students completed the alcohol use questionnaire (AUQ) to measure alcohol intake and binge drinking. Two groups (low-binge and high-binge) were generated from the AUQ data. The Information Sampling Task (IST) was used to measure reflection impulsivity; the Alcohol Expectancy Questionnaire (AEQ) for alcohol outcome expectancies; and an unplanned sexual behavior questionnaire, which asked about the number of unplanned sexual events.

RESULTS

When compared to the low-binge drinking group, the high-binge drinkers had significantly more unplanned sexual encounters and were impaired on the IST, reflection-impulsivity task. They scored higher on the alcohol expectancy factors of sociability, risk and aggression, negative self-perception, and in particular liquid courage. In a regression analysis, number of unplanned sexual encounters, binge drinking score, and liquid courage were all significantly related.

CONCLUSIONS

These results support the role of binge drinking in reduced impulse control and decision-making deficits. The findings indicate that high-binge drinkers demonstrate impairments on an impulse control task similar to that observed in dependent samples and this may be a factor in understanding the negative behavioral consequences associated with excessive alcohol use.

Measuring "waiting" impulsivity in substance addictions and binge eating disorder in a novel analogue of rodent serial reaction time task

BACKGROUND

Premature responding is a form of motor impulsivity that preclinical evidence has shown to predict compulsive drug seeking but has not yet been studied in humans. We developed a novel translation of the task, based on the rodent 5-choice serial reaction time task, testing premature responding in disorders of drug and natural food rewards.

METHODS

Abstinent alcohol- (n = 30) and methamphetamine-dependent (n = 23) subjects, recreational cannabis users (n = 30), and obese subjects with (n = 30) and without (n = 30) binge eating disorder (BED) were compared with matched healthy volunteers and tested on the premature responding task.

RESULTS

Compared with healthy volunteers, alcohol- and methamphetamine-dependent subjects and cannabis users showed greater premature responding with no differences observed in obese subjects with or without BED. Current smokers exhibited greater premature responding versus ex-smokers and nonsmokers. Alcohol-dependent subjects also had lower motivation for explicit monetary incentives. A Motivation Index correlated negatively with alcohol use and binge eating severity.

CONCLUSIONS

Premature responding on a novel translation of a serial reaction time task was more evident in substance use disorders but not in obese subjects with or without BED. Lower motivation for monetary incentives linked alcohol use and binge eating severity. Our findings add to understanding the relationship between drug and natural food rewards.

The Psychology Experiment Building Language (PEBL) and PEBL Test Battery

BACKGROUND

We briefly describe the Psychology Experiment Building Language (PEBL), an open source software system for designing and running psychological experiments.

NEW METHOD

We describe the PEBL Test Battery, a set of approximately 70 behavioral tests which can be freely used, shared, and modified. Included is a comprehensive set of past research upon which tests in the battery are based.

RESULTS

We report the results of benchmark tests that establish the timing precision of PEBL.

COMPARISON WITH EXISTING METHOD

We consider alternatives to the PEBL system and battery tests.

CONCLUSIONS

We conclude with a discussion of the ethical factors involved in the open source testing movement.

Reflection impulsivity and response inhibition in first-episode psychosis: relationship to cannabis use

BACKGROUND

People with psychosis demonstrate impaired response inhibition on the Stop Signal Task (SST). It is less clear if this impairment extends to reflection impulsivity, a form of impulsivity that has been linked to substance use in non-psychotic samples.

METHOD

We compared 49 patients with first-episode psychosis (FEP) and 30 healthy control participants on two forms of impulsivity measured using the Information Sampling Test (IST) and the SST, along with clinical and IQ assessments. We also compared those patients who used cannabis with those who had either given up or never used.

RESULTS

Patients with FEP had significantly greater impairment in response inhibition but not in reflection impulsivity compared with healthy controls. By contrast, patients who reported current cannabis use demonstrated greater reflection impulsivity than those that had either given up or never used, whereas there were no differences in response inhibition.

CONCLUSIONS

These data suggest that abnormal reflection impulsivity is associated with substance use in psychosis but not psychosis itself ; the opposite relationship may hold for response inhibition.

Effects of cannabis on neurocognitive functioning: recent advances, neurodevelopmental influences, and sex differences

Decades of research have examined the effects of cannabis on neurocognition. Recent advances in this field provide us with a better understanding of how cannabis use influences neurocognition both acutely (during intoxication) and non-acutely (after acute effects subside). Evidence of problems with episodic memory is one of the most consistent findings reported; however, several other neurocognitive domains appear to be adversely affected by cannabis use under various conditions. There is significant variability in findings across studies, thus a discussion of potential moderators is increasingly relevant. The purpose of this review was to 1) provide an update on research of cannabis' acute and non-acute effects on neurocognition, with a focus on findings since 2007 and 2) suggest and discuss how neurodevelopmental issues and sex differences may influence cannabis effects on neurocognition. Finally we discuss how future investigations may lead to better understanding of the complex interplay among cannabis, stages of neurodevelopment, and sex on neurocognitive functioning.

Inhibitory Control Contributes to “Motor”- but not “Cognitive”- Impulsivity

Literature on impulsivity regularly claims inhibitory control deficits underlie impulsive behavior. The current study investigated whether taxing inhibitory control will increase reflection (decision making under conditions of uncertainty), temporal (delay of gratification), and motor impulsivity (behavioral disinhibition). Inhibitory control was challenged, via a random letter generation task presented during responding to three impulsivity measures: the Information Sampling Task (IST), Single Key Impulsivity Paradigm, and the Stop Signal Task (SST). Participants (n = 33) were assigned to the inhibitory control challenging (experimental) condition, or to a control condition in which inhibitory control was not challenged. The SST was affected by the inhibitory control challenge: participants in the experimental condition displayed increased motor impulsivity, evidenced in longer stop signal reaction times (SSRTs) compared to the control group. The manipulation did not affect reflection- or temporal- impulsivity measures. These data support the suggestion that the mechanisms underlying the motor subtype of impulsivity are dissociable from the temporal and reflection subtypes, and that engagement of inhibitory control is not necessary to prevent impulsive decision making.

Impulsivity, attention, memory, and decision-making among adolescent marijuana users

RATIONALE

Marijuana is a popular drug of abuse among adolescents, and they may be uniquely vulnerable to resulting cognitive and behavioral impairments. Previous studies have found impairments among adolescent marijuana users. However, the majority of this research has examined measures individually rather than multiple domains in a single cohesive analysis. This study used a logistic regression model that combines performance on a range of tasks to identify which measures were most altered among adolescent marijuana users.

OBJECTIVES

The purpose of this research was to determine unique associations between adolescent marijuana use and performances on multiple cognitive and behavioral domains (attention, memory, decision-making, and impulsivity) in 14- to 17-year-olds while simultaneously controlling for performances across the measures to determine which measures most strongly distinguish marijuana users from nonusers.

METHODS

Marijuana-using adolescents (n = 45) and controls (n = 48) were tested. Logistic regression analyses were conducted to test for: (1) differences between marijuana users and nonusers on each measure, (2) associations between marijuana use and each measure after controlling for the other measures, and (3) the degree to which (1) and (2) together elucidated differences among marijuana users and nonusers.

RESULTS

Of all the cognitive and behavioral domains tested, impaired short-term recall memory and consequence sensitivity impulsivity were associated with marijuana use after controlling for performances across all measures.

CONCLUSIONS

This study extends previous findings by identifying cognitive and behavioral impairments most strongly associated with adolescent marijuana users. These specific deficits are potential targets of intervention for this at-risk population.

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 nonusing 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 (Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition, 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 than among 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.

Impulsivity differences in recreational cannabis users and binge drinkers in a university population

BACKGROUND

Recreational cannabis use and alcohol binge drinking are the most common drug consumption patterns in young adults. Impulsivity and several psychopathological signs are increased in chronic drug users, but the implications of recreational use are still poorly understood.

METHODS

We evaluated impulsivity, sensation-seeking traits, impulsive decision-making, inhibitory control and possible symptoms of depression, anxiety and psychosis in three groups of young university adults: recreational cannabis users (N=20), alcohol binge drinkers (N=22) and non-drug users (N=26).

RESULTS

The cannabis and binge drinking groups had increased scores for impulsivity and sensation-seeking traits. Both groups also exhibited increased impulsive decision-making on the two-choice task and the Iowa gambling task; however, only the cannabis group was significantly different from the non-drug group regarding inhibitory control (go/no-go and stop tasks). The cannabis and binge drinking groups did not show differences in the psychopathological symptoms evaluated.

CONCLUSIONS

Our observations of this population of non-dependent drug users are consistent with the increased impulsivity traits and behaviors that have been described previously in chronic drug abusers. In this study, compared to no drug use, the recreational use of cannabis was associated with a major dysfunction of the different facets of impulsive behaviors. However, alcohol binge drinking was related only to impulsive decision-making. These results suggest that impulsivity traits and behaviors are present not only in chronic drug abusers but also in recreational drug users. Future work should continue to investigate the long-term effects of these common consumption patterns on various impulsive behaviors and psychopathological symptoms.

Are executive function and impulsivity antipodes? A conceptual reconstruction with special reference to addiction

RATIONALE

Although there is considerable interest in how either executive function (EF) or impulsivity relate to addiction, there is little apparent overlap between these research areas.

OBJECTIVES

The present paper aims to determine if components of these two constructs are conceptual antipodes--widely separated on a shared continuum.

METHODS

EFs and impulsivities were compared and contrasted. Specifically, the definitions of the components of EF and impulsivity, the methods used to measure the various components, the populations of drug users that show deficits in these components, and the neural substrates of these components were compared and contrasted.

RESULTS

Each component of impulsivity had an antipode in EF. EF, however, covered a wider range of phenomena, including compulsivity.

CONCLUSIONS

Impulsivity functions as an antipode of certain components of EF. Recognition of the relationship between EF and impulsivity may inform the scientific inquiry of behavioral problems such as addiction. Other theoretical implications are discussed.

Dopamine, serotonin and impulsivity

Impulsive people have a strong urge to act without thinking. It is sometimes regarded as a positive trait but rash impulsiveness is also widely present in clinical disorders such as attention deficit hyperactivity disorder (ADHD), drug dependence, mania, and antisocial behaviour. Contemporary research has begun to make major inroads into unravelling the brain mechanisms underlying impulsive behaviour with a prominent focus on the limbic cortico-striatal systems. With this progress has come the understanding that impulsivity is a multi-faceted behavioural trait involving neurally and psychologically diverse elements. We discuss the significance of this heterogeneity for clinical disorders expressing impulsive behaviour and the pivotal contribution made by the brain dopamine and serotonin systems in the aetiology and treatment of behavioural syndromes expressing impulsive symptoms.

Reflection impulsivity in adolescent cannabis users: a comparison with alcohol-using and non-substance-using adolescents

RATIONALE

Reflection impulsivity-a failure to gather and evaluate information before making a decision-is a critical component of risk-taking and substance use behaviours, which are highly prevalent during adolescence.

OBJECTIVES AND METHODS

The Information Sampling Test was used to assess reflection impulsivity in 175 adolescents (mean age 18.3, range 16.5-20; 55% female)-48 cannabis users (2.3 years use, 10.8 days/month), 65 alcohol users, and 62 non-substance-using controls-recruited from a longitudinal cohort and from the general community and matched for education and IQ. Cannabis and alcohol users were matched on levels of alcohol consumption.

RESULTS

Cannabis users sampled to the lowest degree of certainty before making a decision on the task. Group differences remained significant after controlling for relevant substance use and clinical confounds (e.g., anxiety, depressive symptoms, alcohol, and ecstasy use). Poor performance on multiple IST indices was associated with an earlier age of onset of regular cannabis use and greater duration of exposure to cannabis, after controlling for recent use. Alcohol users did not differ from controls on any IST measure.

CONCLUSIONS

Exposure to cannabis during adolescence is associated with increased risky and impulsive decision making, with users adopting strategies with higher levels of uncertainty and inefficient utilisation of information. The young cannabis users did show sensitivity to losses, suggesting that greater impulsivity early in their drug using career is more evident when there is a lack of negative consequences. This provides a window of opportunity for intervention before the onset of cannabis dependence.

The effects of acute tryptophan depletion on costly information sampling: impulsivity or aversive processing?

RATIONALE

The neurotransmitter serotonin (5-HT) has been implicated in both aversive processing and impulsivity. Reconciling these accounts, recent studies have demonstrated that 5-HT is important for punishment-induced behavioural inhibition. These studies focused on situations where actions lead directly to punishments. However, decision-making often involves making tradeoffs between small 'local' costs and larger 'global' losses.

OBJECTIVE

We aimed to distinguish whether 5-HT promotes avoidance of local losses, global losses, or both, in contrast to an overall effect on reflection impulsivity. We further examined the influence of individual differences in sub-clinical depression, anxiety and impulsivity on global and local loss avoidance.

METHODS

Healthy volunteers (N = 21) underwent an acute tryptophan depletion procedure in a double-blind, placebo-controlled crossover design. We measured global and local loss avoidance in a decision-making task where subjects could sample information at a small cost to avoid making incorrect decisions, which resulted in large losses.

RESULTS

Tryptophan depletion removed the suppressive effects of small local costs on information sampling behaviour. Sub-clinical depressive symptoms produced effects on information sampling similar to (but independent from) those of tryptophan depletion. Dispositional anxiety was related to global loss avoidance. However, trait impulsivity was unrelated to information sampling.

CONCLUSIONS

The current findings are consistent with recent theoretical work that characterises 5-HT as pruning a tree of potential decisions, eliminating options expected to lead to aversive outcomes. Our results extend this account by proposing that 5-HT promotes reflexive avoidance of relatively immediate aversive outcomes, potentially at the expense of more globally construed future losses.

Cannabinoid CB1 receptor activation mediates the opposing effects of amphetamine on impulsive action and impulsive choice

It is well known that acute challenges with psychostimulants such as amphetamine affect impulsive behavior. We here studied the pharmacology underlying the effects of amphetamine in two rat models of impulsivity, the 5-choice serial reaction time task (5-CSRTT) and the delayed reward task (DRT), providing measures of inhibitory control, an aspect of impulsive action, and impulsive choice, respectively. We focused on the role of cannabinoid CB1 receptor activation in amphetamine-induced impulsivity as there is evidence that acute challenges with psychostimulants activate the endogenous cannabinoid system, and CB1 receptor activity modulates impulsivity in both rodents and humans. Results showed that pretreatment with either the CB1 receptor antagonist/inverse agonist SR141716A or the neutral CB1 receptor antagonist O-2050 dose-dependently improved baseline inhibitory control in the 5-CSRTT. Moreover, both compounds similarly attenuated amphetamine-induced inhibitory control deficits, suggesting that CB1 receptor activation by endogenously released cannabinoids mediates this aspect of impulsive action. Direct CB1 receptor activation by Δ9-Tetrahydrocannabinol (Δ9-THC) did, however, not affect inhibitory control. Although neither SR141716A nor O-2050 affected baseline impulsive choice in the DRT, both ligands completely prevented amphetamine-induced reductions in impulsive decision making, indicating that CB1 receptor activity may decrease this form of impulsivity. Indeed, acute Δ9-THC was found to reduce impulsive choice in a CB1 receptor-dependent way. Together, these results indicate an important, though complex role for cannabinoid CB1 receptor activity in the regulation of impulsive action and impulsive choice as well as the opposite effects amphetamine has on both forms of impulsive behavior.

Dopamine D2/D3 receptor availability and venturesomeness

The construct of impulsivity is considered as a major trait of personality. There is growing evidence that the mesolimbic dopamine system plays an important role in the modulation of impulsivity and venturesomeness, the two key components within the impulsivity-construct. The aim of the present study was to explore an association between trait impulsivity measured with self-assessment and the dopaminergic neurotransmission as measured by positron emission tomography (PET) in a cohort of healthy male subjects. In vivo D2/D3 receptor availability was determined with [(18)F]fallypride PET in 18 non-smoking healthy subjects. The character trait impulsivity was measured using the Impulsiveness-Venturesomeness-Empathy questionnaire (I7). Image processing and statistical analysis was performed on a voxel-by-voxel basis using statistical parametric mapping (SPM) software. The I7 subscale venturesomeness correlated positively with the D2/D3 receptor availability within the left temporal cortex and the thalamus. Measures on the I7 subscale impulsiveness and empathy did not correlate with the D2/D3 receptor availability in any brain region investigated. Our results suggest the involvement of extrastriatal dopaminergic neurotransmission in venturesomeness, a component of impulsivity.

Impulsiveness and venturesomeness in German smokers

INTRODUCTION

Cigarette smoking is a behavior, which is influenced by genetic, demographic, and psychological factors. A large body of research has examined the association of cigarette smoking variables with individual differences in personality traits. The aim of the current study was to replicate the findings of higher self-reported impulsivity in smokers compared with never-smokers in a German sample using Eysenck´s construct of impulsivity. Furthermore, it was intended to further the knowledge about associations between different self-reported impulsivity components and different smoking variables.

METHODS

We used the Impulsiveness-Venturesomeness-Empathy questionnaire (I7) to measure self-reported impulsiveness and venturesomeness and the Temperament and Character Inventory (TCI) to measure novelty seeking (NS) in a sample of 82 nicotine-dependent smokers and 119 never-smokers.

RESULTS

Smokers scored higher on impulsiveness, venturesomeness, and NS than never-smokers independent of age, gender, and years of education. We found a significant association between venturesomeness, impulsiveness and smoking status in daily smokers.

CONCLUSIONS

In summary, this study provides evidence that impulsiveness and venturesomeness as well as the novelty-seeking subscale extravagance are significantly associated with smoking status in a German sample of female and male smokers compared with never-smokers.

Residual neurocognitive features of long-term ecstasy users with minimal exposure to other drugs

AIMS

In field studies assessing cognitive function in illicit ecstasy users, there are several frequent confounding factors that might plausibly bias the findings toward an overestimate of ecstasy-induced neurocognitive toxicity. We designed an investigation seeking to minimize these possible sources of bias.

DESIGN

We compared illicit ecstasy users and non-users while (1) excluding individuals with significant life-time exposure to other illicit drugs or alcohol; (2) requiring that all participants be members of the 'rave' subculture; and (3) testing all participants with breath, urine and hair samples at the time of evaluation to exclude possible surreptitious substance use. We compared groups with adjustment for age, gender, race/ethnicity, family-of-origin variables and childhood history of conduct disorder and attention deficit hyperactivity disorder. We provide significance levels without correction for multiple comparisons.

SETTING

Field study.

PARTICIPANTS

Fifty-two illicit ecstasy users and 59 non-users, aged 18-45 years.

MEASUREMENTS

Battery of 15 neuropsychological tests tapping a range of cognitive functions.

FINDINGS

We found little evidence of decreased cognitive performance in ecstasy users, save for poorer strategic self-regulation, possibly reflecting increased impulsivity. However, this finding might have reflected a pre-morbid attribute of ecstasy users, rather than a residual neurotoxic effect of the drug.

CONCLUSIONS

In a study designed to minimize limitations found in many prior investigations, we failed to demonstrate marked residual cognitive effects in ecstasy users. This finding contrasts with many previous findings-including our own-and emphasizes the need for continued caution in interpreting field studies of cognitive function in illicit ecstasy users.

Neural correlates of choice behavior related to impulsivity and venturesomeness

Impulsivity has been associated with several psychiatric disorders including drug addiction and gambling. Impulsive subjects typically have a preference for short-term over long-term rewards and make risky choices. This study used functional magnetic resonance imaging (fMRI) to investigate the neural correlates of self-rated impulsivity and venturesomeness during tasks involving delayed and risky choice. A broader sampling approach was taken by recruiting participants with behaviors that have been linked to impulsivity (gambling N=15, and recreational drug use N=10) and those without these behaviors (N=9). Selection between delayed or probabilistic rewards was associated with activation in fronto-parietal regions in line with previous research. When selecting between delayed rewards, activity within the pregenual anterior cingulate cortex and ventrolateral prefrontal cortex correlated positively with impulsivity scores while activity within the orbitofrontal cortex, subgenual anterior cingulate cortex and caudate correlated positively with venturesomeness scores. Selection between probabilistic rewards revealed no correlation between scores and regional activations. The results from this study provide targets for future research investigating the neural substrates of impulsivity. They also provide targets for the further investigation into the pathophysiology of addiction and impulse-control disorders.