Understanding drug addiction: a neuropsychological perspective

Neuropsychological functioning is compromised in binge drinking young adults with depression

For many young people, binge drinking is the most common form of alcohol misuse, particularly in those with a depressive disorder. Nonetheless, relatively little is known about the effects that the combination of depression and binge drinking has on neuropsychological outcomes. This study aimed to determine whether binge drinkers with depression show more pronounced neuropsychological dysfunction compared to their peers with depression alone or binge drinking alone. Neuropsychological testing was conducted on help-seeking young people (18-30 years) recently diagnosed with a depressive disorder and classified as either 'binge drinkers' (n=43) or 'non-bingers' (n=48). Two healthy control groups (i.e. binge drinkers, n=24 and non-bingers, n=21) were additionally recruited and also underwent the same testing. Qualitatively, binge-drinking patients with depression performed consistently below controls, depression alone, or binge drinking alone. In keeping with our hypotheses, visual learning and memory was significantly reduced in depressed binge drinkers, whereas mental flexibility was reduced at a trend level. There were no significant differences in neuropsychological performance in depressed alone or binge drinking alone individuals compared to controls. The findings suggest that when treating young people with a depressive disorder, strategies targeting binge drinking may contribute to preventing potential neurobiological changes underlying poorer long-term clinical outcomes.

The Teenage Brain

In this article, we explore the emerging and potential influence of adolescent brain science on law and public policy. The primary importance of this research is in policy domains that implicate adolescent risk taking; these include drug and alcohol use, driver licensing, and criminal justice. We describe the emerging importance of brain science in the Supreme Court and other policy arenas. Finally, we argue that current research cannot contribute usefully to legal decisions about individual adolescents and should not be used in criminal trials at the present time, except to provide general developmental information.

Stimulant use disorders: characteristics and comorbidity in an Australian population sample

OBJECTIVE

To describe the correlates of stimulant use disorders (abuse, dependence) in an Australian population sample, to compare the characteristics of stimulant users with and without stimulant use disorders and to describe the patterns of service use and help-seeking in people with stimulant use disorders.

METHODS

Data were drawn from the 2007 National Survey of Mental Health and Wellbeing, which sampled 8841 residents of private dwellings in Australia in 2007. Lifetime DSM-IV substance use and mental disorder diagnoses were obtained from interviews conducted by lay interviewers, using the Composite International Diagnostic Interview (CIDI). Socio-demographic, socio-economic and clinical correlates of stimulant use disorders were identified using binary logistic regression models. Stimulant users with and without stimulant use disorders were compared to non-stimulant users via multinomial logistic regression models.

RESULTS

Compared to Australians without stimulant use disorder, people with stimulant use disorders were younger, more likely to be male, of non-heterosexual orientation and born in Australia, but were not more socially disadvantaged. Lifetime comorbidity rates were high: 79% of persons with stimulant use disorders had a lifetime alcohol use disorder, 73% a lifetime cannabis use disorder, and more than one third a lifetime mood or anxiety disorder. Stimulant use disorders were associated with a family history of substance use, affective disorders and psychosis. One in five people with lifetime stimulant use disorders had been imprisoned, homeless or hospitalised for substance or mental health problems, and 13% reported at least one symptom of psychosis. Nearly half had sought help for substance or mental health problems, primarily from General Practitioners (GPs), psychologists or psychiatrists.

CONCLUSIONS

Stimulant use disorders in a representative population sample are associated with significant comorbidity and harm. Many persons with stimulant use disorders had sought care and found this helpful. There is scope for screening and intervention in this group.

A common TPH2 haplotype regulates the neural processing of a cognitive control demand

The monoamine neurotransmitter, serotonin, critically regulates the function of the cerebral cortex and is involved in psychiatric disorders. Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in the synthesis of serotonin with the neuron-specific TPH2 isoform present exclusively in the brain and encoded by the TPH2 gene on chromosome 12q21. The haplotype structure of TPH2 was defined for 16 single-nucleotide polymorphisms (SNPs) in a healthy subject population and a haplotype block analysis confirmed the presence of a six SNP haplotype in a yin configuration that has previously been associated with risk for suicidality, depression, and anxiety disorders. Functional magnetic resonance imaging (fMRI) was used to assess the influence of TPH2 variation on brain function related to cognitive control using the Multi-Source Interference Task (MSIT). The MSIT-related blood oxygen level-dependent (BOLD) response was increased with increasing copies of the TPH2 yin haplotype for the dorsal anterior cingulate cortex (dACC), right inferior frontal cortex (IFC), and anterior striatum. A functional connectivity analysis further revealed that increasing numbers of the TPH2 yin haplotype was associated with diminished functional coupling between the dACC and the right IFC, precentral gyrus, parietal cortex and dlPFC. A moderation analysis indicated that the relationship between neural processing networks and cognitive control was significantly modulated by allelic variation for the TPH2 yin haplotype. These findings suggest that the association of risk for psychiatric disorders with a common TPH2 yin haplotype is related to the inefficient functional engagement of cortical areas involved in cognitive control and alterations in the mode of functional connectivity of dACC pathways.

Improving control over the impulse for reward: sensitivity of harmful alcohol drinkers to delayed reward but not immediate punishment

BACKGROUND

Cognitive control dysfunction has been identified in dependent alcohol users and implicated in the transition from abuse to dependence, although evidence of dyscontrol in chronic but non-dependent 'harmful' alcohol abusers is mixed. The current study examined harmful alcohol users response inhibition over rewarding stimuli in the presence of monetary reward and punishment, to determine whether changes in sensitivity to these factors, noted in imaging studies of dependent users, influences impulse control.

METHOD

Harmful (n=30) and non-hazardous (n=55) alcohol users were administered a Monetary Incentive Go/No-go task that required participants to inhibit a prepotent motor response associated with reward.

RESULTS

Harmful alcohol users showed a significantly poorer ability to withhold their impulse for a rewarding stimulus in the presence of immediate monetary punishment for failure, while retaining equivalent response inhibition performance under neutral conditions (associated with neither monetary loss or gain), and significantly better performance under delayed reward conditions.

CONCLUSIONS

The results of the present study suggest that non-dependent alcohol abusers have altered sensitivity to reward and punishment that influences their impulse control for reward, in the absence of gross dyscontrol that is consistent with past findings in which such performance contingencies were not used. The ability of delayed monetary reward, but not punishment, to increase sustained impulse control in this sample has implications for the mechanism that might underlie the transition from alcohol abuse to dependence, as well as intervention strategies aimed at preventing this transition.

Personality, psychopathology, life attitudes and neuropsychological performance among ritual users of Ayahuasca: a longitudinal study

Ayahuasca is an Amazonian psychoactive plant beverage containing the serotonergic 5-HT_2A agonist N,N-dimethyltryptamine (DMT) and monoamine oxidase-inhibiting alkaloids (harmine, harmaline and tetrahydroharmine) that render it orally active. Ayahuasca ingestion is a central feature in several Brazilian syncretic churches that have expanded their activities to urban Brazil, Europe and North America. Members of these groups typically ingest ayahuasca at least twice per month. Prior research has shown that acute ayahuasca increases blood flow in prefrontal and temporal brain regions and that it elicits intense modifications in thought processes, perception and emotion. However, regular ayahuasca use does not seem to induce the pattern of addiction-related problems that characterize drugs of abuse. To study the impact of repeated ayahuasca use on general psychological well-being, mental health and cognition, here we assessed personality, psychopathology, life attitudes and neuropsychological performance in regular ayahuasca users (n = 127) and controls (n = 115) at baseline and 1 year later. Controls were actively participating in non-ayahuasca religions. Users showed higher Reward Dependence and Self-Transcendence and lower Harm Avoidance and Self-Directedness. They scored significantly lower on all psychopathology measures, showed better performance on the Stroop test, the Wisconsin Card Sorting Test and the Letter-Number Sequencing task from the WAIS-III, and better scores on the Frontal Systems Behavior Scale. Analysis of life attitudes showed higher scores on the Spiritual Orientation Inventory, the Purpose in Life Test and the Psychosocial Well-Being test. Despite the lower number of participants available at follow-up, overall differences with controls were maintained one year later. In conclusion, we found no evidence of psychological maladjustment, mental health deterioration or cognitive impairment in the ayahuasca-using group.

Determinants of inhalant (whitener) use among street children in a South Indian city

A cross-sectional study was conducted in the year 2008 among 174 children in observation homes in Hyderabad, India, to estimate the distribution of inhalant (whitener) use among this population. Data were collected using an instrument developed for this purpose. About 61% of the children were boys and their mean age was 12.2 years (range 5-18 years). Whitener use was found in 35% of the children along with concurrent use of other substances. Peer pressure was the commonest cause reported for initiating substance use. The high prevalence is an important concern for the Indian policymakers given the large number of street children in Indian cities.

A comparative study of the effects of methamphetamine on memory in existing and recovering addicts from a South African population

Memory is a complex of systems by which an organism registers, stores and retrieves exposure to an event or experience. Literature purports that methamphetamine users and dependents have been found to exhibits signs of memory impairment. The aim of the research was to establish the possible existence of significant differences in memory in current methamphetamine users, recovering methamphetamine users, and a matched drug naïve control group. Cognitive functioning was assessed via a neurocognitive test battery that examined the memory of 14 current methamphetamine users, 17 recovering methamphetamine addicts, and 18 drug naïve control participants who were matched according to the demographic variables of age, gender and educational status. The results indicated that recovering methamphetamine users experienced the greatest impairment in memory in comparison to both the control group and current users of methamphetamine. The current users of methamphetamine also experienced some impairment in memory functioning in visual acquisition and retention. The poor performance of the recovering addicts is explained by the juxtaposition of the stimulating and supplemental effect of methamphetamine as experienced by the current users versus the neurotransmitter depletion and structural changes in the brain experienced by the recovering addicts. The control group showed a superior performance since they did not suffer from the neurotoxic effects of methamphetamine.OpsommingGeheue is ‘n komplekse sisteem wat ‘n individu in staat stel om blootstelling aan ‘n voorval of ervarings te registreer, stoor, behou en herroep. Leer- en geheueprobleme is van die mees algemene simptome van neurosielkundige uitvalle in neurologiese en psigiatriese pasiënte. Die literatuur dui aan dat metamfetamienafhanklike verbruikers tipies geheuedisfunksie ervaar. Die doel van die navorsing was om die moontlike voorkoms van verskille in geheuefunksie in huidige gebruikers van metamfetamien, rehabiliterende gebruikers, sowel as ‘n kontrolegroep van dwelmmiddel-naïewe demografies-passende individue te bepaal. Uitvoerende funksie is gemeet met ‘n neurokognitiewe toetsbattery wat die geheuefunksies van 14 huidige gebruikers van metamfetamien, 17 rehabiliterende metamfetamienverslaafde individue en 18 dwelmmiddel-naïewe deelnemers, gepas in terme van ouderdom, geslag en opvoedkundige status, bepaal het. Die resultate dui aan dat dat die rehabiliterende metamfetamiengebruikers die grootste geheueuitvalle getoon het in vergelyking met sowel die huidige gebruikers as die kontrolegroep. Die huidige metamfetamiengebruikers het ook matige geheueuitvalle getoon, spesifiek in visuele leer en retensie. Dit is moontlik dat die geheueuitvalle wat deur metamfetamiengebruikers ervaar word, verband hou met strukturele en funksionele verandering in die breingebiede wat met geheue geassosieer word, as gevolg van metamfetamienvergiftiging. Die swak prestasie van die rehabiliterende metamfetamienverslaafde persone in vergelyking met die huidige gebruikers word verduidelik in terme van die naasmekaarstelling van die stimulerende en aanvullende effek van metamfetamien soos ervaar deur die huidige gebruikers versus die neurotransmitteruitputting en strukturele breinveranderinge in die rehabiliterende individue. Die kontrolegroep het ‘n beter resultaat getoon omdat hulle geen neurotoksiese effekte van metamfetamien gehad het nie. 

Drug-related cues exacerbate decision making and increase craving in heroin addicts at different abstinence times

RATIONALE

Relapse is a persistent problem in the management of addiction. Drug-related cues are powerful instigators of relapse. Impulsive decision making may contribute to relapse through a poorly considered assessment of the consequences of drug use. Drug cues robustly increase subjective craving, which is frequently associated with relapse.

OBJECTIVE

The present study explored the effects of drug-related cues on decision making and craving in heroin addicts at different abstinence times: 1, 3, 12, and 24 months.

METHODS

The 75 male participants were given 5 min exposure to neutral and drug-associated cues while decision making performance, craving, blood pressure, heart rate, and emotional state pre- and post-exposure were assessed. The Iowa Gambling Task was used to evaluate decision making ability in heroin addicts.

RESULTS

Drug-related cues exacerbated impulsive decision making and increased craving, heart rate, and systolic pressure in heroin addicts at all abstinence times.

CONCLUSIONS

Drug-related cues aggravated decision making and increased craving in former heroin addicts who had been drug-free for 1-24 months, which might have significant clinical implications for the prevention of relapse.

Orbitofrontal volumes in early adolescence predict initiation of cannabis use: a 4-year longitudinal and prospective study

BACKGROUND

There is growing evidence that long-term, heavy cannabis use is associated with alterations in regional brain volumes. Although these changes are frequently attributed to the neurotoxic effects of cannabis, it is possible that some abnormalities might predate use and represent markers of vulnerability. To date, no studies have examined whether structural brain abnormalities are present before the onset of cannabis use. This study aims to determine whether adolescents who have initiated cannabis use early (i.e., before age 17 years) show premorbid structural abnormalities in the amygdala, hippocampus, orbitofrontal cortex, and anterior cingulate cortex.

METHODS

Participants (n = 121) were recruited from primary schools in Melbourne, Australia, as part of a larger study examining adolescent emotional development. Participants underwent structural magnetic resonance imaging at age 12 years and were assessed for cannabis use 4 years later, at age 16 years. At the follow-up assessment, 28 participants had commenced using cannabis (16 female subjects [57%]), and 93 had not (43 female subjects [46%]).

RESULTS

Smaller orbitofrontal cortex volumes at age 12 years predicted initiation of cannabis use by age 16 years. The volumes of other regions (amygdala, hippocampus, and anterior cingulate cortex) did not predict later cannabis use.

CONCLUSIONS

These findings suggest that structural abnormalities in the orbitofrontal cortex might contribute to risk for cannabis exposure. Although the results have important implications for understanding neurobiological predictors of cannabis use, further research is needed to understand their relationship with heavier patterns of use in adulthood as well as later abuse of other substances.

An fMRI investigation of cerebellar function during verbal working memory in methadone maintenance patients

Working memory is impaired in opioid-dependent individuals, yet the neural underpinnings of working memory in this population are largely unknown. Previous studies in healthy adults have demonstrated that working memory is supported by a network of brain regions that includes a cerebro-cerebellar circuit. The cerebellum, in particular, may be important for inner speech mechanisms that assist verbal working memory. This study used functional magnetic resonance imaging to examine brain activity associated with working memory in five opioid-dependent, methadone-maintained patients and five matched, healthy controls. An item recognition task was administered in two conditions: (1) a low working memory load "match" condition in which participants determined whether target letters presented at the beginning of the trial matched a probe item, and (2) a high working memory load "manipulation" condition in which participants counted two alphabetical letters forward of each of the targets and determined whether either of these new items matched a probe item. Response times and accuracy scores were not significantly different between the groups. FMRI analyses indicated that, in association with higher working memory load ("manipulation" condition), the patient group exhibited hyperactivity in the superior and inferior cerebellum and amygdala relative to that of controls. At a more liberal statistical threshold, patients exhibited hypoactivity in the left prefrontal and medial frontal/pre-SMA regions. These results indicate that verbal working memory in opioid-dependent individuals involves a disrupted cerebro-cerebellar circuit and shed light on the neuroanatomical basis of working memory impairments in this population.

Diffusion tensor imaging of white matter networks in individuals with current and remitted alcohol use disorders and comorbid conditions

Individuals with alcohol use disorders show white matter abnormality relative to normal samples, but differences in white matter profiles have not yet been investigated as a function of abstinence. Individuals with current alcohol use disorders (AUD-C; n = 10), individuals with alcohol use disorders in remission for at least 1 year (AUD-R; n = 9), and healthy control participants (HC; n = 15) matched to alcohol groups on age and smoking status underwent MRI. Diffusion tensor imaging (DTI) data were analyzed using tract-based spatial statistics (TBSS). Compared with HC, AUD-C showed reduced axial diffusivity in bilateral frontal and temporal white matter. In AUD-R, lower fractional anisotropy relative to HC was widespread in bilateral parietal regions. A combined AUD-C and AUD-R group had decreased fractional anisotropy primarily in the fornix and thalamus. In conclusion, AUD-R manifested damage in parietal regions integral to processing of visuospatial information and self-awareness whereas AUD-C showed abnormal diffusivity in fronto-temporal regions that regulate impulsivity, attention, and memory. As a combined group, AUD individuals exhibited abnormality in subcortical areas associated with sensory processing and memory. White matter differences in individuals with AUD may be attributable to premorbid vulnerability or persisting effects of alcohol abuse, but the pattern of abnormality across groups suggests that these abnormalities may be secondary to alcohol use.

The neurobiology of cognitive control in successful cocaine abstinence

INTRODUCTION

Extensive evidence demonstrates that current cocaine abusers show hypoactivity in anterior cingulate and dorsolateral prefrontal cortex and respond poorly relative to drug-naïve controls on tests of executive function. Relatively little is known about the cognitive sequelae of long-term abstinence in cocaine addicts.

METHODS

Here, we use a GO-NOGO task in which successful performance necessitated withholding a prepotent response to assay cognitive control in short- and long-term abstinent cocaine users (1-5 weeks and 40-102 weeks, respectively).

RESULTS

We report significantly greater activity in prefrontal, cingulate, cerebellar and inferior frontal gyrii in abstinent cocaine users for both successful response inhibitions and errors of commission. Moreover, this relative hyperactivity was present in both abstinent groups, which, in the presence of comparable behavioral performance, suggests a functional compensation.

CONCLUSIONS

Differences between the short- and long-abstinence groups in the patterns of functional recruitment suggest different cognitive control demands at different stages in abstinence. Short-term abstinence showed increased inhibition-related dorsolateral and inferior frontal activity indicative of the need for increased inhibitory control while long-term abstinence showed increased error-related ACC activity indicative of heightened behavioral monitoring. The results suggest that the integrity of prefrontal systems that underlie cognitive control functions may be an important characteristic of successful long-term abstinence.

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

RATIONALE

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

OBJECTIVES AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Adolescent brain development and underage drinking in the United States: identifying risks of alcohol use in college populations

Alcohol use typically is initiated during adolescence, a period that coincides with critical structural and functional maturation of the brain. Brain maturation and associated improvements in decision making continue into the third decade of life, reaching a plateau within the period referred to as emerging adulthood (18-24 years). This particular period covers that of traditionally aged college students, and includes the age (21 years) when alcohol consumption becomes legal in the United States. This review highlights neurobiological evidence indicating the vulnerabilities of the emerging-adult brain to the effects of alcohol. Factors increasing the risks associated with underage alcohol use include the age group's reduced sensitivity to alcohol sedation and increased sensitivity to alcohol-related disruptions in memory. On the individual level, factors increasing those risks are a positive family history of alcoholism, which has a demonstrated effect on brain structure and function, and emerging comorbid psychiatric conditions. These vulnerabilities-of the age group, in general, as well as of particular individuals-likely contribute to excessive and unsupervised drinking in college students. Discouraging alcohol consumption until neurobiological adulthood is reached is important for minimizing alcohol-related disruptions in brain development and decision-making capacity, and for reducing the negative behavioral consequences associated with underage alcohol use.

Immediate survival focus: synthesizing life history theory and dual process models to explain substance use

Researchers have recently applied evolutionary life history theory to the understanding of behaviors often conceived of as prosocial or antisocial. In addition, researchers have applied cognitive science to the understanding of substance use and used dual process models, where explicit cognitive processes are modeled as relatively distinct from implicit cognitive processes, to explain and predict substance use behaviors. In this paper we synthesized these two theoretical perspectives to produce an adaptive and cognitive framework for explaining substance use. We contend that this framework provides new insights into the nature of substance use that may be valuable for both clinicians and researchers.

Relationship between measures of inhibitory processes in patients with schizophrenia: role of substance abuse disorders

Disruption of prepulse inhibition of the startle response (PPI) has been widely identified in patients with schizophrenia, as well as impairment in many domains of cognitive functioning. However, there is some controversy regarding the relationship between PPI and the different neuropsychological tasks assessing inhibition. This controversy may be due to the influence of other variables, such as substance abuse. We aimed to determine whether differences in inhibition in schizophrenia subjects were related to their pattern of substance use and whether there was a correlation between the changes in each process. PPI and neuropsychological functioning were studied in three groups of subjects with schizophrenia (N=73): tobacco dependents (ToD; n=22), multiple substance abusers (MSUD; n=31) and non-substance abusers (non-SUD; n=20). All subjects were assessed using PPI and neuropsychological tests (Stroop and Wisconsin Card Sorting Test [WCST]). ToD showed better pre-attentive inhibitory function compared to the other two groups, and MSUD showed lower resistance to interference. Furthermore, significant correlations were found between PPI, Stroop, and WCST. Our data suggest that there is a relationship between the different tasks assessing inhibition in schizophrenia, being affected by substance abuse history. We also found differences in inhibition capacity depending on substance abuse in patients with schizophrenia.

Novel object recognition memory: measurement issues and effects of MDMA self-administration following short inter-trial intervals

The present study was undertaken to examine effects of self-administered MDMA on novel object exploration (NOR) memory. Self-administration was conducted during daily 2 h tests that continued until a total of 165 mg/kg was self-administered (range = 13-41 days for individual rats). Control rats were placed in the self-administration boxes during daily sessions but did not receive any drug. One or 10 weeks following the last self-administration session, memory was assessed using a standard NOR task. When exploration time was used as the dependent measure for the control rats, there was no consistent pattern of change as a function of inter-trial interval (ITI) and exploration times failed to reveal decay in the function relating exploration to ITI. When number of approaches was examined as a function of ITI, however, there was a preference for the novel object following the short ITIs (1-15 min) and the function relating preference to ITI decayed with longer ITIs. When tested 7 days following the last self-administration session, rats that self-administered MDMA failed to demonstrate NOR even following the shortest ITI of 1 min. The data support the idea that MDMA self-administration produces cognitive deficits and are consistent with the idea that attentional processes become disrupted. There was, however, recovery of NOR memory when rats were tested following an extended drug-free period of 70 days. Thus, the deficits are transient and recovery was apparent.

Verbal learning and memory in adolescent cannabis users, alcohol users and non-users

RATIONALE

Long-term heavy cannabis use can result in memory impairment. Adolescent users may be especially vulnerable to the adverse neurocognitive effects of cannabis.

OBJECTIVES AND METHODS

In a cross-sectional and prospective neuropsychological study of 181 adolescents aged 16-20 (mean 18.3 years), we compared performance indices from one of the most widely used measures of learning and memory--the Rey Auditory Verbal Learning Test--between cannabis users (n=52; mean 2.4 years of use, 14 days/month, median abstinence 20.3 h), alcohol users (n=67) and non-user controls (n=62) matched for age, education and premorbid intellectual ability (assessed prospectively), and alcohol consumption for cannabis and alcohol users.

RESULTS

Cannabis users performed significantly worse than alcohol users and non-users on all performance indices. They recalled significantly fewer words overall (p<0.001), demonstrating impaired learning (p<0.001), retention (p<0.001) and retrieval (p<0.05) (Cohen's d 0.43-0.84). The degree of impairment was associated with the duration, quantity, frequency and age of onset of cannabis use, but was unrelated to alcohol exposure or other drug use. No gender effects were detected and the findings remained after controlling for premorbid intellectual ability. An earlier age of onset of regular cannabis use was associated with worse memory performance after controlling for extent of exposure to cannabis.

CONCLUSIONS

Despite relatively brief exposure, adolescent cannabis users relative to their age-matched counterparts demonstrated similar memory deficits to those reported in adult long-term heavy users. The results indicate that cannabis adversely affects the developing brain and reinforce concerns regarding the impact of early exposure.

Glutamatergic hyperfunctioning during alcohol withdrawal syndrome: therapeutic perspective with zinc and magnesium

It is known that the glutamatergic pathways are hyperfunctioning during alcohol withdrawal syndrome. It has been demonstrated that hyperfunctioning of this system causes a great damage to the superior cortical activity, the ability to concentrate and the control of impulses. Recent studies show that the cations zinc and magnesium modulate the glutamatergic function, reducing it to non-toxic levels, yet not reducing it to the point of depriving this neurotransmitter of its normal activity. New perspectives of treatment focus on the modulation of this system, having, as a result, reestablishment of impulse control abilities, damage prevention to the hippocampus and the amygdala and prevention of future relapses.

Evidence for subtle verbal fluency deficits in occasional stimulant users: quick to play loose with verbal rules

Psychostimulants like cocaine and amphetamine are commonly abused by young adults who often state that they take these drugs to increase social or cognitive performance. The current study tested the hypothesis that individuals at early stages of occasional stimulant use show subtle executive dysfunctions such as verbal fluency deficits. 155 young (age 18-25), non-dependent occasional users of stimulants and 49 stimulant naïve comparison subjects performed the Delis-Kaplan Verbal Fluency test. Correlation and median split analyses were conducted to account for stimulant history and co-drug use. Compared to stimulant naïve subjects, occasional stimulant users generated significantly more responses on an over-learned verbal fluency task (Category Fluency), but at the expense of increased error rates (Set Loss and Repetition Errors). These performance differences were not related to lifetime uses of stimulants or marijuana. Taken together, these results support the hypothesis that individuals who are using stimulants occasionally exhibit subtle executive dysfunctions when required to generate verbal sets under time pressure. In particular, occasional stimulant users apply quickly but inaccurately verbal rules, which may represent a mix of diminished cognitive flexibility along with increased rigidity and impulsivity. This specific executive dysfunction may help to identify individuals at risk for stimulant use or dependence.

Stimulant abuse: pharmacology, cocaine, methamphetamine, treatment, attempts at pharmacotherapy

The high prevalence of stimulant abuse and its harmful consequences make the screening, diagnosis, and referral for treatment of persons with stimulant abuse a top concern for primary care providers. Having a working knowledge of use patterns, clinical symptomatology, end-organ effects, and advances in treatment of stimulant abuse is essential. Although cocaine and amphetamine have different use patterns, duration of action, and so forth, the consequences of use are remarkably similar. Primary care is at the forefront of screening, brief risk reduction interventions, and diagnosis of medical sequelae, with referral to addiction specialist treatment when necessary.

Nondependent stimulant users of cocaine and prescription amphetamines show verbal learning and memory deficits

BACKGROUND

Stimulants are used increasingly to enhance social (cocaine) or cognitive performance (stimulants normally prescribed, prescription stimulants [e.g., methylphenidate, amphetamines]). Chronic use, by contrast, has been associated with significant verbal memory and learning deficits. This study sought to determine whether subtle learning and memory problems characterize individuals who exhibit occasional but not chronic use of stimulants.

METHODS

One hundred fifty-four young (age 18-25), occasional, nondependent stimulant users and 48 stimulant-naive comparison subjects performed the California Verbal Learning Test II. Lifetime uses of stimulants and co-use of marijuana were considered in correlation and median split analyses.

RESULTS

Compared with stimulant-naive subjects, occasional stimulant users showed significant performance deficits, most pronounced in the verbal recall and recognition domains. Lifetime uses of stimulants and marijuana did not affect California Verbal Learning Test II performance. The type of stimulant used, however, was of major relevance: users of cocaine only were less impaired, whereas cumulative use of prescription stimulants was associated with impaired verbal learning and memory capacities.

CONCLUSIONS

These results support the hypothesis of subtle and possibly pre-existing neurocognitive deficiencies in occasional users of stimulants, which might be related to the motivation for using these drugs. More importantly, despite beneficial short-term effects, cumulative use, particularly of prescription amphetamines and methylphenidate, intensifies these deficits.

Anormalidades cognitivas no uso da cannabis

OBJETIVO: Evidências de que o uso de cannabis prejudica funções cognitivas em humanos têm-se acumulado nas décadas recentes. O propósito desta revisão é o de atualizar o conhecimento nesta área com novos achados a partir da literatura mais recente. MÉTODO: As buscas na literatura foram realizadas utilizando-se o banco de dados Web of Science até fevereiro de 2010. Foram buscados os termos "cannabi*" ou "marijuana" e "cogniti*" ou "memory" ou "attention" ou "executive function", e os estudos em humanos foram revisados preferencialmente em relação aos estudos em animais. DISCUSSÃO: O uso de cannabis prejudica a memória, a atenção, o controle inibitório, as funções executivas e a tomada de decisões, tanto durante como após o período de intoxicação aguda, persistindo por horas, dias, semanas ou mais após o último uso. Os estudos de desafio farmacológico em humanos estão elucidando a natureza e os substratos neurais das alterações cognitivas associadas a vários canabinoides. O uso pesado ou de longo prazo de cannabis parece resultar em anormalidades cognitivas mais duradouras e possivelmente em alterações cerebrais estruturais. Efeitos cognitivos adversos maiores estão associados ao uso de cannabis quando este começa no início da adolescência. CONCLUSÃO: O sistema canabinoide endógeno está envolvido nos mecanismos de regulação neural que modulam os processos subjacentes a uma gama de funções cognitivas que estão prejudicadas pela cannabis. Os déficits em usuários humanos muito provavelmente refletem, portanto, neuroadaptações e o funcionamento alterado do sistema canabinoide endógeno.

Executive function in schizophrenia: influence of substance use disorder history

Cognitive function in schizophrenia has been associated with different sociodemographic and clinical variables. Substance use disorder (SUD) history has also been associated with cognition in schizophrenia; however, contradictory results have been found regarding its influence on cognitive function. Our aim was to study the relationship between executive function and a) age, b) duration of illness, c) number of psychotic episodes, d) positive symptoms, and e) negative symptoms, in a sample of schizophrenic patients, and secondly to study whether these relationships persisted after stratification of the sample according to the presence or absence of SUD history. A final sample of 203 schizophrenic patients were evaluated for psychotic symptoms using the PANSS, and assessed using a neuropsychological battery to calculate a composite executive function score. Linear regression analyses were performed, with this executive score as the dependent variable, and age, duration of illness, number of psychotic episodes, positive PANSS score and negative PANSS score as independent variables. For the total sample, the regression model showed three variables to be significant predictors of the executive score: age (p=0.004), number of episodes (p=0.027), and PANSS negative score (p=0.003). However, once the sample was stratified, the regression model showed age (p=0.011) and number of episodes (p=0.011) to be predictor variables for the executive score in the group of schizophrenic patients with SUD history, while age (p=0.028) and PANSS negative score (p=0.006) were predictors in the group of schizophrenic patients without such history. These findings highlight the importance of considering SUD history in studies of cognitive function in schizophrenia.

Increased activation of the ACC during a spatial working memory task in alcohol-dependence versus heavy social drinking

BACKGROUND

Activation of the anterior cingulate cortex (ACC) in a spatial working memory task has been associated with risk factors for alcohol use disorders such as low alcohol effects and positive alcohol expectations in adolescents. To transfer these results into adults, we used the same task in adults.

METHODS

During functional magnetic resonance imaging, 12 light social, 7 heavy social, and 11 non-abstinent-dependent alcohol drinkers performed a spatial working memory task and completed measures of automatic alcohol-related thoughts and behavior (Obsessive-Compulsive Drinking Scale-OCDS), alcohol use of the last 90 days, and general intelligence.

RESULTS

Behavioral performance in the spatial working memory task was not significantly different in all 3 groups. Controlling for differences in general intelligence alcohol-dependent participants showed a higher task-related activation of the dorsal ACC (dACC) in comparison with light and heavy social drinkers. Measures of the OCDS were positively correlated with the activation in the left hippocampus and right thalamus in all participants.

CONCLUSIONS

Our results support the findings of increased dACC activation during a spatial working memory task as a risk factor for alcohol dependence. Increased task-related activation in the dACC was only observed in alcohol-dependent participants and not in heavy social drinkers with comparable alcohol consumption. Furthermore, the absence of behavioral performance differences between groups as well as an association between dACC activation and working memory performance indicates subtle working memory deficits. Low capacity of working memory has been linked to more automatic and less self-regulated behavior in studies on natural reward processing. Therefore, additional neural activation during performance of the non-alcohol-related working memory task in participants with higher OCDS values in the left hippocampus and the right thalamus may be a consequence of decreased neural capacity because of distracting alcohol-related thoughts.

The role of executive control in human drug addiction

Recent neurobiological models propose that executive control deficits play a critical role in the development and maintenance of drug addiction. In this review, we discuss recent advances in our understanding of executive control processes and their constituent neural network, and examine neuropsychological and neuroimaging evidence of executive control dysfunction in addicted drug users. We explore the link between attentional biases to drug-related stimuli and treatment outcome, and discuss recent work demonstrating that the hedonic balance between drug cues and natural reinforcers is abnormal in addiction. Finally, we consider the potential impact of early drug use on the developing adolescent brain, and discuss research examining premorbid executive control impairments in drug-naïve "at-risk" populations.

Polymorphisms in the 3' UTR of the serotonin transporter are associated with cognitive flexibility in rhesus macaques

The serotonin system is an important neurophysiological mediator of many behavioral phenotypes. Genetic variation within this system is thought to contribute not only to the natural range of behavioral differences, but also to neuropsychiatric pathologies. Cognitive flexibility, the ability to change patterns of response as reward context shifts, is an important trait that underlies many complex social interactions. Environmental manipulations of the serotonin system have been shown to alter performance on tests measuring cognitive flexibility. Variation at the serotonin transporter promoter region (5HTTLPR) has recently been shown to associate with the performance of rhesus monkeys on an object discrimination reversal learning task [Izquierdo et al., 2007]. Here, we demonstrate that functional genetic variation at the serotonin transporter 3' untranslated region, independent of 5HTTLPR, also associates with performance in an object discrimination reversal learning task in rhesus macaques. The polymorphisms comprising the T:G:T haplotype (T1970, G1991, and T2327) were associated with fewer errors on a reversal learning test and greater levels of cognitive flexibility. We have previously demonstrated that the T:G:T haplotype renders lower levels of gene expression in vitro, paralleling the functionality of human 3' UTR haplotypes, as well as the short allele of 5HTTLPR found in both macaques and humans. The 3' UTR haplotypes are independent and in linkage equilibrium with the 5HTTLPR locus. Together, these data lead to the intriguing possibility that differences observed in human cognitive flexibility, whether naturally or in pathological states, may be associated with genetic variation in the serotonin transporter 3' untranslated region also.

Treating drug abuse and addiction in the criminal justice system: improving public health and safety

Despite increasing evidence that addiction is a treatable disease of the brain, most individuals do not receive treatment. Involvement in the criminal justice system often results from illegal drug-seeking behavior and participation in illegal activities that reflect, in part, disrupted behavior ensuing from brain changes triggered by repeated drug use. Treating drug-involved offenders provides a unique opportunity to decrease substance abuse and reduce associated criminal behavior. Emerging neuroscience has the potential to transform traditional sanction-oriented public safety approaches by providing new therapeutic strategies against addiction that could be used in the criminal justice system. We summarize relevant neuroscientific findings and evidence-based principles of addiction treatment that, if implemented in the criminal justice system, could help improve public heath and reduce criminal behavior.

HCV treatment decision-making substance use experiences and hepatitis C treatment decision-making among HIV/HCV Coinfected Adults

Hepatitis C virus (HCV) infection is a major source of morbidity and mortality among substance users and persons living with human immunodeficiency virus (HIV) infection. Treatment for chronic HCV infection involves complex decision-making. These decisions are even more complicated in persons with HIV and substance use related problems. A secondary analyses of qualitative data collected in the United States (2004-2005) with 31 HIV/HCV coinfected adults (48% women; mean age 44.7 years) revealed three themes related to substance use (substance use evolution, revolving door: going back out and reconstructing life) and two HCV treatment decision-making themes (HCV infection treatment issues: not a priority, fear, misinformation and get clean and try it). Study limitations and implications are discussed.