Dimensions of impulsive behavior in adolescent smokers and nonsmokers

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.

Laboratory method to induce state boredom increases impulsive choice in people who use cocaine and controls

Background: Impulsive choice is associated with both cocaine use and relapse. Little is known about the influence of transient states on impulsive choice in people who use cocaine (PWUC).Objective: This study investigated the direct effects of induced boredom on impulsive choice (i.e., temporal discounting) in PWUC relative to well-matched community controls.Methods: Forty-one PWUC (≥1× cocaine use in past 3 months; 7 females) and 38 demographically matched controls (5 females) underwent two experimental conditions in counterbalanced order. Temporal discounting was assessed immediately after a standardized boredom induction task (peg-turning) and a self-selected video watched for the same duration (non-boredom). Subjective mood state and perceived task characteristics were assessed at baseline, during experimental manipulations, and after the choice task.Results: PWUC and controls were well matched on sex, age, and socioeconomic status. Groups were also similar in reported use of drugs other than cocaine, except for recent cigarette and alcohol use (PWUC > controls). As expected, peg-turning increased boredom in the sample overall, with higher boredom reported during peg-turning than the video (p < .001, η2p = .20). Participants overall exhibited greater impulsive choice after boredom than non-boredom (p = .028, η2p = .07), with no preferential effects in PWUC (p > .05, BF01 = 2.9).Conclusion: Experimentally induced boredom increased state impulsivity irrespective of cocaine use status - in PWUC and carefully matched controls - suggesting a broad link between boredom and impulsive choice. This is the first study to show that transient boredom directly increases impulsive choice. Data support a viable laboratory method to further parse the effects of boredom on impulsive choice.

Diagnostic group differences and exploratory sex differences in intrinsic connectivity during fMRI Stroop in individuals with and without cocaine use disorder

BACKGROUND

Sex-/gender-related differences in cognitive control and how they relate to addictions may inform novel treatment options. Cognitive control, including Stroop performance, has been linked to addictions and treatment outcomes. The extent to which women and men with cocaine use disorder (CUD) show brain and behavioral differences relating to Stroop performance has not been previously studied. We examined sex-related differences in Stroop-related brain connectivity in female and male CUD and healthy-comparison (HC) subjects.

METHODS

40 individuals with CUD (20 female) and 40 HC (20 female) subjects matched on age, race, and ethnicity completed an fMRI Stroop task. Intrinsic connectivity distribution (ICD) and mean-adjusted ICD analyses were conducted to identify differences related to sex and diagnostic group. Stroop task performance was also considered.

RESULTS

Behavioral results confirmed a Stroop effect. A main effect of diagnostic group indicated that the CUD versus HC group showed lower connectivity in the prefrontal cortex, frontal gyrus, cingulate gyrus, precuneus, cerebellum, and somatosensory, visual, and auditory areas. An exploratory main effect of sex suggested that males may show relatively lower connectivity than females in the cerebellum and brainstem, although connectivity was largely similar across sexes.

CONCLUSIONS

Intrinsic connectivity during cognitive control varied by diagnostic group and possibly by sex. The findings suggest that interventions targeting cognitive control in CUD should consider sex.

Genetic variation in fatty acid amide hydrolase (FAAH): Associations with early drinking and smoking behaviors

BACKGROUND

The endocannabinoid system is implicated in psychiatric disorders and drug dependence. Within this system, fatty acid amide hydrolase (FAAH) metabolizes endocannabinoids. Individuals with A-group genotypes (C/A or A/A) of a common FAAH variant (rs324420; C > A; Pro129Thr) have slower enzymatic activity compared to C-group individuals (C/C genotype). Slow FAAH activity is differentially associated with alcohol and nicotine use.

METHODS

Among European-ancestry participants in the NDIT study (n = 249-607), genotype associations with past-year binge drinking in young adults were estimated in logistic regression models. In adolescents, hazard ratios (HR) were estimated from Cox proportional hazards models to assess the FAAH genotype group association with time to drinking initiation and attaining drinking frequency outcomes. HR were also used to assess genotype effect on time to smoking initiation and attaining early smoking milestones (e.g., first inhalation, ICD-10 dependence).

RESULTS

Compared to those in the C-group, those in the A-group had higher odds of binge drinking at ages 20 (Odds ratio (OR) = 2.16, 95 % CI 1.36-3.42) and 30 (OR = 1.61, 95 % CI 1.10-2.36). Time to initiation of drinking and daily drinking was faster in adolescents in the A-group (HR = 1.39, 95 % CI 1.09-1.77 and HR = 2.24, 95 % CI 1.05-4.76, respectively). Time to smoking initiation was faster in the A-group (HR = 1.20, 95 % CI 1.04-1.39); however, time to smoking milestones among adolescent smokers was not consistently different for the A- versus C-groups (HR = 0.43 to 1.13).

CONCLUSIONS

Slow FAAH activity (A-group) was associated with greater risks for binge drinking, drinking initiation and escalation, and cigarette smoking initiation, but had little impact on the escalation in cigarette smoking behaviors.

The Effects of Cognitive-Affective Switching With Unpredictable Cues in Adults and Adolescents and Their Relation to "Cool" Executive Functioning and Emotion Regulation

The impact of emotion on executive functioning is gaining interest. It has led to the differentiation of "cool" Executive Functioning (EF) processes, such as cognitive flexibility, and "hot" EF processes, such as affective flexibility. But how does affective flexibility, the ability to switch between cognitive and affective information, vary as a function of age and sex? How does this construct relate to "cool" executive functioning and cognitive-emotion regulation processes? In this study, 266 participants, including 91 adolescents (M = 16.08, SD = 1.42 years old) and 175 adults (M = 25.69, SD = 2.17 years old), completed a cognitive-affective switching task with specific (as opposed to general) unpredictable switches, as well as measures of inhibition, attention, and cognitive-emotion coping strategies. We expected cognitive to affective switching to be more costly than affective to cognitive switching in females versus males, as well as higher switch costs in adolescents. Using linear mixed modelling, we analysed the effect of age, sex, and types of switching on reaction time. Results show that adolescents are slower switchers than adults, and demonstrate that females, although faster switchers than males, are slower when switching from cognitive to affective content than when they are switching from affective to cognitive content. Multiple regression analyses revealed age-specific associations between cognitive-affective switching and inhibition. These results converge with reported developmental and gender specificities in EF and emotion processing, respectively. Additionally, affective flexibility could relate to differences in vigilance and inhibition.

Sex Differences in Substance Use Disorders: A Neurobiological Perspective

Clinical studies provide fundamental knowledge of substance use behaviors (substance of abuse, patterns of use, relapse rates). The combination of neuroimaging approaches reveal correlation between substance use disorder (SUD) and changes in neural structure, function, and neurotransmission. Here, we review these advances, placing special emphasis on sex specific findings from structural neuroimaging studies of those dependent on alcohol, nicotine, cannabis, psychostimulants, or opioids. Recent clinical studies in SUD analyzing sex differences reveal neurobiological changes that are differentially impacted in common reward processing regions such as the striatum, hippocampus, amygdala, insula, and corpus collosum. We reflect on the contribution of sex hormones, period of drug use and abstinence, and the potential impact of these factors on the interpretation of the reported findings. With the overall recognition that SUD impacts the brains of females and males differentially, it is of fundamental importance that future research is designed with sex as a variable of study in this field. Improved understanding of neurobiological changes in males and females in SUD will advance knowledge underlying sex-specific susceptibility and the neurobiological impact in these disorders. Together these findings will inform future treatments that are tailor designed for improved efficacy in females and males with SUD.

Associations of childhood executive control with adolescent cigarette and E-cigarette use: Tests of moderation by poverty level

BACKGROUND

Adolescent cigarette smoking has continued to decline, whereas electronic cigarette (e-cigarette) use has increased dramatically among youth. Nicotine use in any form, even at low levels, during adolescence can have adverse consequences, particularly for low-income individuals. To elucidate potential early intervention targets, this study examined childhood executive control (EC), a set of cognitive processes for directing attention and behavior, in relation to adolescent cigarette and e-cigarette onset, testing for differential prediction by poverty level.

METHOD

Participants were 313 children (51% female, 64% European American) recruited in a small city in the Midwestern United States beginning in 2006 and then followed into adolescence between ages 14 and 16 years. EC was measured in the laboratory with performance-based tasks when children were age 5 years, 3 months. Self-reports of cigarette onset and e-cigarette onset were obtained in adolescence (M^age = 15.65 years). Overall, 24% of the sample was at or below the poverty line.

RESULTS

Cigarette onset was higher in the poverty group (17%) than in the non-poverty (8%) group, but e-cigarette onset did not differ by poverty level (36% poverty versus 38% non-poverty). Multiple group structural equation modeling revealed a statistically significant group difference such that EC ability was a significant negative predictor of e-cigarette onset for poverty but not for non-poverty youth. A similar group difference was evident as a trend for cigarette onset.

CONCLUSIONS

Because EC has been shown to be modifiable, early interventions to improve EC for children living in poverty might help prevent adolescent e-cigarette onset.

5HT-2C agonist lorcaserin decreases cannabis self-administration in daily cannabis smokers

There are no FDA-approved treatments for cannabis use disorder (CUD). Preclinical research has shown that the 5HT-2C agonist lorcaserin attenuates cue-induced reinstatement of THC seeking and self-administration. The goal of this placebo-controlled, counterbalanced, within-subject human laboratory study was to examine lorcaserin's effects on cannabis intoxication and self-administration. Lorcaserin (10 mg BID) was administered during one of two 13-day inpatient phases and placebo during the other; each phase was separated by ≥7 days of washout. Inpatient phases comprised (1) standardized cannabis administration (7.0% THC) at no financial cost (intoxication), counterbalanced with (2) the option to self-administer cannabis following either 0 or 3 days of abstinence. Cognitive task performance, food intake, subjective ratings of drug effects, objective/subjective sleep measures, and tobacco cigarette use were also assessed. Fifteen normal-weight, daily cannabis users (4F, 11M) not seeking treatment for CUD completed the study. Lorcaserin significantly reduced cannabis self-administration following 0 and 3 days of cannabis abstinence and also reduced craving for cannabis during abstinence. Lorcaserin produced small but significant increases in positive cannabis ratings and body weight relative to placebo. Lorcaserin also reduced tobacco cigarette smoking on days of cannabis administration relative to placebo. During abstinence, subjective but not objective measures of sleep quality worsened during lorcaserin maintenance. Overall, lorcaserin's ability to decrease drug taking and cannabis craving in nontreatment-seeking cannabis users supports further investigation of 5HT-2C agonists as potential pharmacotherapies for CUD.

Sex-specific effects of cigarette smoking on caudate and amygdala volume and resting-state functional connectivity

Recent studies have demonstrated sex-specific differences in etiology, course and brain dysfunction that are associated with cigarette smoking. However, little is known about sex-specific differences in subcortical structure and function. In this study, structural and resting-state functional magnetic resonance imaging (fMRI) data were collected from 60 cigarette smokers (25 females) and 67 nonsmokers (28 females). The structural MRI was applied to identify deficits in sex-specific subcortical volume. Using resting-state fMRI, sex-related alterations in resting-state functional connectivity (rsFC) were investigated in subcortical nuclei with volume deficits as seed regions. Compared to nonsmokers, male but not female smokers demonstrated a significantly smaller volume in the left caudate, while female but not male smokers showed a smaller volume in the right amygdala. Resting-state FC analysis revealed that male but not female smokers had increased rsFC between the left caudate and the left prefrontal cortex but decreased rsFC within the bilateral caudate and between the right amygdala and right orbitofrontal cortex (OFC). Furthermore, the right amygdala volume was negatively correlated with the impulsivity score in female but not male smokers. The rsFC of the right amygdala-OFC circuit was negatively associated with the craving score in male but not female smokers. These findings indicate that cigarette smoking may have differential effects on the caudate and amygdala volumes as well as rsFC between men and women, contributing to our knowledge of sex-specific effects of nicotine addiction. Such sex-specific differences in subcortical structure and function may provide a methodological framework for the development of sex-specific relapse prevention therapies.

Symptomatological Variants and Related Clinical Features in Adult Attention Deficit Hyperactive Disorder

A large amount of the current literature has focused on the characteristic symptoms of attention deficit hyperactivity disorder (ADHD) in children and adolescents. In contrast, less attention has been devoted to ADHD clinical subtypes in adult patients. We evaluated 164 consecutive adult ADHD (A-ADHD) outpatients using DSM-5 criteria and many specific rating scales and questionnaires. A principal component factor analysis was performed on clinical and symptomatological variables to describe potential clinical variants. We sought to determine different A-ADHD variants focusing on demographic and clinical features. A four-factor solution was identified, and patients were clustered, according to their z-score, in 4 subgroups. The first was marked out by Emotional Dysregulation (ED), the second by Substance Use (SU), the third by Core-ADHD Symptoms (Co-ADHD) and the fourth by Positive Emotionality (PE). Predominantly ED patients showed worse overall function, early treatment with antidepressants and a greater presence of borderline personality disorder than predominantly Co-ADHD patients. Predominantly SU patients reported high rates of bipolar disorder and severe general psychopathology. The PE factor was related to hyperthymic temperament and hypomania and showed a higher level of functioning. Females with A-ADHD showed a lower risk of being included in SU, and A-ADHD patients with co-occurring delayed sleep phase had less risk of being included in the SU factor than the prevailing Co-ADHD group. Our empirically based description of four clinical A-ADHD variants shows several aspects beyond the definition given by the DSM-5 diagnostic criteria.

The relationship between impulsivity and shame and guilt proneness on the prediction of internalizing and externalizing behaviors

Shame and guilt are responses to moral transgressions that are characterized by negative self-evaluations and negative behavioral-evaluations, respectively. Previous research has found shame to be the more maladaptive of these “self-conscious” emotions due to its association with various health-risk behaviors. In the current study, undergraduate participants (n = 199) from a large, public university completed behavioral and self-report measures of impulsivity, shame and guilt-proneness, and behavioral tendencies. Exploratory factor analysis and mediation models were used to determine if shame and/or guilt-proneness significantly mediate the relationship between impulsivity and internalized/externalized problems. Findings demonstrate that impulsivity and shame proneness both positively predict internalized and externalized problem behavior, but indirect effects of shame and guilt are not significant. These findings indicate that shame and guilt do not reliably mediate the relationship between impulsivity and problem behavior, but they do support previous findings on the maladaptive nature of impulsivity and shame. Implications for the protective nature of guilt proneness are also discussed.

Are relationships between impulsivity and depressive symptoms in adolescents sex-dependent?

Introduction

Both depressive symptomology and impulsivity are common during adolescence and are associated with various negative life outcomes. The potential sex-dependent nature of relationships between these constructs needs further exploration in order to understand their complexities. This cross-sectional study examined how levels of these constructs may differ by sex. Additionally, we investigated whether sex moderates relationships between adolescents' depression symptoms and different facets of impulsivity.

Methods

156 adolescents (M_age = 17.37, SD = 1.91, 59% female) completed self-report measures of their demographics, depression symptoms, and impulsivity. Multiple Analysis of Covariance (MANCOVA) assessed mean differences in depression symptoms and impulsivity by sex and race/ethnicity. Moderation analyses examined how sex may indirectly affect relationships between depression symptoms to predict attentional, motor, and non-planning impulsivity facets, as well as overall trait impulsivity.

Results

Correlations between depression symptoms and impulsivity scores were significant. Baseline depression symptoms were significantly higher among females (M = 9.53) compared to males (M = 6.68). Moderation effects of sex were not significant for attentional, motor, or overall trait impulsivity. However, sex moderated relations between depression symptoms and non-planning impulsivity, such that adolescent males showed higher levels of non-planning impulsivity when they reported high levels of depressive symptoms (B = .32, p < .01). This relationship was not significant for females.

Conclusions

While adolescent females may be more prone to depression, adolescent males may be more likely to experience non-planning impulsivity when experiencing symptoms of depression. The results of this study extend the literature regarding sex differences in vulnerabilities between these constructs. We suggest interventions targeting non-planning impulsivity may be especially salient for adolescent males reporting high levels of depressive symptoms.

UPPS-P impulsive personality traits and adolescent cigarette smoking: A meta-analysis

BACKGROUND

Adolescence is a critical developmental period in the trajectory of nicotine dependence, highlighting the need for a greater understanding of the modifiable risk factors. An extensive body of research has found that trait impulsivity is associated with higher levels of adolescent smoking; however, findings have been mixed. The present study aimed to synthesise existing literature to determine the strength and nature of the relationship between the UPPS-P impulsive traits and both adolescent cigarette consumption and nicotine dependence.

METHODS

Fifty-one studies were meta-analysed using a random effects model to determine the association between each UPPS-P impulsive trait and both adolescent cigarette consumption and nicotine dependence. Age, gender, ethnicity and sample type were examined as potential moderators.

RESULTS

Cigarette consumption was positively associated with each UPPS-P impulsive trait (r's ranging from 0.17-0.20). There were an insufficient number of studies to meta-analyse the association between nicotine dependence and the UPPS-P impulsive traits. There were no significant moderation effects of age, gender, ethnicity or sample type.

CONCLUSIONS

Findings suggest that each UPPS-P impulsive trait shares similar associations with adolescent cigarette consumption. Additional studies are needed to determine the relationship between adolescent nicotine dependence and impulsivity. As most adult smokers initiate during adolescence, targeting these impulsive traits via novel prevention and intervention strategies may assist in reducing the prevalence of smoking.

Dimensions of impulsive behavior: Predicting contingency management treatment outcomes for adolescent smokers

BACKGROUND

Behavioral measures of impulsive behavior include the dimensions of behavioral disinhibition, decision-making, and lapses of attention. These behaviors are associated with a range of risky activities during adolescence, including cigarette smoking; however, few studies have evaluated their associations with tobacco treatment outcomes. The current study examined the relationship between impulsive behavior and contingency management treatment outcomes for adolescent smokers.

METHODS

Data from two contingency management smoking cessation trials were combined (N = 189 adolescents). Participants provided breath carbon monoxide (CO) samples with incentives delivered contingent (i.e., active treatment [AT] condition) or non-contingent (i.e., control treatment [CT] condition) on CO level. Dimensions of impulsive behavior were assessed pre- and post-treatment using the Go/Stop Task, a measure of delay discounting, a continuous performance task, while self-reported impulsivity was assessed with the Barratt Impulsiveness Scale-Adolescent. Relationships between impulsive behavior and treatment outcomes (efficacy and adherence) were assessed using linear mixed effects models.

RESULTS

Participants in the AT condition had significantly lower program CO levels at each treatment phase. Delay discounting in the AT condition predicted CO levels, with those discounting the most lowering their breath CO levels the least. Delay discounting also predicted program adherence across both conditions.

CONCLUSIONS

Delay discounting may be the most relevant dimension of impulsive behavior to predict outcomes for adolescent smokers completing CM programs, both in terms of successful reductions in smoking and program adherence. Suggestions are made to reduce the effects of delay discounting for adolescent smokers using this treatment approach.

Time-discounting and tobacco smoking: a systematic review and network analysis

Background: Tobacco smoking harms health, so why do people smoke and fail to quit? An explanation originating in behavioural economics suggests a role for time-discounting, which describes how the value of a reward, such as better health, decreases with delay to its receipt. A large number of studies test the relationship of time-discounting with tobacco outcomes but the temporal pattern of this relationship and its variation according to measurement methods remain unclear. We review the association between time-discounting and smoking across (i) the life course, from initiation to cessation, and (ii) diverse discount measures.

Methods: We identified 69 relevant studies in Web of Science and PubMed. We synthesized findings across methodologies and evaluated discount measures, study quality and cross-disciplinary fertilization.

Results: In 44 out of 54 studies, smokers more greatly discounted the future than non-smokers and, in longitudinal studies, higher discounting predicted future smoking. Smokers with lower time-discount rates achieved higher quit rates. Findings were consistent across studies measuring discount rates using hypothetical monetary or cigarette reward scenarios. The methodological quality of the majority of studies was rated as ‘moderate’ and co-citation analysis revealed an isolation of economics journals and a dearth of studies in public health.

Conclusion: There is moderate yet consistent evidence that high time-discounting is a risk factor for smoking and unsuccessful cessation. Policy scenarios assuming a flat rate of population discounting may inadequately capture smokers’ perceptions of costs and benefits.

Does Pain Affect Preference? The Effect of Tonic Laboratory Pain on Discounting of Delayed Rewards

Chronic pain patients show elevated risk behavior on decision-making tasks, as well as increased health risk behaviors (eg, smoking, prescription opioid abuse). Determining pain's effect on underlying cognitive processes that are associated with risk behavior is confounded by comorbidities linked with chronic pain, including depression, anxiety, and substance abuse. Therefore, to understand pain's effect on delay discounting, a behavioral process assessing the extent to which outcomes are devalued as a function of their delay, the present study evaluated the effect of laboratory pain on delay discounting in healthy young adults (N = 85). Using a mixed factorial design, pain (topical capsaicin and warmth) as well as active control (warmth) groups completed a delay discounting task before and during exposure to their respective manipulations. Whereas the pain condition had no effect on delay discounting, participants' pain intensity, unpleasantness, and pain-induced negative valence were associated with less discounting of delayed rewards. However, the effects were very small.

PERSPECTIVE

The results suggest that experimental pain may not increase delay discounting, rather sensitivity to pain predicts a very small decrease in discounting of delayed rewards. Although the results are limited to healthy volunteers, this experimental approach allows us to examine the relationship between pain and delay discounting in a controlled manner. Better understanding of pain-related decision-making may lead to improved treatment of health risk behaviors for individuals experiencing pain.

Pharmacological investigations of a yohimbine-impulsivity interaction in rats

Both impulsivity and stress are risk factors for substance abuse, but it is not clear how these two processes interact to alter susceptibility for the disorder. The aim of this project was to examine the pharmacology of a stress-impulsivity interaction in rats. To do so, we tested the effects of yohimbine on impulsive action and then assessed whether behavioural changes could be reduced by antagonists at different receptor subtypes. Male Long-Evans rats were injected with various doses of yohimbine (0-5.0 mg/kg) before testing in the response-inhibition task. In subsequent experiments, yohimbine (2.5 mg/kg) was injected following pretreatment with the following receptor antagonists: corticotropin-releasing factor receptor 1, antalarmin (0-20 mg/kg); glucocorticoid, mifepristone (0-30 mg/kg); noradrenergic (NA) α1, prazosin (0-2 mg/kg); NA α2, guanfacine (0-0.5 mg/kg); NA β2, propranolol (0.5-2.0 mg/kg); dopamine D1/5, SCH 39166 (0-0.0625 mg/kg); μ opioid, naloxone (0-2 mg/kg); or 5-HT2A, M100907 (0.005-0.05 mg/kg). In all experiments, impulsive action was measured as increased premature responding. Yohimbine dose dependently increased impulsive action, but the effect was not reversed by antagonist pretreatment. None of the drugs altered any other behavioural measure. We conclude that stress-impulsivity interactions are likely mediated by a synergy of multiple neurotransmitter systems.

Sex-specific attenuation of impulsive action by progesterone in a go/no-go task for cocaine in rats

RATIONALE

Previous work indicated that progesterone (PRO) reduced impulsive choice for cocaine in female but not male rats (Smethells et al. Psychopharmacology 233:2999-3008, 2016). Impulsive action, typically measured by responding for a reinforcer during a signaled period of nonavailability of natural reinforcers, predicts initiation and escalation of drug use in animals and humans. The present study examined impulsive action for cocaine using PRO in male and female rats trained on a go/no-go task.

OBJECTIVE

Rats were trained on a go/no-go task to respond for cocaine infusions (0.4 mg/kg/inf). During the "go" component, responding was reinforced on a VI 30-s schedule, whereas during the "no-go" component, withholding a response was reinforced on a differential reinforcement of other behavior (DRO) 30-s schedule. A response during the no-go component resets the DRO timer and served as a measure of impulsive action. After baseline responding was established, rats were pretreated with vehicle (VEH) or PRO (0.5 mg/kg), and DRO resets and responding during the go component for cocaine were compared in males vs. females.

RESULTS

DRO resets were significantly lower following PRO treatment compared to VEH in female, but not male, rats. Response rates and overall infusions during the go component were not significantly altered by PRO in either females or males.

CONCLUSION

Treatment with PRO resulted in a sex-specific reduction in impulsive action for cocaine, while not affecting cocaine self-administration.

Early age of e-cigarette use onset mediates the association between impulsivity and e-cigarette use frequency in youth

BACKGROUND

Identifying risk factors for youth e-cigarette use is critical, given high rates of e-cigarette use and unknown health effects of long-term use. The current study examined whether an early age of onset of e-cigarette use mediates the association between impulsivity and e-cigarette frequency.

METHODS

Cross-sectional survey data of e-cigarette users (n=927) were collected from 8 high schools in southeastern Connecticut. The sample was 44.7% female (mean age 16.2 [SD=1.2], mean age of e-cigarette onset 14.7 [SD=1.6]). Two domains of self-reported, trait impulsivity were assessed using the abbreviated Barratt Impulsiveness Scale: impaired self-regulation (e.g., problems with concentration or self-control) and behavioral impulsivity (e.g., doing things without thinking). Mediation was tested with Mplus, and the model included school as a cluster variable and controlled for covariates related to e-cigarette use (i.e., sex, age, race, peer use, and other tobacco products ever tried).

RESULTS

The hypothesized mediation was supported for both domains of impulsivity (impaired self-regulation a₁b=0.09, SE=0.02, 95%CI [0.03-0.14], p=.002; behavioral impulsivity a₂b=0.07, SE=0.03, 95%CI [.01-.14], p=0.03). Specifically, impaired self-regulation (B=-0.33, SE=0.06, p<0.001) and behavioral impulsivity (B=-0.26, SE=0.11, p=0.02) predicted trying e-cigarettes at an earlier age, and earlier initiation was associated with more days of e-cigarette use in the past month (B=-0.28, SE=0.08, p<0.001).

CONCLUSIONS

Adolescents who endorse aspects of impulsivity, such as acting without thinking, are at greater risk for more frequent e-cigarette use through an early age of e-cigarette initiation. Further research is needed to evaluate these relationships longitudinally and to develop targeted e-cigarette interventions for impulsive youth.

A longitudinal study of the reciprocal relationship between ever smoking and urgency in early adolescence

BACKGROUND

Among early adolescents in the United States (U.S.), the prevalence of cigarette smoking is at its lowest level in recent decades. Nonetheless, given the risks of smoking in early development, it remains critically important to study both risk factors for smoking and risks from smoking. This longitudinal study with U.S. early adolescents examines smoking initiation and tests a model of reciprocal prediction between ever smoking and the personality trait of urgency (i.e., mood-based impulsivity), a trait that increases risk for multiple forms of dysfunction.

METHODS

Participants (n=1906; 90% 10-11 years old, 50% female, 39% racial minorities at baseline) completed questionnaires 1-2 times per year starting in 5th grade and ending in 9th grade. Structural equation modeling allowed tests of bidirectional relationships between ever smoking and urgency controlling for pubertal status and negative affect at each wave.

RESULTS

Incidence of ever smoking increased from 5% to 27% over time, with current smoking around 5% at the last wave. Urgency at each wave predicted ever smoking at the next wave above and beyond covariates and prior smoking (all p<0.01). Likewise, with one exception, ever smoking predicted an increase in urgency at the subsequent wave above and beyond covariates and prior urgency (all p<0.05).

CONCLUSION

Results show that risk for smoking increases with higher levels of urgency and urgency increases secondary to engagement in smoking. Future work should therefore explore urgency as a point of prevention for smoking and smoking cessation as a means to mitigate mood-based impulsivity.

Acute effects of methylphenidate on impulsivity and attentional behavior among adolescents comorbid for ADHD and conduct disorder

Adolescents with Attention Deficit Hyperactivity Disorder (ADHD) and Conduct Disorder (CD) experience deficits in neuropsychological measures of attention, inhibition, and reward processes. Methylphenidate treatment for ADHD and CD has acute effects on these processes. Some of these same aspects of performance are separately described in the Behavioral Model of Impulsivity, which uses a modified approach to measurement. This study characterized the acute effects of methylphenidate attention, initiation, inhibition, and reward processes described in this model of impulsivity. Thirty-one adolescents from the United States of America with comorbid ADHD and CD completed measures of impulsivity (response initiation, response inhibition, and consequence) and attention following placebo, 20 mg, and 40 mg of a long-acting dose of methylphenidate. Methylphenidate effects on attentional performance was more robust than on any of the measures of impulsivity. Adolescent performance from this behavioral perspective is interpreted in the context of divergence from previous neuropsychological tests of acute methylphenidate effects.

Progesterone attenuates impulsive action in a Go/No-Go task for sucrose pellets in female and male rats

Impulsivity, or a tendency to act without anticipation of future consequences, is associated with drug abuse. Impulsivity is typically separated into two main measures, impulsive action and impulsive choice. Given the association of impulsivity and drug abuse, treatments that reduce impulsivity have been proposed as an effective method for countering drug addiction. Progesterone has emerged as a promising treatment, as it is associated with decreased addiction-related behaviors and impulsive action. The goal of the present study was to determine the effects of progesterone (PRO) on impulsive action for food: a Go/No-Go task. Female and male rats responded for sucrose pellets during a Go component when lever pressing was reinforced on a variable-interval 30-s schedule. During the alternate No-Go component, withholding a lever press was reinforced on a differential reinforcement of other (DRO) behavior 30-s schedule, where a lever press reset the DRO timer. Impulsive action was operationally defined as the inability to withhold a response during the No-Go component (i.e. the number of DRO resets). Once Go/No-Go behavior was stable, responding between rats treated with PRO (0.5mg/kg) or vehicle was examined. Progesterone significantly decreased the total number of DRO resets in both males and females, but it did not affect VI responding for sucrose pellets. This suggests that PRO decreases motor impulsivity for sucrose pellets without affecting motivation for food. Thus, PRO may reduce motor impulsivity, a behavior underlying drug addiction.

Effects of yohimbine and drug cues on impulsivity and attention in cocaine-dependent men and women and sex-matched controls

BACKGROUND

Deficits in executive function have been associated with risk for relapse. Data from previous studies suggest that relapse may be triggered by stress and drug-paired cues and that there are significant sex differences in the magnitude of these responses. The aim of this study was to examine the impact of the pharmacological stressor and alpha-2 adrenergic receptor antagonist yohimbine and cocaine cues on executive function in cocaine-dependent men and women.

METHODS

In a double-blind placebo controlled cross-over study, cocaine-dependent men (n=12), cocaine-dependent women (n=27), control men (n=31) and control women (n=25) received either yohimbine or placebo prior to two cocaine cue exposure sessions. Participants performed the Connors' Continuous Performance Test II prior to medication/placebo administration and immediately after each cue exposure session

RESULTS

Healthy controls had a significant increase in commission errors under the yohimbine condition [RR (95% CI)=1.1 (1.0-1.3), χ(2)1=2.0, p=0.050]. Cocaine-dependent individuals exhibited a significant decrease in omission errors under the yohimbine condition [RR (95% CI)=0.6 (0.4-0.8), χ(2)1=8.6, p=0.003]. Cocaine-dependent women had more omission errors as compared to cocaine-dependent men regardless of treatment [RR (95% CI)=7.2 (3.6-14.7), χ(2)1=30.1, p<0.001]. Cocaine-dependent women exhibited a slower hit reaction time as compared to cocaine-dependent men [Female 354 ± 13 vs. Male 415 ± 14; t89=2.6, p=0.012].

CONCLUSIONS

These data add to a growing literature demonstrating significant sex differences in behaviors associated with relapse in cocaine-dependent individuals.

A Computational Analysis of Aberrant Delay Discounting in Psychiatric Disorders

Impatience for reward is a facet of many psychiatric disorders. We draw attention to a growing literature finding greater discounting of delayed reward, an important aspect of impatience, across a range of psychiatric disorders. We propose these findings are best understood by considering the goals and motivation for discounting future reward. We characterize these as arising from either the opportunity costs of waiting or the uncertainty associated with delayed reward. We link specific instances of higher discounting in psychiatric disorder to heightened subjective estimates of either of these factors. We propose these costs are learned and represented based either on a flexible cognitive model of the world, an accumulation of previous experience, or through evolutionary specification. Any of these can be considered suboptimal for the individual if the resulting behavior results in impairments in personal and social functioning and/or in distress. By considering the neurochemical and neuroanatomical implementation of these processes, we illustrate how this approach can in principle unite social, psychological and biological conceptions of impulsive choice.

Longitudinal Associations among Impulsivity, Friend Substance Use, and Adolescent Substance Use

Adolescent substance use is an increasing problem in the United States, and some researchers posit a bidirectional relation between adolescent substance use and the personality trait of impulsivity (e.g., Quinn, Stappenbeck, & Fromme, 2011). Friend substance use has been shown to be a powerful predictor of adolescent substance use, with prior research suggesting a bidirectional relation between adolescent substance use and friend substance use (e.g., Simons-Morton & Chen, 2006). Extant literature has not tested the bidirectional relation between adolescent substance use and impulsivity with longitudinal data nor has it examined this relation while considering the bidirectional relation with the social context factor of friend substance use. Using three waves of longitudinal data, we tested if there was a bidirectional relation between adolescent substance use and impulsivity while also examining the influences of friend substance use. Participants were 131 adolescents (male = 55%, mean age = 13 years at Wave 1). We tested nested models and examined whether adding equality constraints degraded the model fit using a Wald test. Results of structural equation modeling indicated that, after controlling for baseline levels of substance use, impulsivity predicted adolescent and friend substance use over time, whereas adolescent and friend substance use did not predict impulsivity. Adolescents with substance using friends were likely to increase their own substance use. The findings imply that aiming at both improving adolescents’ ability to regulate impulsivity and deterring associations with friends who are using substances is essential for prevention and intervention efforts against substance use development in adolescents.

Sex differences in self-report and behavioral measures of disinhibition predicting marijuana use across adolescence

Disinhibition has been consistently linked to substance use across development. Recent research suggests, however, that these relations may be influenced by both sex and measurement approach. The current study examined the moderating effect of sex on the association between behavioral and self-report measures of disinhibition and marijuana use across adolescence. Participants were 115 boys and 89 girls initially evaluated at Grade 8 using a laboratory behavioral assessment and self-report questionnaires of disinhibitory variables. Marijuana use was measured annually from Grades 9 through 12. Results suggest that boys and girls did not differ on either self-reported or behaviorally assessed levels of disinhibition, and that disinhibition measured using both approaches was associated with increases in marijuana use over time. There was a significant interaction between sex and disinhibition, suggesting that boys (but not girls) who self-reported elevations in disinhibition evidenced greater increases in marijuana use. The current findings add to a growing literature supporting the importance of using multiple methods to assess disinhibition and highlight the critical role of biological sex in understanding these relations.

Striatal D1- and D2-type dopamine receptors are linked to motor response inhibition in human subjects

Motor response inhibition is mediated by neural circuits involving dopaminergic transmission; however, the relative contributions of dopaminergic signaling via D1- and D2-type receptors are unclear. Although evidence supports dissociable contributions of D1- and D2-type receptors to response inhibition in rats and associations of D2-type receptors to response inhibition in humans, the relationship between D1-type receptors and response inhibition has not been evaluated in humans. Here, we tested whether individual differences in striatal D1- and D2-type receptors are related to response inhibition in human subjects, possibly in opposing ways. Thirty-one volunteers participated. Response inhibition was indexed by stop-signal reaction time on the stop-signal task and commission errors on the continuous performance task, and tested for association with striatal D1- and D2-type receptor availability [binding potential referred to nondisplaceable uptake (BPND)], measured using positron emission tomography with [(11)C]NNC-112 and [(18)F]fallypride, respectively. Stop-signal reaction time was negatively correlated with D1- and D2-type BPND in whole striatum, with significant relationships involving the dorsal striatum, but not the ventral striatum, and no significant correlations involving the continuous performance task. The results indicate that dopamine D1- and D2-type receptors are associated with response inhibition, and identify the dorsal striatum as an important locus of dopaminergic control in stopping. Moreover, the similar contribution of both receptor subtypes suggests the importance of a relative balance between phasic and tonic dopaminergic activity subserved by D1- and D2-type receptors, respectively, in support of response inhibition. The results also suggest that the stop-signal task and the continuous performance task use different neurochemical mechanisms subserving motor response inhibition.

Increased impulsivity in pathological gambling: Considering nicotine dependence

INTRODUCTION

It has been highlighted that increased impulsivity is an important etiological factor in pathological gambling (PG). However, the role of the highly prevalent comorbid mental disorders in PG remains unclear. This is of special concern as the highest comorbidity was found between PG and nicotine dependence (ND), which, in turn, has also been associated with heightened impulsivity. This study aimed to find out whether increased impulsivity in PG is a specific characteristic related to comorbid mental disorders in general or especially to ND.

METHOD

A cross-sectional study was designed that included a healthy control group and three disorder groups with comorbid PG excluding ND, comorbid PG including ND, and ND alone according to the Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition. Impulsivity was assessed according to the dimensions response and choice impulsivity applying behavioral and self-report measures.

RESULTS

We found (a) increased response impulsivity in the comorbid PG group when compared to the control group. Furthermore, increased choice impulsivity was found (b) in comorbid PG excluding ND and (c) in comorbid PG including ND when compared to ND alone. Other group differences did not reach significance.

CONCLUSIONS

Our findings highlight that comorbid PG shares deficits in inhibitory control with ND. In contrast, maladaptive choices are a specific disorder characteristic of comorbid PG when compared to ND. If replicated in further studies, intervention strategies strengthening cognitive control skills might be effective for comorbid PG as well as ND whereas strategies enhancing maladaptive valuation of rewards might be specifically effective in comorbid PG.

Cigarette Cravings, Impulsivity, and the Brain

Craving is a core feature of tobacco use disorder as well as a significant predictor of smoking relapse. Studies have shown that appetitive smoking-related stimuli (e.g., someone smoking) trigger significant cravings in smokers impede their self-control capacities and promote drug seeking behavior. In this review, we begin by an overview of functional magnetic resonance imaging (fMRI) studies investigating the neural correlates of smokers to appetitive smoking cues. The literature reveals a complex and vastly distributed neuronal network underlying smokers' craving response that recruits regions involved in self-referential processing, planning/regulatory processes, emotional responding, attentional biases, and automatic conducts. We then selectively review important factors contributing to the heterogeneity of results that significantly limit the implications of these findings, namely between- (abstinence, smoking expectancies, and self-regulation) and within-studies factors (severity of smoking dependence, sex-differences, motivation to quit, and genetic factors). Remarkably, we found that little to no attention has been devoted to examine the influence of personality traits on the neural correlates of cigarette cravings in fMRI studies. Impulsivity has been linked with craving and relapse in substance and tobacco use, which prompted our research team to examine the influence of impulsivity on cigarette cravings in an fMRI study. We found that the influence of impulsivity on cigarette cravings was mediated by fronto-cingulate mechanisms. Given the high prevalence of cigarette smoking in several psychiatric disorders that are characterized by significant levels of impulsivity, we conclude by identifying psychiatric patients as a target population whose tobacco-smoking habits deserve further behavioral and neuro-imaging investigation.

Sex differences in impulsive action and impulsive choice

Here, we review the evidence for sex differences in behavioral measures of impulsivity for both humans and laboratory animals. We focus on two specific components of impulsivity: impulsive action (i.e., difficulty inhibiting a prepotent response) and impulsive choice (i.e., difficulty delaying gratification). Sex differences appear to exist on these measures, but the direction and magnitude of the differences vary. In laboratory animals, impulsive action is typically greater in males than females, whereas impulsive choice is typically greater in females. In humans, women discount more steeply than men, but sex differences on measures of impulsive action depend on tasks and subject samples. We discuss implications of these findings as they relate to drug addiction. We also point out the major gaps in this research to date, including the lack of studies designed specifically to examine sex differences in behavioral impulsivity, and the lack of consideration of menstrual or estrous phase or sex hormone levels in the studies.

Role of CNR1 polymorphisms in moderating the effects of psychosocial adversity on impulsivity in adolescents

Enhanced endocannabinoid signaling has been implicated in typically adolescent behavioral features such as increased risk-taking, impulsivity and novelty seeking. Research investigating the impact of genetic variants in the cannabinoid receptor 1 gene (CNR1) and of early rearing conditions has demonstrated that both factors contribute to the prediction of impulsivity-related phenotypes. The present study aimed to test the hypothesis of an interaction of the two most studied CNR1 polymorphisms rs806379 and rs1049353 with early psychosocial adversity in terms of affecting impulsivity in 15-year-olds from an epidemiological cohort sample followed since birth. In 323 adolescents (170 girls, 153 boys), problems of impulse control and novelty seeking were assessed using parent-report and self-report, respectively. Exposure to early psychosocial adversity was determined in a parent interview conducted at the age of 3 months. The results indicated that impulsivity increased following exposure to early psychosocial adversity, with this increase being dependent on CNR1 genotype. In contrast, while individuals exposed to early adversity scored higher on novelty seeking, no significant impact of genotype or the interaction thereof was detected. This is the first evidence to suggest that the interaction of CNR1 gene variants with the experience of early life adversity may play a role in determining adolescent impulsive behavior. However, given that the reported findings are obtained in a high-risk community sample, results are restricted in terms of interpretation and generalization. Future research is needed to replicate these findings and to identify the mediating mechanisms underlying this effect.

Dysfunctional decision-making in pathological gambling: pattern specificity and the role of impulsivity

Dysfunctional decision-making in individuals with pathological gambling (PGs) may result from dominating reward-driven processes, indicated by higher impulsivity. In the current study we examined (1) if PGs show specific decision-making impairments related to dominating reward-driven processes rather than to strategic planning deficits and (2) whether these impairments are related to impulsivity. Nineteen PGs according to DSM-IV and 19 matched control subjects undertook the Cambridge Gambling Task (CGT) to assess decision-making. The delay discounting paradigm (DDP) as well as the UPPS Impulsive Behavior Scale (measuring urgency, premeditation, perseverance and sensation seeking) were administered as multidimensional measures of impulsivity. Results revealed that (1) PGs exhibited higher risk seeking and an immediate reward focus in the CGT and, in contrast, comparable strategic planning to the control group. (2) Decision-making impairments were related to more severe delay discounting and, specifically, to increased urgency and less premeditation. Our findings suggest (1) the necessity to disentangle decision-making components in order to improve etiological models of PGs, and (2) that urgency and premeditation are specifically related to disadvantageous decision-making and should be tackled in intervention strategies focusing on emotion tolerance and control strategies.

Relative effects of social self-control, sensation seeking, and impulsivity on future cigarette use in a sample of high-risk adolescents

We used confirmatory factor analysis to compare convergence/divergence across self-report measures of social self-control, sensation seeking, and impulsivity in a sample of high-risk adolescents. In addition, we tested baseline social self-control as a predictor of cigarette use one year later, controlling for baseline cigarette use, impulsivity/sensation seeking, and demographic variables. Data were collected in 2004-2005 from 821 adolescents (M age = 16.3; SD = 1.36) enrolled in 14 continuation high schools in Southern California. Of the baseline sample, 566 students participated in a follow-up survey one year later. Results indicated that social self-control represents a unique dimension of self-control and is a salient predictor of future cigarette use.

Effects of transcranial direct current stimulation on risky decision making are mediated by 'hot' and 'cold' decisions, personality, and hemisphere

Previous results point towards a lateralization of dorsolateral prefrontal cortex (DLPFC) function in risky decision making. While the right hemisphere seems involved in inhibitory cognitive control of affective impulses, the left DLPFC is crucial in the deliberative processing of information relevant for the decision. However, a lack of empirical evidence precludes definitive conclusions. The aim of our study was to determine whether anodal transcranial direct current stimulation (tDCS) over the right DLPFC with cathodal tDCS over the lDLPFC (anodal right/cathodal left) or vice versa (anodal left/cathodal right) differentially modulates risk-taking in a task [the Columbia Card Task (CCT)] specifically engaging affect-charged (Hot CCT) vs. deliberative (Cold CCT) decision making. The facilitating effect of the anodal stimulation on neuronal activity was emphasized by the use of a small anode and a big cathode. To investigate the role of individual differences in risk-taking, participants were either smokers or non-smokers. Anodal left/cathodal right stimulation decreased risk-taking in the 'cold' cognition version of the task, in both groups, probably by modulating deliberative processing. In the 'hot' version, anodal right/cathodal left stimulation led to opposite effects in smokers and non-smokers, which might be explained by the engagement of the same inhibitory control mechanism: in smokers, improved controllability of risk-seeking impulsivity led to more conservative decisions, while inhibition of risk-aversion in non-smokers resulted in riskier choices. These results provide evidence for a hemispheric asymmetry and personality-dependent tDCS effects in risky decision making, and may be important for clinical research on addiction and depression.

Greater risk sensitivity of dorsolateral prefrontal cortex in young smokers than in nonsmokers

RATIONALE

Despite a national reduction in the prevalence of cigarette smoking, ~19% of the adult US population persists in this behavior, with the highest prevalence among 18-25-year-olds. Given that the choice to smoke imposes a known health risk, clarification of brain function related to decision-making, particularly involving risk-taking, in smokers may inform prevention and smoking cessation strategies.

OBJECTIVES

This study aimed to compare brain function related to decision-making in young smokers and nonsmokers.

METHODS

The Balloon Analogue Risk Task (BART) is a computerized risky decision-making task in which participants pump virtual balloons, each pump associated with an incremental increase in potential payoff on a given trial but also with greater risk of balloon explosion and loss of payoff. We used this task to compare brain activation associated with risky decision-making in smokers (n = 18) and nonsmokers (n = 25), while they performed the BART during functional magnetic resonance imaging (fMRI). The participants were young men and women, 17-21 years of age.

RESULTS

Risk level (number of pumps) modulated brain activation in the right dorsolateral and ventrolateral prefrontal cortices more in smokers than in nonsmokers, and smoking severity (Heaviness of Smoking Index) was positively related to this modulation in an adjacent frontal region.

CONCLUSIONS

Given evidence for involvement of the right dorsolateral and ventrolateral prefrontal cortices in inhibitory control, these findings suggest that young smokers have a different contribution of prefrontal cortical substrates to risky decision-making than nonsmokers. Future studies are warranted to determine whether the observed neurobiological differences precede or result from smoking.

The behavioral- and neuro-economic process of temporal discounting: A candidate behavioral marker of addiction

Addiction science would benefit from the identification of a behavioral marker. A behavioral marker could reflect the projected clinical course of the disorder, function as a surrogate measure of clinical outcome, and/or may be related to biological components that underlie the disorder. In this paper we review relevant literature, made possible with the early and sustained support by NIDA, to determine whether temporal discounting, a neurobehavioral process derived from behavioral economics and further explored through neuroeconomics, may function as a behavioral marker. Our review suggests that temporal discounting 1) identifies individuals who are drug-dependent, 2) identifies those at risk of developing drug dependence, 3) acts as a gauge of addiction severity, 4) correlates with all stages of addiction development, 5) changes with effective treatment, and 6) may be related to the biological and genetic processes that underlie addiction. Thus, initial evidence supports temporal discounting as a candidate behavioral marker. Additional studies will be required in several areas for a more conclusive determination. Confirmation that temporal discounting functions as a behavioral marker for addiction could lead to 1) a screen for new treatments, 2) personalization of prevention and treatment interventions, and 3) the extension of temporal discounting as a behavioral marker for other etiologically similar disorders. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.

Test-retest reliability and construct validity of the Experiential Discounting Task

Delay discounting (the devaluation of delayed rewards) has been studied extensively using animal models with psychophysical adjustment procedures. Similar procedures have been developed to assess delay discounting in humans and these procedures most often use hypothetical rewards and delays. The Experiential Discounting Task (EDT) was developed to assess human delay discounting using real rewards and delays. In the present study we examined the test-retest reliability and construct validity of the EDT. Construct validity was evaluated by comparing it with a standard delay discounting task. The EDT had poor test-retest reliability and discounting rates obtained with this task were uncorrelated with those obtained in the standard delay discounting task. Area under the EDT discounting curve was negatively correlated with scores on a measure of boredom proneness (i.e., individuals prone to boredom more steeply discounted delayed money in the EDT). This correlation may underlie previous reports that discounting in the EDT is correlated with addictions, as some evidence suggests boredom proneness is correlated with gambling, cigarette smoking, alcohol consumption, and sensation seeking. Boredom proneness scores were correlated with no other measure of discounting. These findings suggest the EDT measures a different construct than that measured by traditional delay discounting tasks.

The relationship between impulsivity, risk-taking propensity and nicotine dependence among older adolescent smokers

Impulsivity and risk-taking propensity are neurobehavioral traits that reliably distinguish between smoking and non-smoking adults. However, how these traits relate to smoking quantity and nicotine dependence among older adolescent smokers is unclear. The current study examined impulsivity and risk-taking propensity in relation to smoking behavior and nicotine dependence among current older adolescent smokers (age 16-20 years; N=107). Participants completed the Barratt Impulsiveness Scale-11 (BIS-11), the Balloon Analogue Risk Task (BART), and self-report measures of smoking behavior and nicotine dependence. Results indicated a significant positive relationship between nicotine dependence and the Attention subscale (β=.20, t=2.07, p<.05) and the Non-planning subscale (β=.19, t=1.92, p<.06) of the BIS-11. Contrary to expectation, the results also indicated a significant negative relationship between performance on the BART and nicotine dependence (β=-.19, t=-2.18, p<.05), such that greater risk-taking propensity was associated with less dependence. These data suggest that impulsivity and risk-taking propensity are related to older adolescent smoking but are separable traits with distinguishable associations with nicotine dependence among adolescents. These findings support the notion that impulsivity is related to heightened nicotine dependence, but suggest that the relationship between risk-taking propensity and nicotine dependence is more ambiguous and warrants further investigation.

The 5-HT2C receptor agonist lorcaserin reduces nicotine self-administration, discrimination, and reinstatement: relationship to feeding behavior and impulse control

Lorcaserin ((1R)-8-chloro-1-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine HCl) is a selective 5-HT(2C) receptor agonist with clinical efficacy in phase-III obesity trials. Based on evidence that this drug class also affects behaviors motivated by drug reinforcement, we compared the effect of lorcaserin on behavior maintained by food and nicotine reinforcement, as well as the stimulant and discriminative stimulus properties of nicotine in the rat. Acutely administered lorcaserin (0.3-3 mg/kg, subcutaneous (SC)) dose dependently reduced feeding induced by 22-h food deprivation or palatability. Effects up to 1 mg/kg were consistent with a specific effect on feeding motivation. Lorcaserin (0.6-1 mg/kg, SC) reduced operant responding for food on progressive and fixed ratio schedules of reinforcement. In this dose range lorcaserin also reversed the motor stimulant effect of nicotine, reduced intravenous self-administration of nicotine, and attenuated the nicotine cue in rats trained to discriminate nicotine from saline. Lorcaserin also reduced the reinstatement of nicotine-seeking behavior elicited by a compound cue comprising a nicotine prime and conditioned stimulus previously paired with nicotine reinforcement. Lorcaserin did not reinstate nicotine-seeking behavior or substitute for a nicotine cue. Finally, lorcaserin (0.3-1 mg/kg) reduced nicotine-induced increases in anticipatory responding, a measure of impulsive action, in rats performing the five-choice serial reaction time task. Importantly, these results indicate that lorcaserin, and likely other selective 5-HT(2C) receptor agonists, similarly affect both food- and nicotine-motivated behaviors, and nicotine-induced impulsivity. Collectively, these findings highlight a therapeutic potential for 5-HT(2C) agonists such as lorcaserin beyond obesity into addictive behaviors, such as nicotine dependence.

Delay discounting by adolescents experimenting with cigarette smoking

AIMS

To evaluate delay discounting and self-reported impulsive behavior in a sample of adolescents experimenting with cigarette smoking compared with adolescents who had never smoked or were daily smokers.

DESIGN

A cross-sectional design was used to compare smoking-status groups.

SETTING

Columbus, Ohio, a city of approximately 780,000 people.

PARTICIPANTS

A sample of 141 male and female adolescents with a mean age of 15.37 (standard deviation = 1.09) years.

MEASUREMENTS

Primary measures included a computerized assessment of delay discounting, a self-report assessment of impulsivity [Barratt Impulsiveness Scale-adolescent (BIS-11-A)] and verifications of cigarette smoking status (breath carbon monoxide and urinary cotinine level).

FINDINGS

Smokers discounted more by delay and had higher impulsivity scores than non-smokers. Experimenters had scores intermediate to those of smokers and non-smokers on both measures. In some analyses the difference between experimenters and non-smokers was significant, with experimenters showing greater delay discounting, but in no case did experimenters differ significantly from the smokers.

CONCLUSIONS

Young people who experiment with cigarettes appear to be similar to those who smoke regularly in terms of tendency to discount future gains and report impulsive tendencies, and generally higher in these traits than non-smokers.

Acute nicotine increases both impulsive choice and behavioural disinhibition in rats

RATIONALE

Heavy smokers exhibit greater levels of impulsive choice and behavioural disinhibition than non-smokers. To date, however, the relationship between nicotine use and differing dimensions of impulsivity has not been systematically assessed.

OBJECTIVES

A series of studies was designed to assess the acute dose-response effects of nicotine and the nicotinic receptor antagonist mecamylamine alone, and in combination with nicotine, on impulsive choice and behavioural disinhibition in rats.

METHODS

Separate groups of rats were trained on a symmetrically reinforced go/no-go task to measure levels of disinhibition and a systematic delayed reward task to measure levels of impulsive choice. Once trained, all animals in each task were treated acutely with nicotine (0.125, 0.25, 0.5 and 1.0 mg/kg), mecamylamine (0.1, 0.3 and 1.0 mg/kg) and varying doses of mecamylamine (0.1, 0.3 and 1.0 mg/kg) prior to nicotine (0.5 mg/kg). An additional experiment assessed the effects of alterations in primary motivation (presatiation and fasting) on performance in both tasks.

RESULTS

Acute nicotine increased both impulsive choice and behavioural disinhibition, effects that were blocked by pre-treatment with mecamylamine. Mecamylamine when administered alone did not alter impulsive behaviour. The lack of effect of presatiation on performance measures suggests that the observed nicotine-induced impulsivity cannot be attributed to the anorectic activity of the compound.

CONCLUSIONS

Present findings support the hypothesis that heightened impulsivity in smokers may in part be a consequence of the direct acute effects of nicotine. As such, drug-induced changes in impulsivity may play a critical role in the transition to and maintenance of nicotine dependence.

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.