Neurocognitive and neuroimaging evidence of behavioural dysregulation in human drug addiction: implications for diagnosis, treatment and prevention

Understanding sex differences and the translational value of models of persistent substance use despite negative consequences

Persistent substance use despite negative consequences is a key facet of substance use disorder. The last decade has seen the preclinical field adopt the use of punishment to model adverse consequences associated with substance use. This has largely involved the pairing of drug use with either electric foot shock or quinine, a bitter tastant. Whilst at face value, these punishers may model aspects of the physical and psychological consequences of substance use, such models are yet to assist the development of approved medications for treatment. This review discusses progress made with animal models of punishment to understand the behavioral consequences of persistent substance use despite negative consequences. We highlight the importance of examining sex differences, especially when the behavioral response to punishment changes following drug exposure. Finally, we critique the translational value these models provide for the substance use disorder field.

Attention-deficit/hyperactivity disorder combined subtype exacerbates opioid use disorder consequences: Mediation by impulsive phenotypes

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is highly prevalent and associated with opioid use disorder (OUD). Yet, little is known about the mechanisms by which ADHD (which is a heterogeneous construct/diagnosis) might alter the trajectory of OUD outcomes in persons who use heroin.

AIM

We examined whether ADHD subtypes are related to heroin-use consequences and the extent to which the effects of ADHD on lifetime heroin-use consequences are mediated by two impulsivity factors that may be partly independent of ADHD: foreshortened time perspective and drug-use impulsivity.

METHODS

Individuals who reported regular heroin use (N=250) were screened using the Assessment of Hyperactivity and Attention (AHA), Impulsive Relapse Questionnaire (IRQ), Stanford Time Perception Inventory (STPI), and a comprehensive assessment of lifetime and current substance use and substance-related consequences. This secondary analysis examined whether ADHD or intermediate phenotypes predicted heroin-use consequences.

RESULTS

Relative to participants whose AHA scores indicated lifetime absence of ADHD (n=88), those with scores indicating persistent ADHD (childhood and adult, n=62) endorsed significantly more total lifetime heroin-use consequences despite comparable heroin-use severity. Likewise, there was a significant indirect effect of the combined ADHD subtype in childhood on lifetime heroin-use consequences. This effect was mediated by STPI scores indicating less future (and more hedonism in the present) temporal orientation and by IRQ scores indicating less capacity for delaying drug use.

CONCLUSION

The combined ADHD subtype is significantly associated with lifetime heroin-use consequences, and this effect is mediated through higher drug-use impulsivity (less capacity for delay) and lower future temporal orientation.

Neurocognitive predictors of addiction-related outcomes: A systematic review of longitudinal studies

It is well-established that addiction is typically associated with a distinct pattern of neurocognitive functioning with a consensus that it is typified by impaired top-down executive control and aberrant risk-reward processing. Despite a consensus that neurocognition plays an important role in characterizing and maintaining addictive disorders, there is a lack of systematic, bottom-up synthesis of quantitative evidence showing that neurocognition predicts addictive behaviors, and which neurocognitive constructs have the best predictive validity. This systematic review aimed to assess whether cognitive control and risk-reward processes as defined by the Research Domain Criteria (RDoC) predict the development and maintenance of addictive behaviors specifically, consumption, severity, and relapse. The findings from this review expose the substantial lack of evidence for neurocognition predicting addiction outcomes. However, there is evidence that suggests reward-related neurocognitive processes may be important for the detection of early risk for addiction, as well as a potentially viable target for designing novel, more effective interventions.

Alcohol-induced brain deficit in alcohol dependence

Although numerous adverse effects of alcohol addiction on health, behavior, and brain function were widely reported, the neurobiological mechanism of alcohol dependence remains largely unknown. In this study, a total of twenty-nine patients with alcohol dependence and twenty-nine status-matched normal controls (NCs) were recruited. Percent amplitude of fluctuation (PerAF) was applied to identify alcohol-related brain activity deficits. We found that alcohol dependence was associated with widespread differences in the left orbitofrontal cortex, right higher visual cortex, right supramarginal gyrus, right postcentral gyrus, and bilateral cerebellum posterior lobe with decreased PerAF, but no brain areas with increased PerAF differences were found. ROC curve showed that decreased PerAF revealed extremely high discriminatory power with a high AUC value of 0.953, as well as a high degree of sensitivity (96.6%) and specificity (86.2%), in distinguishing patients with alcohol dependence from NCs. In the alcohol dependence group, the amount of daily alcohol consumption showed significant negative correlations with the right cerebellum posterior lobe and right higher visual cortex. These findings suggest that the cerebellar-visual-orbitofrontal circuit was disturbed by alcohol dependence. The proposed new method of PerAF may be served as a potential biomarker to identify the regional brain activity deficits of alcohol dependence.

Substance-Use Disorders in Children and Adolescents

BACKGROUND

The most common substance use disorders in childhood and adolescence have to do with alcohol and cannabis. These disorders begin as early as puberty, are often accompanied by other mental disorders, and, if untreated, very frequently persist into adulthood.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed on substance use disorders in children and adolescents.

RESULTS

Substance use disorders are among the commonest mental disorders in childhood and adolescence. In Germany, approximately 10% of adolescents have tried cannabis at least once. The prognosis is negatively affected by individual (bio-)psychological traits, mental comorbidities, laws that facilitate consumption, socioeconomic disadvantage, consuming peers, and parental substance use disorders. A timely diagnosis, motivation by the pediatrician, and referral to specialized child and adolescent psychiatric services helps assure that those affected receive appropriate treatment, with the goal of abstinence from the substance as well as improvement in emotional regulation, affectivity, and attention. According to studies from the English-speaking countries and considering all treatment forms, treatment is completed by approximately 60% to 65% of children and adolescents; 20% to 40% of these patients are abstinent six months after the end of treatment. No studies of this type have been carried out to date in Germany.

CONCLUSION

As the results of treatment are generally poor, there is a major need for research on the treatment and care of children and adolescents with substance use disorders. In particular, the interfaces between outpatient and inpatient care need further improvement.

Resting State EEG Activity Related to Impulsivity in People with Prescription Opioid Use Disorder

Previous studies on EEG activity in prescription opioid use disorder (OUD) have reported neuronal dysfunction related to heroin use, most consistently reflected by increases in β-brain oscillations. As similar research has yet to examine EEG associated with non-medical use of prescription opioid and as inhibitory deficits are associated with OUD, this pilot study compared quantitative EEGs of 18 patients with prescription OUD and 18 healthy volunteers and assessed relationships between oscillatory activity and impulsivity with the Barratt Impulsiveness Scale (BIS-11). Spectral EEGs showed greater amplitude density in β₁, β₂, and β₃ frequencies across frontal, temporal-central and posterior recording areas in patients. Similar abnormal amplitude density increases were seen in δ but not in θ or α frequency bands. Patients exhibited greater scores (impaired impulse control) on BIS-11 subscales (attention, motor, self-control) and impairment of these impulsive subtypes was associated with increases in β and δ oscillations. In patients, β1, β2, and δ activity was positively associated with disorder severity. Taken together, the results suggest that altered brain oscillations in persons with prescription OUD show some similarities with reported oscillatory changes in heroin use and may indicate a chronic state of imbalance in neuronal networks regulating impulsive and inhibitory control systems.

Cingulate circuits are associated with escalation of heroin use and naloxone-induced increases in heroin self-administration

Opioid use disorder (OUD) is defined as a compulsion to seek and take opioids, loss of control over intake and the development of a negative emotional state when access to opioids is denied. Using functional magnetic resonance imaging (fMRI) data in a rat model of OUD, we demonstrate that the escalation of heroin self-administration (SA) and the increased heroin SA following an injection of an opioid receptor antagonist (naloxone) are associated with changes in distinct brain circuits, centered on the cingulate cortex (Cg). Here, SA escalation score was negatively associated with changes in resting state functional connectivity (rsFC) between the Cg and the dorsal striatum. Conversely, increased heroin SA following naloxone injection, was associated with increased connectivity between the Cg and the extended amygdala and hypothalamus. Naloxone-induced increased SA was also positively associated with changes in the amplitude of low frequency fluctuations within the Cg, a measure of spontaneous neuronal activity. Characterizing the distinct brain circuit and behavior changes associated with different facets of addiction increases our understanding of OUD and may provide insight into addiction prevention and treatment.

The Effects of Combined Physical and Cognitive Training on Inhibitory Control: A Systematic Review and Meta-Analysis

While strong inhibitory control is critical for health and wellbeing, there are no broadly applicable effective behavioural interventions that enhance it. This meta-analysis examined the neurocognitive rationale for combined physical and cognitive training and synthesised the rapidly growing body of evidence examining combined paradigms to enhance inhibitory control. Across the research to date, there was a small positive effect (n studies = 16, n participants = 832) of combined training on improving inhibitory control. Sub-group analyses showed small-moderate positive effects when the physical component of the combined training was moderately intense, as opposed to low or vigorous intensities; moderate positive effects were found in older adults, as compared to adolescents and adults; and healthy individuals and those with vascular cognitive impairment, as compared to ADHD, ASD, mild cognitive impairment and cancer survivors. This is the first meta-analysis to provide evidence that combined physical, specifically when moderately intense, and cognitive training has the capacity to improve inhibitory control, particularly when delivered to healthy individuals and those experiencing age-related decline.

Transition to substance use disorders: impulsivity for reward and learning from reward

Substance dependence constitutes a profound societal burden. Although large numbers of individuals use licit or illicit substances, few transition to dependence. The specific factors influencing this transition are not well understood. Substance-dependent individuals tend to be swayed by the immediate rewards of drug taking, but are often insensitive to delayed negative consequences of their behavior. Dependence is consequently associated with impulsivity for reward and atypical learning from feedback. Behavioral impulsivity is indexed using tasks measuring spontaneous decision-making and capacity to control impulses. While evidence indicates drug taking exacerbates behavioral impulsivity for reward, animal and human studies of drug naïve populations demonstrate it might precede any drug-related problems. Research suggests dependent individuals are also more likely to learn from rewarding (relative to punishing) feedback. This may partly explain why substance-dependent individuals fail to modify their behavior in response to negative outcomes. This enhanced learning from reward may constitute a further pre-existing risk factor for substance dependence. Although impulsivity for reward and preferential learning from rewarding feedback are both underpinned by a compromised dopaminergic system, few studies have examined the relationship between these two mechanisms. The interplay of these processes may help enrich understanding of why some individuals transition to substance dependence.

Voluntary decision-making in addiction: A comprehensive review of existing measurement tools

The notion of voluntariness, notably the inability to refrain from using an addictive substance, is central to addiction. This review examines different constructs measuring voluntariness in the context of drug addiction. We found 117 articles featuring 123 distinct scales for 11 of the 16 constructs initially searched. Self-efficacy was by far the construct with most scales. Most scales were not specifically developed with samples of people with addictions. From a methodological standpoint, current literature jeopardizes the validity of generalizations about how voluntariness functions and is measured in people with and without a drug addiction. From the standpoint of social psychology, the study of voluntariness remains anchored in an individualistic orientation to the study of cognition and behavior, thus calling for greater crosstalk between psychology subspecialties.

Factors mediating pain-related risk for opioid use disorder

Pain is a complex experience with far-reaching organismal influences ranging from biological factors to those that are psychological and social. Such influences can serve as pain-related risk factors that represent susceptibilities to opioid use disorder. This review evaluates various pain-related risk factors to form a consensus on those that facilitate opioid abuse. Epidemiological findings represent a high degree of co-occurrence between chronic pain and opioid use disorder that is, in part, driven by an increase in the availability of opioid analgesics and the diversion of their use in a non-medical context. Brain imaging studies in individuals with chronic pain that use/abuse opioids suggest abuse-related mechanisms that are rooted within mesocorticolimbic processing. Preclinical studies suggest that pain states have a limited impact on increasing the rewarding effects of opioids. Indeed, many findings indicate a reduction in the rewarding and reinforcing effects of opioids during pain states. An increase in opioid use may be facilitated by an increase in the availability of opioids and a decrease in access to non-opioid reinforcers that require mobility or social interaction. Moreover, chronic pain and substance abuse conditions are known to impair cognitive function, resulting in deficits in attention and decision making that may promote opioid abuse. A better understanding of pain-related risk factors can improve our knowledge in the development of OUD in persons with pain conditions and can help identify appropriate treatment strategies. This article is part of the special issue on 'Vulnerabilities to Substance Abuse.'.

Impairments in Executive Functioning in Patients with Comorbid Substance Use and Personality Disorders: A Systematic Review

The purpose of this systematic review was to examine the evidence for impaired executive functioning in patients diagnosed with a dual pathology of personality disorder (PD) and substance use disorder, and to identify whether differences exist in comparison to those with a single diagnosis. Methods: A systematic search was conducted to identify studies using measures of executive functioning in patients with PD-substance use disorder dual pathology. Sixteen studies were selected. Results: The results indicate that dual pathology patients with Cluster C personality disorder do not differ from controls, and that the presence of dual pathology does not influence the updating domain of executive functioning. The findings were inconclusive with regard to dual pathology patients with Cluster B personality disorders. Whilst the various studies consistently show that these patients show worse performance than the control groups, here are contradictory results with regard to whether Cluster B personality disorders add more alterations in executive functioning to those that already appear in substance use disorder. Conclusions: The results suggest the need for further research that more adequately controls variables such as time in treatment, medication, and sample size, whilst there is also a need to employ longitudinal designs that include more patients from Clusters A and C.

The Role of Social Reward and Corticostriatal Connectivity in Substance Use

This report describes an ongoing R03 grant that explores the links between trait reward sensitivity, substance use, and neural responses to social and nonsocial reward. Although previous research has shown that trait reward sensitivity and neural responses to reward are linked to substance use, whether this relationship is impacted by how people process social stimuli remains unclear. We are investigating these questions via a neuroimaging study with college-aged participants, using individual difference measures that examine the relation between substance use, social context, and trait reward sensitivity with tasks that measure reward anticipation, strategic behavior, social reward consumption, and the influence of social context on reward processing. We predict that substance use will be tied to distinct patterns of striatal dysfunction. Specifically, reward hyposensitive individuals will exhibit blunted striatal responses to social and non-social reward and enhanced connectivity with the orbitofrontal cortex; in contrast, reward hypersensitive individuals will exhibit enhanced striatal responses to social and non-social reward and blunted connectivity with the orbitofrontal cortex. We also will examine the relation between self-reported reward sensitivity, substance use, and striatal responses to social reward and social context. We predict that individuals reporting the highest levels of substance use will show exaggerated striatal responses to social reward and social context, independent of self-reported reward sensitivity. Examining corticostriatal responses to reward processing will help characterize the relation between reward sensitivity, social context and substance use while providing a foundation for understanding risk factors and isolating neurocognitive mechanisms that may be targeted to increase the efficacy of interventions.

Cannabis and Illicit Drug Use During Neurodevelopment and the Associated Structural, Functional and Cognitive Outcomes: Protocol for a Systematic Review

Background

High rates of cannabis and illicit drug use are experienced by young people during the final stages of neurodevelopment (aged 15-24 years), a period characterized by high neuroplasticity. Frequent drug use during this time may interfere with neurophysiological and neuropsychological development pathways, potentially leading to ongoing unfavorable neuroadaptations. The dose-response relationship between illicit drug use, exposure, and individual neurodevelopmental variation is unknown but salient with global shifts in the legal landscape and increasingly liberal attitudes and perceptions of the harm caused by cannabis and illicit drugs.

Objective

This systematic review aims to synthesize longitudinal studies that investigate the effects of illicit drug use on structural, functional, and cognitive brain domains in individuals under the neural age of adulthood (25 years). This protocol outlines prospective methods that will facilitate an exhaustive review of the literature exploring pre- and post-drug use brain abnormalities arising during neurodevelopment.

Methods

Five electronic databases (Medline, Embase, PsycINFO, ProQuest Central, and Web of Science) will be systematically searched between 1990 and 2019. The search terms will be a combination of MeSH (Medical Subject Headings), with keywords adapted to each database. Study reporting will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and if relevant, study quality will be assessed using the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach. Eligible studies are those that sampled youth exposed to cannabis or illicit drugs and employed neurophysiological or neuropsychological assessment techniques. Studies will be excluded if participants had been clinically diagnosed with any psychiatric, neurological, or pharmacological condition.

Results

This is an ongoing review. As of February 2020, papers are in full-text screening, with results predicted to be complete by July 2020.

Conclusions

Integrating data collected on the three brain domains will enable an assessment of the links between structural, functional, and cognitive brain health across individuals and may support the early detection and prevention of neurodevelopmental harm.

Trial Registration

PROSPERO CRD42020151442; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=151442

International Registered Report Identifier (IRRID)

PRR1-10.2196/18349

Risky decision-making in individuals with substance use disorder: A meta-analysis and meta-regression review

BACKGROUND

This review aims to identify whether risky decision-making is increased in substance users, and the impact of substance type, polysubstance use status, abstinence period, and treatment status on risky decision-making.

METHODS

A literature search with no date restrictions was conducted to identify case-control studies or cross-sectional studies that used behavioral tasks to measure risky decision-making in substance users. A random-effects model was performed. GRADE criteria was used to assess the quality of evidence.

RESULTS

52 studies were enrolled. The result showed that the difference in risky decision-making performance between user groups and control groups was significant (SMD = - 0.590; 95%CI = - 0.849 to - 0.330; p < 0.001; I² = 93.4%; P_{heterogeneity} < 0.001). Subgroup analysis showed that users in the subgroups of alcohol (p < 0.001), tobacco (p < 0.01), cocaine (p < 0.001), opioid (p < 0.001), mixed group (p < 0.01), adult users (p < 0.001), small sample size (p < 0.001), large sample size (p < 0.01), low education (p < 0.001), high education (p < 0.001), short-abstinence period (p < 0.001), long-abstinence period (p < 0.001), without current polysubstance dependence (p < 0.001), and with treatment (p < 0.001) had increased risky decision-making when compared to the controls. On the other hand, elderly substance users with short-abstinence period showed increased risky decision-making. Moreover, current treatment status and polysubstance use may not influence the level of decision-making in substance users.

CONCLUSIONS

The results show that substance use is associated with impaired risky decision-making, indicating that interventions targeting risky decision-making in substance users should be developed for relapse prevention and rehabilitation.

Prevalence and risk factors for khat use among youth students in Ethiopia: systematic review and meta-analysis, 2018

BACKGROUND

Khat use is a widely spreading public health problem affecting the most economically productive population areas in Ethiopia. Khat use among students has been linked with mental, physical, social, and psychological problems. Reliable prevalence has not been recognized because of varying published rates. The objective of this systematic review and meta-analysis is to synthesize evidence on the prevalence and potential risk factors of khat use in Ethiopia.

METHODS

We found 284 studies of which 266 were removed due to duplication, irrelevant topics, and other reasons, respectively. All studies conducted in Ethiopia on khat chewing among students irrespective of time frame were included. Subsequently, 18 studies were used for synthesis of prevalence. Figures were extracted from published reports, and any lost information was requested from investigators. The quality of the included literature was evaluated by using the Newcastle-Ottawa Scale (NOS). Prevalence was pooled using random-effects meta-analyses. The presence of association was declared using P-values and an odds ratio with a corresponding 95% CI.

RESULTS

The pooled prevalence of khat use among students was 16.7% (13.7-19.7%). In the subgroup analysis, the highest prevalence was observed in the Oromia region, at 21.1% (15.5%, 26.7%), and an almost equal prevalence of 14.8% (10.6, 18.9) and 14.3% (10.3, 18.3) was observed in Amhara and the Southern Nation, Nationalities, and People's Region of Ethiopia, respectively. Being male (OR: 2.43 (1.73, 3.13)), being a Muslim religion follower (OR: 2.22 (1.6, 2.8)), being an alcohol user (OR: 2.3 (1.5, 3.0)), khat use by a family member (OR: 1.8 (1.4, 2.2)), peer pressure (OR: 4.4 (3.1, 5.6)), and being a cigarette smoker (OR: 8.5 (5.3, 11.7)) were found to be risk factors for khat chewing.

CONCLUSIONS

Khat use is a common problem among students. Health promotion, awareness on effect of khat, set policy on khat and substance use on the male sex, Muslim religion, alcohol user, having a family-member khat user, peer pressure, and being a cigarette smoker as possible risk factors for khat use among students.

LIMITATIONS

Irrespective of time restriction, all studies conducted in Ethiopia are included and cross-sectional in nature. Protocol no. CRD-42017081886.

Cognitive Training for the Treatment of Addictions Mediated by Information and Communication Technologies (ICT)

This work constitutes a narrative review of the state of knowledge and advances in the intervention and treatment of addictions through the use of information and communication technologies, considering the growing demand for virtuality-mediated strategies that facilitate the approach of problems of public health such as addictions, which increase considerably year after year. To this end, the reader will be provided with a current overview of the drug use trend; subsequently, a conceptualization of the concept of addiction and its understanding from a neurobiological perspective and, finally, the progress in terms of intervention processes and therapeutic approach will be presented; which will imply an approach to the concept of e-health and rehabilitation mediated by information and communication technologies (ICT).

Cell-type and projection-specific dopaminergic encoding of aversive stimuli in addiction

Drug addiction is a major public health concern across the world for which there are limited treatment options. In order to develop new therapies to correct the behavioral deficits that result from repeated drug use, we need to understand the neural circuit dysfunction that underlies the pathophysiology of the disorder. Because the initial reinforcing effects of drugs are dependent on increases in dopamine in reward-related brain regions such as the mesolimbic dopamine pathway, a large focus of addiction research has centered on the dysregulation of this system and its control of positive reinforcement and motivation. However, in addition to the processing of positive, rewarding stimuli, there are clear deficits in the encoding and valuation of information about potential negative outcomes and how they control decision making and motivation. Further, aversive stimuli can motivate or suppress behavior depending on the context in which they are encountered. We propose a model where rewarding and aversive information guides the execution of specific motivated actions through mesocortical and mesolimbic dopamine acting on D1- and D2- receptor containing neuronal populations. Volitional drug exposure alters the processing of rewarding and aversive stimuli through remodeling of these dopaminergic circuits, causing maladaptive drug seeking, self-administration in the face of negative consequences, and drug craving. Together, this review discusses the dysfunction of the circuits controlling different types of aversive learning as well as how these guide specific discrete behaviors, and provides a conceptual framework for how they should be considered in preclinical addiction models.

Compulsivity in Alcohol Use Disorder and Obsessive Compulsive Disorder: Implications for Neuromodulation

Alcohol use Disorder (AUD) is one of the leading causes of morbidity and mortality worldwide. The progression of the disorder is associated with the development of compulsive alcohol use, which in turn contributes to the high relapse rate and poor longer term functioning reported in most patients, even with treatment. While the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) defines AUD by a cluster of symptoms, parsing its heterogeneous phenotype by domains of behavior such as compulsivity may be a critical step to improve outcomes of this condition. Still, neurobiological underpinnings of compulsivity need to be fully elucidated in AUD in order to better design targeted treatment strategies. In this manuscript, we review and discuss findings supporting common mechanisms between AUD and OCD, dissecting the construct of compulsivity and focusing specifically on characteristic disruptions in habit learning and cognitive control in the two disorders. Finally, neuromodulatory interventions are proposed as a probe to test compulsivity as key pathophysiologic feature of AUD, and as a potential therapy for the subgroup of individuals with compulsive alcohol use, i.e., the more resistant stage of the disorder. This transdiagnostic approach may help to destigmatize the disorder, and suggest potential treatment targets across different conditions.

Prevalence of cognitive impairment in patients with substance use disorder

INTRODUCTION AND AIMS

Cognitive impairments in substance use disorder predict treatment outcome and are assumed to differ between substances. They often go undetected, thus the current study focuses on the prevalence of and differences in cognitive functioning across substances by means of a cognitive screen at the early stage of addiction treatment.

DESIGN AND METHODS

The Montreal Cognitive Assessment was administered to outpatients seeking treatment for substance use disorder. Patient characteristics (age, years of regular use, polysubstance use, severity of dependence/abuse, depression, anxiety and stress) were also taken into account.

RESULTS

A total of 656 patients were included (n = 391 used alcohol, n = 123 used cannabis, n = 100 used stimulants and n = 26 used opioids). The prevalence of cognitive impairments was 31%. Patients using alcohol had a lower total- and memory domain score than those using cannabis. Patients using opioids scored lower on visuospatial abilities than those using cannabis or stimulants. Younger patients scored higher than older patients. No effect was found for the other investigated characteristics.

DISCUSSION AND CONCLUSIONS

Given the high prevalence of cognitive impairments, standard screening at an early stage of treatment is important to determine the course of treatment and maximise treatment outcome. Caution is needed in interpreting results about opioids due to an underrepresentation of this patient group, and more research is needed on the effect of age on Montreal Cognitive Assessment performance.

Prevalence and associated factors of khat chewing among students in Ethiopia: a protocol for systematic review and meta-analysis

INTRODUCTION

These days, in Ethiopia, khat chewing is one of the widely spreading public health problems affecting the most productive segment of the population. The health implications of khat chewing among students are strongly linked with poor mental, physical and social performances. However, the national magnitude of khat chewing and the associated factors among Ethiopian students are unknown. Therefore, this systematic review and meta-analysis will answer the national prevalence of khat chewing and the associated factors among students in Ethiopia.

METHODS

Published primary relevant articles will be accessed using various databases, such as Medline, PubMed, EMBASE and Scopus. Other electronic search engines, for instance, Google Scholar and Google, will be used. Furthermore, additional studies will be collected by communicating with the author(s) and following the references of relevant articles. To select eligible studies, the Joanna Briggs Institute quality appraisal checklist will be used. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist will be followed to keep the scientific rigour of the study. Heterogeneity between studies will be examined through forest plot and I² heterogeneity tests. To identify influential studies, sensitivity analysis will be done. For substantial heterogeneity (I²>50%), the DerSimonian and Laird random-effects model will be employed. Subgroup analyses will be conducted using the random-effect model. Moreover, small studies' publication bias will be checked by funnel plots and objectively by Egger's regression test. If in case Egger's test was found to be statistically significant (p<0.05), trim and fill (Duval and Tweedie) analysis will be performed. The presence of association will be declared using p≤0.05 and OR with corresponding 95% CI.

ETHICS AND DISSEMINATION

Since the intention of the study is to describe earlier primary studies qualitatively and pool the results of those articles, ethical clearance will not be a concern. The results of the study will be published in a reputable peer-reviewed journal and presented at different scientific research conferences. It will also be disseminated to academic as well as other concerned institutions.

PROSPERO REGISTRATION NUMBER

CRD-42,017,081,886.

Let's Open the Decision-Making Umbrella: A Framework for Conceptualizing and Assessing Features of Impaired Decision Making in Addiction

Decision-making impairments play a pivotal role in the emergence and maintenance of addictive disorders. However, a sound conceptualization of decision making as an umbrella construct, encompassing its cognitive, affective, motivational, and physiological subcomponents, is still lacking. This prevents an efficient evaluation of the heterogeneity of decision-making impairments and the development of tailored treatment. This paper thus unfolds the various processes involved in decision making by adopting a critical approach of prominent dual- or triadic-process models, which postulate that decision making is influenced by the interplay of impulsive-automatic, reflective-controlled, and interoceptive processes. Our approach also focuses on social cognition processes, which play a crucial role in decision making and addictive disorders but were largely ignored in previous dual- or triadic-process models. We propose here a theoretical framework in which a range of coordinated processes are first identified on the basis of their theoretical and clinical relevance. Each selected process is then defined before reviewing available results underlining its role in addictive disorders (i.e., substance use, gambling, and gaming disorders). Laboratory tasks for measuring each process are also proposed, initiating a preliminary process-based decision-making assessment battery. This original approach may offer an especially informative view of the constitutive features of decision-making impairments in addiction. As prior research has implicated these features as risk factors for the development and maintenance of addictive disorders, our processual approach sets the scene for novel and transdiagnostic experimental and applied research avenues.

Time-dependent neuronal changes associated with craving in opioid dependence: an fMRI study

Relapse after initially successful treatment is a significant problem facing the treatment of opioid dependence. Evidence suggests craving elicited by re‐exposure to drug cues may precipitate relapse. Attempts to identify neural biomarkers of cue‐elicited craving have yielded inconsistent findings. We aimed to apply a novel continuous functional magnetic resonance imaging technique to follow the minute‐to‐minute evolution of brain responses, which correlate with the waxing and waning of craving. Newly detoxified male opioid‐dependent patients and healthy control participants attended two separate, counterbalanced, functional magnetic resonance imaging scanning sessions during which they viewed a 10‐minute video (drug cue or neutral cue) followed by 5 minutes of fixation. Participants rated the intensity of their craving throughout each session. We hypothesized that subcortical/ventral prefrontal cortex (PFC) regions and dorsal PFC regions would show different associations with craving reflecting their putative roles in appetitive processing versus cognitive control. Compared with controls, drug cue (minus neutral cue) video recruited the left amygdala and was temporally correlated with craving. In contrast, dorsal anterior cingulate blood‐oxygen‐level‐dependent signal time course was higher than controls only during a period after cue exposure when craving levels were declining. Against expectations, neither the ventral striatum nor ventral PFC was significantly recruited by drug cue exposure. Findings suggest that the amygdala has a central role in craving, whereas the dorsal anterior cingulate may control craving in treatment‐seeking patients. Time course analysis yielded new insights into the neural substrates of craving that could objectively validate development of psychological and pharmacological approaches to sustained abstinence.

Tobacco and cannabis use in college students are predicted by sex-dimorphic interactions between MAOA genotype and child abuse

BACKGROUND

Postsecondary students in Western countries exhibit a high prevalence of cannabis and tobacco use disorders. The etiology of these problems is contributed by several psychosocial factors, including childhood adversity and trauma; however, the mechanisms whereby these environmental determinants predispose to the use of these substances remain elusive, due to our poor knowledge of genetic and biological moderators. Converging evidence points to the monoamine oxidase A (MAOA) gene as a moderator of the effects of lifetime stress on the initiation of substance use.

AIMS

Building on these premises, in this study, we analyzed whether MAOA upstream variable number tandem repeat (uVNTR) alleles interact with child maltreatment history to predict for lifetime cannabis and tobacco consumption.

MATERIALS AND METHODS

Five hundred college students (age: 18-25 years) from a large Midwestern University were surveyed for their child maltreatment history (encompassing emotional, physical, and sexual abuse, as well as emotional and physical neglect) and lifetime consumption of cannabis and tobacco. Saliva samples were obtained to determine the MAOA uVNTR genotype of each participant.

RESULTS

In female students, lifetime tobacco and cannabis use was predicted by the interaction of physical and emotional abuse with high-activity MAOA allelic variants; conversely, in males, the interaction of low-activity MAOA alleles and physical abuse was associated with lifetime use of tobacco, but not cannabis.

DISCUSSION

These findings collectively suggest that the vulnerability to smoke tobacco and cannabis is predicted by sex-dimorphic interactions of MAOA gene with childhood abuse.

CONCLUSION

These biosocial underpinnings of tobacco and cannabis use may prove important in the development of novel personalized preventive strategies for substance use disorders in adolescents.

Cognitive deficits in problematic drinkers with and without mild to borderline intellectual disability

We examined cognitive deficits in problematic drinkers with and without mild to borderline intellectual disability (MBID). Problematic drinkers were expected to show a significantly lower estimated performance IQ (PIQ), but not a lower estimated verbal IQ (VIQ), compared to light drinkers. Participants ( N = 474) were divided into four groups based on IQ and severity of alcohol use-related problems. IQ was estimated using (a short form of) the Wechsler Adult Intelligence Scale third edition. Severity of alcohol use-related problems was assessed using the Alcohol Use Disorder Identification Test. Overall, there were no significant differences between light and problematic drinkers on estimated VIQ. Within the group without MBID, estimated PIQ was significantly lower. Estimated PIQ was not lower in problematic drinkers with MBID compared to light drinkers with MBID. The results are indicative of cognitive deficits in problematic drinkers without MBID. Screening for cognitive deficits with additional instruments is advised.

Aberrant regional brain activities in alcohol dependence: a functional magnetic resonance imaging study

OBJECTIVE

Whether moderate alcohol consumption has health benefits remains controversial, but the harmful effects of excessive alcohol consumption on behavior and brain function are well recognized. The aim of this study was to investigate alcohol-induced regional brain activities and their relationships with behavioral factors.

SUBJECTS AND METHODS

A total of 29 alcohol-dependent subjects (9 females and 20 males) and 29 status-matched healthy controls (11 females and 18 males) were recruited. Severity of alcohol dependence questionnaire (SADQ) and alcohol use disorders identification test (AUDIT) were used to evaluate the severity of alcohol craving. Regional homogeneity (ReHo) analysis was used to explore the alcohol-induced regional brain changes. Receiver operating characteristic (ROC) curve was used to investigate the ability of regional brain activities to distinguish alcohol-dependent subjects from healthy controls. Pearson correlations were used to investigate the relationships between alcohol-induced ReHo differences and behavioral factors.

RESULTS

Alcohol-dependent subjects related to healthy controls showed higher ReHo areas in the right superior frontal gyrus (SFG), bilateral medial frontal gyrus (MFG), left precentral gyrus (PG), bilateral middle temporal gyrus (MTG), and right inferior temporal gyrus (ITG) and lower ReHo areas in the right cerebellum posterior lobe (CPL), left rectal gyrus (RG), and right cluster of pons and cerebellum anterior lobe (CAL). ROC curve revealed high area under the curve (AUC) values (mean ± SD: 0.864 ± 0.028; range: 0.828-0.911) of ReHo differences. Diagnostic analysis showed that these areas alone discriminated alcohol-dependent subjects from healthy controls with high degree of sensitivities (mean ± SD: 81.25% ± 11.49%; range: 62.5%-100%) and specificities (mean ± SD: 81.75% ± 12.36%; range: 67.5%-100%). Years of drink showed negative correlation with left RG (r = -0.493, p = 0.007), the same finding was shown between AUDIT and right CPL (r = -0.52, p = 0.004).

CONCLUSION

Alcohol dependence is associated with aberrant regional activities in multiple brain areas. ReHo analysis may be a useful biological indicator for the detection of regional brain activities in individuals with alcohol dependence.

Error detection and behavioural inhibition in young heavy drinkers

BACKGROUND

Increases in inhibitory errors in heavy drinkers are established; less well-studied is whether heavy drinkers are aware of these errors in performance. Reductions in error detection and awareness limit the possibility for remedial action to be taken, and have implications for substance abusers seeking to control use: failure to monitor and/or adjust ongoing behaviour may be linked to using more or more often than intended, and failing to adjust behaviour after a slip. Here we report the first study of both inhibitory control and error awareness in young heavy drinkers, using behavioural and psychophysiological measures.

METHODS

Heavy drinkers (n=25) and light- or non-drinking controls (n=35) completed a difficult inhibitory task which required signaling the awareness of inhibitory errors on the subsequent trial, while brain electrical activity was recorded.

RESULTS

Heavy drinkers made more inhibitory errors than controls, but we observed no difference in error awareness, both via overt signaling and with equivalent amplitude of the error positivity (Pe), indexing conscious error detection. Similarly, controls and heavy drinkers showed no difference in amplitude or latency of the error-related negativity (ERN), indexing early pre-conscious error detection.

CONCLUSIONS

This research suggests no significant difference in detection of errors in heavy drinkers, even as they are more prone to make these errors, a result seen in dependent drinkers reported elsewhere. Future research with larger sample sizes, and a more difficult task producing sufficient errors, should determine whether heavy drinkers employ sufficient post-error remedial action.

Abnormal intrinsic functional hubs in alcohol dependence: evidence from a voxelwise degree centrality analysis

OBJECTIVE

To explore the abnormal intrinsic functional hubs in alcohol dependence using voxelwise degree centrality analysis approach, and their relationships with clinical features.

MATERIALS AND METHODS

Twenty-four male alcohol dependence subjects free of medicine (mean age, 50.21±9.62 years) and 24 age- and education-matched male healthy controls (mean age, 50.29±8.92 years) were recruited. The alcohol use disorders identification test and the severity of alcohol dependence questionnaire (SADQ) were administered to assess the severity of alcohol craving. Voxelwise degree centrality approach was used to assess the abnormal intrinsic functional hubs features in alcohol dependence. Simple linear regression analysis was performed to investigate the relationships between the clinical features and abnormal intrinsic functional hubs.

RESULTS

Compared with healthy controls, alcohol dependence subjects exhibited significantly different degree centrality values in widespread left lateralization brain areas, including higher degree centrality values in the left precentral gyrus (BA 6), right hippocampus (BA 35, 36), and left orbitofrontal cortex (BA 11) and lower degree centrality values in the left cerebellum posterior lobe, bilateral secondary visual network (BA 18), and left precuneus (BA 7, 19). SADQ revealed a negative linear correlation with the degree centrality value in the left precentral gyrus (R²=0.296, P=0.006).

CONCLUSION

The specific abnormal intrinsic functional hubs appear to be disrupted by alcohol intoxication, which implicates at least three principal neural systems: including cerebellar, executive control, and visual cortex, which may further affect the normal motor behavior such as an explicit type of impaired driving behavior. These findings expand our understanding of the functional characteristics of alcohol dependence and may provide a new insight into the understanding of the dysfunction and pathophysiology of alcohol dependence.

Brain function during cognitive flexibility and white matter integrity in alcohol-dependent patients, problematic drinkers and healthy controls

Cognitive flexibility has been associated with prefrontal white matter (WM) integrity in healthy controls (HCs), showing that lower WM integrity is associated with worse performance. Although both cognitive flexibility and WM integrity have been found to be aberrant in alcohol-dependent (AD) patients, the relationship between the two has never been tested. In this study, we investigated the association between WM tract density and cognitive flexibility in patients with AD (n = 26) and HCs (n = 22). In order to assess the influence of AD severity, we also included a group of problematic drinkers (PrDs; n = 23) who did not meet the AD criteria. Behavioral responses and brain activity during a cognitive flexibility task were measured during functional magnetic resonance imaging. Probabilistic fiber tracking was performed between the dorsolateral prefrontal cortex and the basal ganglia; two crucial regions for task switching. Finally, the task-related functional connectivity between these areas was assessed. There were no significant group differences in the task performance. However, compared with HCs, AD patients and PrDs showed decreased WM integrity and increased prefrontal brain activation during task switching. Evidence is presented for a compensatory mechanism, involving recruitment of additional prefrontal resources in order to compensate for WM and neural function impairments in AD patients and PrDs. Although present in both alcohol groups, the PrDs were more successful in invoking this compensatory mechanism when compared to the AD patients. We propose that this may therefore serve as a protective factor, precluding transition from problematic drinking into alcohol dependence.

Imaging the D3 dopamine receptor across behavioral and drug addictions: Positron emission tomography studies with [(11)C]-(+)-PHNO

Chronic drug use has been associated with dopaminergic abnormalities, detectable in humans with positron emission tomography (PET). Among these, a hallmark feature is low D2 dopamine receptor availability, which has been linked to clinical outcomes, but has not yet translated into a therapeutic strategy. The D3 dopamine receptor on the other hand has gained increasing attention, as, in contrast to D2, chronic exposure to drugs has been shown to up-regulate this receptor subtype in preclinical models of addiction-a phenomenon linked to dopamine system sensitization and drug-seeking. The present article summarizes the literature to date in humans, suggesting that the D3 receptor may indeed contribute to core features of addiction such as impulsiveness and cognitive impairment. A particularly useful tool in investigating this question is the PET imaging probe [(11)C]-(+)-PHNO, which binds to D2/3 dopamine receptors but has preferential affinity for D3. This technique has been used to demonstrate D3 up-regulation in humans, and can be applied to assess pharmacological interventions for development of D3-targeted strategies in addiction treatment.

Performance of Smokers with DSM-5 Tobacco Use Disorder in Time-Based Complex Prospective Memory

Studies that investigate time-based complex prospective memory (PM) functioning in participants with substance use disorders (SUD) in consideration of different PM-phases (planning, retention, initiation, execution) are lacking. This study was designed to investigate performance of young adults with DSM-5 tobacco use disorder (TUD) and healthy controls (HC) in different phases of complex PM. Community participants aged 18-35 (N=43) completed the modified Six Elements Test that includes the PM-phases planning, retention, initiation, and execution of a time-based complex PM-task (with delay phases and background activities). TUD participants were current daily smokers and fulfilled at least two DSM-5 TUD criteria. TUD did not differ significantly from HC in task planning errors and timely task initiation. No group differences showed in rule adherence and completeness during task conduction (execution). During execution, TUD showed significantly more deviations (Coef. 0.45; p=0.005) from their originally remembered plans than HC. Young adults with relatively mild TUD do not show general impairments in all phases of short-term, complex, and time-based PM. Future research may investigate whether a greater risk of deviation from originally remembered plans in TUD could play a role in the progression and cessation of smoking behavior.

Bridging the gap between the neurocognitive lab and the addiction clinic

In the past decennium there has been an enormous increase in new insights in cognitive mechanisms of addiction and their neural substrates. These candidate neurocognitive mechanisms, particularly those associated with "drive" and "control" aspects of addiction, are clearly involved in substance use problems but do not yet provide a full explanation. The neurocognitive mechanisms addressed in the present perspective are attentional bias, reward processing (both drive aspects) and error-processing and cognitive control (both control aspects). The time has come to transfer these recent insights more consistently to clinical practice by studying their relevance for diagnosis and treatment in patient samples. The present perspective echoes the development of recent initiatives such as the RDoC system to integrate developments in neuroscience into clinical practice. The aim of this article is to open new vistas for addiction diagnosis and treatment and to discuss why and how these neurocognitive aspects of addictive behavior can be used in clinical practice. In addition, present problematic issues and a future research agenda are provided.

Differences in functional connectivity between alcohol dependence and internet gaming disorder

INTRODUCTION

Internet gaming disorder (IGD) and alcohol dependence (AD) have been reported to share clinical characteristics including craving and over-engagement despite negative consequences. However, there are also clinical factors that differ between individuals with IGD and those with AD in terms of chemical intoxication, prevalence age, and visual and auditory stimulation.

METHODS

We assessed brain functional connectivity within the prefrontal, striatum, and temporal lobe in 15 patients with IGD and in 16 patients with AD. Symptoms of depression, anxiety, and the attention deficit hyperactivity disorder were assessed in patients with IGD and in patients with AD.

RESULTS

Both AD and IGD subjects have positive functional connectivity between the dorsolateral prefrontal cortex (DLPFC), cingulate, and cerebellum. In addition, both groups have negative functional connectivity between the DLPFC and the orbitofrontal cortex. However, the AD subjects have positive functional connectivity between the DLPFC, temporal lobe and striatal areas while IGD subjects have negative functional connectivity between the DLPFC, temporal lobe and striatal areas.

CONCLUSIONS

AD and IGD subjects may share deficits in executive function, including problems with self-control and adaptive responding. However, the negative connectivity between the DLPFC and the striatal areas in IGD subjects, different from the connectivity observed in AD subjects, may be due to the earlier prevalence age, different comorbid diseases as well as visual and auditory stimulation.

Deficits in behavioural inhibition in substance abuse and addiction: a meta-analysis

AIMS

Deficits in behavioural inhibitory control are attracting increasing attention as a factor behind the development and maintenance of substance dependence. However, evidence for such a deficit is varied in the literature. Here, we synthesised published results to determine whether inhibitory ability is reliably impaired in substance users compared to controls.

METHODS

The meta-analysis used fixed-effects models to integrate results from 97 studies that compared groups with heavy substance use or addiction-like behaviours with healthy control participants on two experimental paradigms commonly used to assess response inhibition: the Go/NoGo task, and the Stop-Signal Task (SST). The primary measures of interest were commission errors to NoGo stimuli and stop-signal reaction time in the SST. Additionally, we examined omission errors to Go stimuli, and reaction time in both tasks. Because inhibition is more difficult when inhibition is required infrequently, we considered papers with rare and equiprobable NoGo stimuli separately.

RESULTS

Inhibitory deficits were apparent for heavy use/dependence on cocaine, MDMA, methamphetamine, tobacco, and alcohol (and, to a lesser extent, non-dependent heavy drinkers), and in pathological gamblers. On the other hand, no evidence for an inhibitory deficit was observed for opioids or cannabis, and contradictory evidence was observed for internet addiction.

CONCLUSIONS

The results are generally consistent with the view that substance use disorders and addiction-like behavioural disorders are associated with impairments in inhibitory control. Implications for treatment of substance use are discussed, along with suggestions for future research arising from the limitations of the extant literature.

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.

Optimal neurocognitive, personality and behavioral measures for assessing impulsivity in cocaine dependence

BACKGROUND

Impulsivity may underlie the poor treatment retention and high relapse rates observed in cocaine-dependent persons. However, observed differences in measures of impulsivity between cocaine-dependent and healthy control participants often do not reach clinical significance, suggesting that the clinical relevance of these differences may be limited.

OBJECTIVES

To examine which measures of impulsivity (i.e. self-report impulsivity, self-report personality, neurocognitive testing) best distinguish cocaine-dependent and healthy control participants (i.e. showing differences at least 1.5 standard deviations [SD] from controls). Optimal measures were considered to demonstrate sufficient classification accuracy.

METHODS

Sixty-five recently abstinent cocaine-dependent and 25 healthy control participants were assessed using select neurocognitive tests and self-report questionnaires including the NEO Personality Inventory-Revised (NEO-PI-R), Temperament and Character Inventory (TCI), Barratt Impulsiveness Scale (BIS-11a), and the Frontal Systems Behavior Scale (FrSBe).

RESULTS

When corrected for years of education and gender, neurocognitive measures did not demonstrate clinically significant differences between cocaine-dependent and control participants. The personality measures TCI Purposefulness and Congruent Second Nature and NEO-PI-R Impulsiveness, and the self-rating measures FrSBe Disinhibition and BIS-11 Motor Impulsivity and Total successfully identified clinically meaningful elevations in impulsivity within cocaine-dependent participants (>1.5 SDs from controls). Furthermore, these measures achieved 84-93% accuracy in discriminating cocaine-dependent from control participants.

CONCLUSION

Clinically significant neurocognitive impairment in cocaine-dependent participants was not observed in this sample. As the BIS-11 or FrSBe are brief to administer, accurate, and have been shown to predict treatment retention and relapse, these measures appear to be optimal, relative to the personality measures, for examining trait impulsivity in cocaine dependence.

New perspectives on using brain imaging to study CNS stimulants

While the recent application of brain imaging to study CNS stimulants has offered new insights into the fundamental factors that contribute to their use and abuse, many gaps remain. Brain circuits that mediate pleasure, dependence, craving and relapse are anatomically, neurophysiologically and neurochemically distinct from one another, which has guided the search for correlates of stimulant-seeking and taking behavior. However, unlike other drugs of abuse, metrics for tolerance and physical dependence on stimulants are not obvious. The dopamine theory of stimulant abuse does not sufficiently explain this disorder as serotonergic, GABAergic and glutamagergic circuits are clearly involved in stimulant pharmacology and so tracking the source of the "addictive" processes must adopt a more multimodal, multidisciplinary approach. To this end, both anatomical and functional magnetic resonance imaging (MRI), MR spectroscopy (MRS) and positron emission tomography (PET) are complementary and have equally contributed to our understanding of how stimulants affect the brain and behavior. New vistas in this area include nanotechnology approaches to deliver small molecules to receptors and use MRI to resolve receptor dynamics. Anatomical and blood flow imaging has yielded data showing that cognitive enhancers might be useful adjuncts in treating CNS stimulant dependence, while MRS has opened opportunities to examine the brain's readiness to accept treatment as GABA tone normalizes after detoxification. A desired outcome of the above approaches is being able to offer evidence-based rationales for treatment approaches that can be implemented in a more broad geographic area, where access to brain imaging facilities may be limited. This article is part of the Special Issue entitled 'CNS Stimulants'.

Volumetric differences in the anterior cingulate cortex prospectively predict alcohol-related problems in adolescence

RATIONALE

Individual differences in brain structure and function are suggested to exist prior to the onset of alcohol abuse. Cross-sectional studies have demonstrated abnormalities in brain regions underlying affective processes that may form a pathway to the emergence of later alcohol abuse and dependence in vulnerable individuals. However, no prospective studies have examined whether these abnormalities predict later problems with alcohol.

OBJECTIVE

This study aims to examine whether individual differences in affect and brain volume prospectively predict alcohol-related problems in adolescence.

METHOD

Adolescent drinkers (n = 98) were recruited from an ongoing prospective, longitudinal study examining adolescent emotional development. At age 12, participants underwent structural magnetic resonance imaging to obtain volumetric data on the amygdala, hippocampus, orbitofrontal cortex, and anterior cingulate cortex (ACC), and completed a self-report measure of affective temperament. At age 16, participants completed a questionnaire measuring alcohol use, with 39 % reporting alcohol-related problems in the past year.

RESULTS

Pre-existing differences in the left ACC predicted problem drinking. Alcohol-related problems were associated with higher levels of temperamental negative affectivity; however, these were not correlated with anterior cingulate volumes.

CONCLUSIONS

These findings indicate that individual differences in the structural morphology of the anterior cingulate, a region implicated in affective processes, self-control, and drug addiction, predict later alcohol-related problems. Although this finding remained significant after controlling for other substance use and psychopathology, future research is required to test its specificity for alcohol use disorders.

Current hypotheses on the mechanisms of alcoholism

Chronic use of alcohol results in progressive changes to brain and behavior that often lead to the development of alcohol dependence and alcoholism. Although the mechanisms underlying the development of alcoholism remain to be fully elucidated, diminished executive functioning due to hypoactive prefrontal cortex executive control and hyperactive limbic system anxiety and negative emotion might contribute mechanistically to the shift from experimental use to alcoholism and dependence. In the chapter that follows, behavioral deficits associated with cortical dysfunction and neurodegeneration will be related to the behavioral characteristics of alcoholism (e.g., diminished executive function, impulsivity, altered limbic modulation). We will provide evidence that alterations in cyclic AMP-responsive element binding protein (CREB: neurotrophic) and NF-κB (neuroimmune) signaling contribute to the development and persistence of alcoholism. In addition, genetic predispositions and an earlier age of drinking onset will be discussed as contributing factors to the development of alcohol dependence and alcoholism. Overall chronic ethanol-induced neuroimmune gene induction is proposed to alter limbic and frontal neuronal networks contributing to the development and persistence of alcoholism.

Evidence of deficits in behavioural inhibition and performance monitoring in young female heavy drinkers

BACKGROUND

New models of the development and maintenance of substance abuse give increasing importance to the role of deficits in inhibitory function. Much of the evidence to support this claim comes from male participants, despite some researchers showing greater disinhibition in females. Clearly, more research on female heavy drinkers is warranted. In this study, we examine behavioural and psychophysiological measures of inhibitory function in female young adults who do and do not regularly drink heavily.

METHODS

Participants were thirty female young adults (aged 18-21) who drink heavily (four or more standard drinks per occasion) at least once a month (n=13) or who drink heavily less often than this (n=17); none regularly used any other drugs, including tobacco. They underwent interviews assessing prior use of alcohol, before completing a stop-signal task while brain electrical activity was recorded.

RESULTS

Regular heavy drinkers displayed a longer stop-signal reaction time (the time required to stop an inappropriate response), and a larger P3 increase for successful compared to failed inhibition trials. Heavy drinkers also displayed a smaller error-related negativity (ERN) amplitude, indexing a deficit in performance monitoring.

CONCLUSION

These results indicate that large deficits in inhibitory processing and performance monitoring occur in young female heavy drinkers, and that heavy drinkers may have to work harder in order to successfully inhibit a response. Future research may determine whether these deficits pre-date or are caused by alcohol abuse.

Modulation of the endocannabinoid system: vulnerability factor and new treatment target for stimulant addiction

Cannabis is one of the most widely used illicit substance among users of stimulants such as cocaine and amphetamines. Interestingly, increasing recent evidence points toward the involvement of the endocannabinoid system (ECBS) in the neurobiological processes related to stimulant addiction. This article presents an up-to-date review with deep insights into the pivotal role of the ECBS in the neurobiology of stimulant addiction and the effects of its modulation on addictive behaviors. This article aims to: (1) review the role of cannabis use and ECBS modulation in the neurobiological substrates of psychostimulant addiction and (2) evaluate the potential of cannabinoid-based pharmacological strategies to treat stimulant addiction. A growing number of studies support a critical role of the ECBS and its modulation by synthetic or natural cannabinoids in various neurobiological and behavioral aspects of stimulants addiction. Thus, cannabinoids modulate brain reward systems closely involved in stimulants addiction, and provide further evidence that the cannabinoid system could be explored as a potential drug discovery target for treating addiction across different classes of stimulants.

Alcohol Consumption and Executive Functions in Adolescents: A Systematic Review

Objetivo: el consumo de alcohol entre los estudiantes universitarios se ha convertido en una preocupación creciente en los últimosaños, por lo que este estudio fue desarrollado con el objetivo de identificar el consumo de esta sustancia entre los estudiantes de enfermería.Método: se trata de un estudio transversal desarrollado en una universidad privada en la ciudad de Río de Janeiro, Brasil, con 161estudiantes que respondieron a un cuestionario autoadministrado que contiene información sociodemográfica, preguntas seleccionadasdel Alcohol Use Disorders Identification Test y otros aspectos relacionados con el consumo de bebidas alcohólicas. Resultados: alta proporción(67,7 %) de los estudiantes de enfermería entrevistados reportó ser consumidores de alcohol, y el 32,1 % de ellos estaban en laorgía de consumo estándar, y casi la mitad (45,9 %) de los consumidores están expuestos al riesgo de desarrollar problemas relacionadoscon el consumo de esta sustancia. Resultados: están preocupados por el consumo de bebidas alcohólicas de los estudiantes de enfermeríaque participaron en este estudio, ya que son los futuros profesionales que inevitablemente actúan como educadores y motivadorespara la adopción de conductas saludables en la población. Conclusión: por lo tanto, se necesitan políticas y programas para prevenir elconsumo excesivo de alcohol en esta población.

Working memory and impulsivity predict marijuana-related problems among frequent users

BACKGROUND

Although marijuana is the most commonly used illicit substance in the US, only a small portion of users go on to develop dependence, suggesting that there are substantial individual differences in vulnerability to marijuana-related problems among users. Deficits in working memory and high trait impulsivity are two factors that may place marijuana users at increased risk for experiencing related problems.

METHODS

Using baseline data from an experimental study that recruited 104 frequent marijuana users (M=71.86% of prior 60 days, SD=22%), we examined the associations of working memory and trait impulsivity with marijuana-related problems.

RESULTS

Lower working memory, as measured by Trail Making Test B, but not short-term memory capacity, predicted more marijuana-related problems. Higher trait impulsivity scores were independently associated with greater number of problems.

CONCLUSIONS

Results suggest that marijuana users with reduced executive cognitive ability are more susceptible to developing problems related to their use. Trait impulsivity and executive working memory appear to be independent risk factors for experiencing marijuana-related problems.

Decision-making deficits are still present in heroin abusers after short- to long-term abstinence

BACKGROUND

Substance dependent individuals (SDIs) consistently show deficits in decision making with biased choices toward immediate rewards, even at the expense of future consequences. However, relatively little evidence has been reported concerning the population of drug abusers who are exclusively addicted to heroin.

METHODS

The present study tested 124 male abstinent "pure" heroin (AH) abusers (divided into short-term, mid-term, and long-term groups based on their length of abstinence) and 43 healthy controls (HC) intending to address this issue. Two decision-making tasks, the Delay Discounting Task (DDT) and the Iowa Gambling Task (IGT) were employed to measure their decision-making performance.

RESULTS

Compared to HC participants, AH participants made significantly poorer choices on both the DDT and the IGT and the poor decision-making performances were not influenced by their lengths of abstinence. It is suggested that heroin-abuse-related decision-making deficits that are demonstrated by rapidly discounting future rewards; preferring incentives with large short-term gains while ignoring accompanying potential risks; and being inflexible in adjusting decision-making behaviors in accordance with outcome feedback, may not be compensated for even after a long period of abstinence from heroin abuse.

CONCLUSION

Hence, this inability to recover should be taken into consideration in the evaluation, prevention and intervention of heroin abuse and relapse.