Consommation de substances psychoactives, problèmes affectifs et traits de personnalité : test de deux modèles d’association

Value-based decision-making network functional connectivity correlates with substance use and delay discounting behaviour among young adults

Substance use disorders are characterized by reduced control over the quantity and frequency of psychoactive substance use and impairments in social and occupational functioning. They are associated with poor treatment compliance and high rates of relapse. Identification of neural susceptibility biomarkers that index risk for developing a substance use disorder can facilitate earlier identification and treatment. Here, we aimed to identify the neurobiological correlates of substance use frequency and severity amongst a sample of 1,200 (652 females) participants aged 22-37 years from the Human Connectome Project. Substance use behaviour across eight classes (alcohol, tobacco, marijuana, sedatives, hallucinogens, cocaine, stimulants, opiates) was measured using the Semi-Structured Assessment for the Genetics of Alcoholism. We explored the latent organization of substance use behaviour using a combination of exploratory structural equation modelling, latent class analysis, and factor mixture modelling to reveal a unidimensional continuum of substance use behaviour. Participants could be rank ordered along a unitary severity spectrum encompassing frequency of use of all eight substance classes, with factor score estimates generated to represent each participant's substance use severity. Factor score estimates and delay discounting scores were compared with functional connectivity in 650 participants with imaging data using the Network-based Statistic. This neuroimaging cohort excludes participants aged 31 and over. We identified brain regions and connections correlated with impulsive decision-making and poly-substance use, with the medial orbitofrontal, lateral prefrontal and posterior parietal cortices emerging as key hubs. Functional connectivity of these networks could serve as susceptibility biomarkers for substance use disorders, informing earlier identification and treatment.

Initiation of drug and alcohol use and personality development during adolescence

Personality traits predict both the initiation and continued usage of alcohol and drugs. Less established is if substance use is associated with subsequent changes in personality, especially during the sensitive period of adolescence. We used three approaches to disentangle selection and socialization effects to address whether substance use is associated with personality development (impulsivity, sensation-seeking, depression, self-esteem). First, we used a multi-wave longitudinal sample of adolescents ( N = 8,303) from the National Longitudinal Survey of Youth - Child and Young Adult dataset to study the first use of several substances. Second, we used propensity score weighting to equate users and abstainers on a range of background variables. Third, we investigated changes before, during, and after initiation of substances. Overall, there was unique variability and effects in personality across time for average levels, trajectories, and magnitudes of change both between users and abstainers as well as within users of specific substances. Results suggest that initiation of substance use is associated with changes in personality; the specifics of which are largely contingent upon the substance being used. Impulsivity and sensation-seeking were the traits associated with the most change while cocaine and cigarettes were the substances associated with the greatest changes.

[E-cigarette use among cannabis users and multi-users of psychoactive products: A cohort study]

INTRODUCTION

There is no evidence in the literature relating to the evolution of e-cigarette use among cannabis users and multi-users (of alcohol, tobacco or cannabis).

OBJECTIVE

To describe the evolution over 12 months of e-cigarette use in cannabis users and multi-users.

METHODS

A prospective observational cohort study in general practice, between 2015 and 2016.

RESULTS

A total of 4.8% of monitored cannabis users remained or became current users of e-cigarettes by the end of the monitoring period versus 4.5% among non-users of cannabis, with no statistically significant difference. A total of 5.1% of monitored multi-users remained or became current users of e-cigarettes by the end of the monitoring period versus 2.4% among the non-multi-users, with no statistically significant difference. Cannabis users and multi-users reported more e-cigarette experimentation through curiosity and following someone's suggestion, compared to non-cannabis users or non multi-users. No statistically significant association was found between cannabis or multi-drug use and staying or becoming a current e-cigarette user over 12 months.

CONCLUSION

Cannabis users and multi-users would tend to experiment with e-cigarettes more than other patients but this use would not be sustained.

[Problematic Internet use, time spent online and personality traits]

BACKGROUND

Internet addiction or problematic Internet use is a recent and increasingly recognized disorder which has been consistently associated with many psychiatric disorders, adding to the documented negative consequences of problematic Internet use. However, very few studies have examined the relationship between problematic Internet use and personality traits and none in a French sample. Moreover, those which have evaluated this relationship have mainly been conducted on small samples.

OBJECTIVE

The main goal of our study was to explore the relationship between problematic Internet use, time spent online and personality traits in a French sample, taking into account the presence of depressive symptoms, and gender.

METHODS

A sample of 276 participants aged from 18 to 50 (M=28; SD=8.9) completed a questionnaire assessing problematic Internet use, time spent online, the presence of ten personality traits and depressive symptoms.

RESULTS

Our results revealed significant differences between genders. Among men, problematic Internet use was associated with personality clusters A and B while in women no cluster or personality traits were associated. Time spent online was predicted by schizoid personality traits among men and avoidant personality traits among women.

DISCUSSION

Our results indicate that cluster A (schizoid and schizotypal) and cluster B traits (borderline and antisocial) play a more important role in problematic Internet use than cluster C traits among men. Differences between men and women regarding the relationships between personality traits, time online and problematic Internet use may be related to differences in the activities engaged in by men and women online. We observed that communication websites use was more prevalent among women while erotic, gambling and shopping websites use was more prevalent among men suggesting that the characteristics of problematic Internet use may vary according to gender.

CONCLUSION

Few studies have examined the relationship between problematic Internet use, time spent online and personality traits, and none among a French sample. These results suggest the importance of assessing the impact of personality traits on Internet use, particularly on time spent online, by differentiating results in terms of gender and online activities.

Prevalence of Substance Abuse Among Dormitory Students of Shahid Beheshti University of Medical Sciences, Tehran, Iran

BACKGROUND

Adolescence is a risky period with high tendency towards drug abuse. Addressing the problem of drug abuse among students is essential.

OBJECTIVES

This study was carried out in 2013 with the purpose of investigating the prevalence of substance abuse among dormitory students of Shahid Beheshti University of Medical Sciences.

PATIENTS AND METHODS

In this descriptive analytical study, which was carried out in 2013, a total of 604 students living at dormitories of Shahid Beheshti University of Medical Sciences were selected by random sampling method. A questionnaire designed by the researcher was used to collect the data. Data were analyzed using descriptive statistics and chi-square test.

RESULTS

The prevalence of substance abuse among the students was 15.4%. With respect to the types of the drug used by students, the highest frequencies belonged to smoking 4.47% and hookah with 42.9%. Forty-eight percent of the students, who used drugs, started it for the first time when they were 18 years old or younger. About 58% of students used drugs for the first time in dormitories and parks. Students' meetings and parties with friends were frequent occasions for substance abuse (47.5%).

CONCLUSIONS

Students are considered one of the most vulnerable groups of society. The students living in dormitories are more vulnerable to drug abuse due to the lack of parental supervision and the impact of peer pressure. Therefore, localization of acceptance at Universities in order to prevent cultural mixing of students and education programs for teaching life skills to students efficiently reduce their substance abuse.

Convergent pharmacological mechanisms in impulsivity and addiction: insights from rodent models

Research over the last two decades has widely demonstrated that impulsivity, in its various forms, is antecedent to the development of drug addiction and an important behavioural trait underlying the inability of addicts to refrain from continued drug use. Impulsivity describes a variety of rapidly and prematurely expressed behaviours that span several domains from impaired response inhibition to an intolerance of delayed rewards, and is a core symptom of attention deficit hyperactivity disorder (ADHD) and other brain disorders. Various theories have been advanced to explain how impulsivity interacts with addiction both causally and as a consequence of chronic drug abuse; these acknowledge the strong overlaps in neural circuitry and mechanisms between impulsivity and addiction and the seemingly paradoxical treatment of ADHD with stimulant drugs with high abuse potential. Recent years have witnessed unprecedented progress in the elucidation of pharmacological mechanisms underpinning impulsivity. Collectively, this work has significantly improved the prospect for new therapies in ADHD as well as our understanding of the neural mechanisms underlying the shift from recreational drug use to addiction. In this review, we consider the extent to which pharmacological interventions that target impulsive behaviour are also effective in animal models of addiction. We highlight several promising examples of convergence based on empirical findings in rodent-based studies.

The role of impulsivity in dropout from treatment for cigarette smoking

Impulsivity is a variable that has been associated with drug use. This study analyzes impulsivity from two different paradigms, one considering it as a trait and the other based on its behavioral correlates, such as disinhibition and impulsive decision-making in the treatment prognosis (maintain abstinence, relapse and dropout) of smokers after outpatient treatment. The participants in the study were 113 smokers who requested treatment for nicotine addiction. They were assigned to three groups according to whether or not they remained abstinent one month after beginning treatment; thus, group 1 was abstinent, group 2 had relapsed, and group 3 had dropped out of treatment. The participants filled out the Semi-structured Interview for Smokers, the Fargerström Test for Nicotine Dependence, the Temperament and Character Inventory-Revised (TCI-R) and the Delay Discounting Task (DDT). The Delay Discounting variable presents lower scores in the dropout group than in the relapse and abstinent groups, with the highest scores in the relapse group. Differences were also found on the Harm Avoidance (HA) variable, with lower scores in the dropout group compared to the relapse group. The importance of these results lies in the consideration of the smoker's personality profile in order to prevent both dropout and relapse.

Risk perception, motives and behaviours in university students

Risky behaviours among young people are relatively frequent, with several motives and attitudes lying behind. Our objective was to evaluate the role of risk perception, attractiveness and motives for risk behaviour taking among university students in Lebanon. A cross-sectional study was carried out using a proportionate cluster sample of Lebanese students in public and private universities. Items of risk intake and perception scale, attractiveness of risky behaviours, and motives for risky behaviours were assessed, in addition to cigarette and waterpipe smoking and dependence, alcohol problematic consumption and mental distress scale. After verifying the validity of scales and reliability in the university students' population, we found that risk perception was associated with lower risk intake, while risk attractiveness was a driver for it. Moreover, motives differed in their driving of risky behaviour, a particular point was that women indicated more goal achievement objectives, the latter concept was associated with lower risk taking. University students in Lebanon, women in particular, demonstrated wiser behaviour and may benefit from heath education programme to increase their awareness about risky behaviours. Identifying other personal, environmental, social and psychological predictors may also be important to improve effectiveness of these programmes.

Behavioral addictions in euthymic patients with bipolar I disorder: a comparison to controls

BACKGROUND

Bipolar disorder may be associated with a hypersensitive behavioral approach system and therefore to increased reward sensitivity. The objective of this study is to explore the interrelationships between bipolar disorder, behavioral addictions, and personality/temperament traits in a group of euthymic outpatients with bipolar I disorder and in a group of comparison subjects.

METHODS

Fifty clinically stable patients and 50 comparison subjects matched for age, sex, and educational level were administered the Temperament and Character Inventory-140 and the Behavioral Addiction Scale.

RESULTS

The patient group scored significantly higher than comparison subjects for two benign behavioral addictions (music, shopping) as well as for smoking. Comparison subjects scored higher on two harmful behavioral addictions (drugs, alcohol). Novelty Seeking was positively correlated with harmful addictions, and Cooperativeness was negatively correlated with harmful addictions, in both groups.

DISCUSSION

The hypersensitive behavioral approach system model of bipolar disorder would predict higher levels of various addictions in bipolar patients as compared to controls. In this study, this was true for three behavioral addictions, whereas controls showed higher levels of behavioral addiction to drugs and alcohol. This may be because the patients in this study are stable, have received considerable psychoeducation, and are relatively adherent to their medication recommendations. Temperament and character traits may play roles both as risk and protective factors regarding behavioral addictions.

The detrimental effects of emotional process dysregulation on decision-making in substance dependence

Substance dependence is complex and multifactorial, with many distinct pathways involved in both the development and subsequent maintenance of addictive behaviors. Various cognitive mechanisms have been implicated, including impulsivity, compulsivity, and impaired decision-making. These mechanisms are modulated by emotional processes, resulting in increased likelihood of initial drug use, sustained substance dependence, and increased relapse during periods of abstinence. Emotional traits, such as sensation-seeking, are risk factors for substance use, and chronic drug use can result in further emotional dysregulation via effects on reward, motivation, and stress systems. We will explore theories of hyper and hypo sensitivity of the brain reward systems that may underpin motivational abnormalities and anhedonia. Disturbances in these systems contribute to the biasing of emotional processing toward cues related to drug use at the expense of natural rewards, which serves to maintain addictive behavior, via enhanced drug craving. We will additionally focus on the sensitization of the brain stress systems that result in negative affect states that continue into protracted abstinence that is may lead to compulsive drug-taking. We will explore how these emotional dysregulations impact upon decision-making controlled by goal-directed and habitual action selections systems, and, in combination with a failure of prefrontal inhibitory control, mediate maladaptive decision-making observed in substance dependent individuals such that they continue drug use in spite of negative consequences. An understanding of the emotional impacts on cognition in substance dependent individuals may guide the development of more effective therapeutic interventions.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Biographical data of patients in drug substitution programmes

BACKGROUND

We investigated drug substitution patients' biographical data for counselling, to recognize social and other risk factors and additionally consumed drugs.

METHODS

We decided on a retrospective, descriptive investigation in one practice. A preformed pattern of questions was applied to the charts of drug-substituted patients.

RESULTS

We found data on 332 men and 114 women. Statistical connections were counted by SPSS 11.5 and Chi-square-tests. Two-thirds had completed compulsory school, one third had some kind of vocational training, and current occupation was frequently different to training. 72% of the patients claimed to have "a supportive family relationship with their families". 25% were in touch with their children. Drug abuse started early, below the age of 14 for nearly 25% of our group.179 patients had withdrawal treatment.138 patients (31%) confirmed hepatitis C infection, 23 out of 441 had tested HIV positive (5.2%).

CONCLUSIONS

Inconstant relationships to family, education and profession combine to early drug use.

Applications of positron emission tomography in animal models of neurological and neuropsychiatric disorders

Positron emission tomography (PET) provides dynamic images of the biodistribution of radioactive tracers in the brain. Through application of the principles of compartmental analysis, tracer uptake can be quantified in terms of specific physiological processes such as cerebral blood flow, cerebral metabolic rate, and the availability of receptors in brain. Whereas early PET studies in animal models of brain diseases were hampered by the limited spatial resolution of PET instruments, dedicated small-animal instruments now provide molecular images of rodent brain with resolution approaching 1mm, the theoretic limit of the method. Major applications of PET for brain research have consisted of studies of animal models of neurological disorders, notably Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD), stroke, epilepsy and traumatic brain injury; these studies have particularly benefited from selective neurochemical lesion models (PD), and also transgenic rodent models (AD, HD). Due to their complex and uncertain pathophysiologies, corresponding models of neuropsychiatric disorders have proven more difficult to establish. Historically, there has been an emphasis on PET studies of dopamine transmission, as assessed with a range of tracers targeting dopamine synthesis, plasma membrane transporters, and receptor binding sites. However, notable recent breakthroughs in molecular imaging include the development of greatly improved tracers for subtypes of serotonin, cannabinoid, and metabotropic glutamate receptors, as well as noradrenaline transporters, amyloid-β and neuroinflammatory changes. This article reviews the considerable recent progress in preclinical PET and discusses applications relevant to a number of neurological and neuropsychiatric disorders in humans.

What have positron emission tomography and 'Zippy' told us about the neuropharmacology of drug addiction?

Translational molecular imaging with positron emission tomography (PET) and allied technologies offer unrivalled applications in the discovery of biomarkers and aetiological mechanisms relevant to human disease. Foremost among clinical PET findings during the past two decades of addiction research is the seminal discovery of reduced dopamine D(2/3) receptor expression in the striatum of drug addicts, which could indicate a predisposing factor and/or compensatory reaction to the chronic abuse of stimulant drugs. In parallel, recent years have witnessed significant improvements in the performance of small animal tomographs (microPET) and a refinement of animal models of addiction based on clinically relevant diagnostic criteria. This review surveys the utility of PET in the elucidation of neuropharmacological mechanisms underlying drug addiction. It considers the consequences of chronic drug exposure on regional brain metabolism and neurotransmitter function and identifies those areas where further research is needed, especially concerning the implementation of PET tracers targeting neurotransmitter systems other than dopamine, which increasingly have been implicated in the pathophysiology of drug addiction. In addition, this review considers the causal effects of behavioural traits such as impulsivity and novelty/sensation-seeking on the emergence of compulsive drug-taking. Previous research indicates that spontaneously high-impulsive rats--as exemplified by 'Zippy'--are pre-disposed to escalate intravenous cocaine self-administration, and subsequently to develop compulsive drug taking tendencies that endure despite concurrent adverse consequences of such behaviour, just as in human addiction. The discovery using microPET of pre-existing differences in dopamine D(2/3) receptor expression in the striatum of high-impulsive rats suggests a neural endophenotype that may likewise pre-dispose to stimulant addiction in humans.

Association of clinical characteristics and cessation of tobacco, alcohol, and illicit drug use during pregnancy

Pregnancy is a time of relative urgency and opportunity for the treatment of substance use disorders in women, yet little is known about modifiable factors that contribute to successful abstinence. We examined self-worth, depression, anxiety, and novelty seeking in the context of substance use cessation during pregnancy in a sample of women with a high prevalence of substance abuse. Subjects were 448 birth mothers who participated in a prospective adoption study. Discontinuation rates were: tobacco 22.2%, alcohol 64.7%, marijuana 77.2%, and other drugs, 73.7-100%. Depression, anxiety, and novelty seeking were lower among women who discontinued substance use, compared to those who did not. Self-worth was higher in women who discontinued substance use. Among 110 polysubstance users, the number of substances discontinued during pregnancy was correlated with depression, anxiety, and self-worth in the hypothesized direction. Possible clinical implications are discussed. 

Behavioural addictions in bipolar disorder patients: role of impulsivity and personality dimensions

BACKGROUND

Behavioural addictions (BAs) can be understood as disorders characterized by repetitive occurrence of impulsive and uncontrolled behaviours. Very few studies have investigated their association with mood disorders. The present study was undertaken to determine the prevalence of the main behavioural addictions in a sample of bipolar outpatients in euthymic phase or stabilised by medications and to investigate the role of impulsivity and temperamental and character dimensions.

METHODS

One-hundred-fifty-eight Bipolar Disorder (BD) (DSM-IV) outpatients were assessed with tests designed to screen the main behavioural addictions: pathological gambling (SOGS), compulsive shopping (CBS), sexual (SAST), Internet (IAD), work (WART) and physical exercise (EAI) addictions. TCI-R and BIS-11 were administered to investigate impulsivity and personality dimensions mainly associated with BAs. The clinical sample has been compared with 200 matched healthy control subjects.

RESULTS

In bipolar patients, 33% presented at least one BA respect to the 13% of controls. Significantly higher scores at the scales for pathological gambling (p<.001), compulsive buying (p<.05), sexual (p<.001) and work addictions (p<.05) have been found. Self-Directness (p=.007) and Cooperativeness (p=.014) scores were significantly lower while impulsivity level was significantly higher (p=.007) in bipolar patients with BA than those without BA.

CONCLUSIONS

To our knowledge, this is the first study investigating the prevalence of behavioural addictions in BD showing a significant association of these disorders. BAs are more frequent in bipolar patients than in healthy controls and are related to higher impulsivity levels and character immaturity.

Psychotropic drug use among the elderly: risk factors involved in long-term use

This study explores the environmental, clinical, and personality factors that are associated with increased chronic psychotropic drug consumption in elderly patients. We collected data from 88 elderly individuals living in nursing homes, home-dwellings, and residential homes between December 2003 and June 2004. We assessed each subject's (1) current (previous four weeks) and chronic (>90 days) psychotropic drug consumption, (2) mood and anxiety (GHQ), and (3) personality (Temperament and Character Inventory). We found that 63% of the elderly subjects studied had used psychotropic drugs at least once and that one out of three elderly chronically consumed psychotropic drugs. Personality factors like harm avoidance and low level of persistence seem to be associated with chronic consumption.

Impulsivity characterization in the Roman high- and low-avoidance rat strains: behavioral and neurochemical differences

The selective breeding of Roman high- (RHA) and low-avoidance (RLA) rats for rapid vs extremely poor acquisition of active avoidance behavior in a shuttle-box has generated two phenotypes with different emotional and motivational profiles. The phenotypic traits of the Roman rat lines/strains (outbred or inbred, respectively) include differences in sensation/novelty seeking, anxiety/fearfulness, stress responsivity, and susceptibility to addictive substances. We designed this study to characterize differences between the inbred RHA-I and RLA-I strains in the impulsivity trait by evaluating different aspects of the multifaceted nature of impulsive behaviors using two different models of impulsivity, the delay-discounting task and five-choice serial reaction time (5-CSRT) task. Previously, rats were evaluated on a schedule-induced polydipsia (SIP) task that has been suggested as a model of obsessive-compulsive disorder. RHA-I rats showed an increased acquisition of the SIP task, higher choice impulsivity in the delay-discounting task, and poor inhibitory control as shown by increased premature responses in the 5-CSRT task. Therefore, RHA-I rats manifested an increased impulsivity phenotype compared with RLA-I rats. Moreover, these differences in impulsivity were associated with basal neurochemical differences in striatum and nucleus accumbens monoamines found between the two strains. These findings characterize the Roman rat strains as a valid model for studying the different aspects of impulsive behavior and for analyzing the mechanisms involved in individual predisposition to impulsivity and its related psychopathologies.

Melatonin as a potential therapeutic agent in psychiatric illness

The aim of this review was to summarize the potential use of melatonin in the treatment of mental disorders, specifically bipolar disorders, depression, and schizophrenia. To date, melatonin has been most commonly used in psychiatry because of its hypnotic, rhythm resynchronizing, and antioxidant actions. Here, we examine other properties of the melatonin including its anti-inflammatory, antinociceptive, anxiolytic, and drug detoxification actions as well as its protective effects against neural loss. The brain is an intricate sensory and motor organ which receives information from both the external and internal environments. It transduces information into complex chemical and electrical signals which are transmitted throughout the central nervous system (CNS) and the organism. The pathogenesis of mental disorders remains ambiguous and neuroinflammation has been proposed as a causative agent. We consider the potential contributions of melatonin as therapeutic agent in CNS and during neuroinflammation in mental disorders.

Dopamine receptors in the learning, memory and drug reward circuitry

As primary targets of a variety of abused drugs G-protein-coupled dopamine receptors in the brain play an important role in mediating the various drug-induced alterations in neural and psychological processes thought to underlie the transition from voluntary drug use to habitual and progressively compulsive drug-taking. This review considers the functional involvement of the five major dopamine receptor subtypes in drug reinforcement and reward and discusses the development of addiction as a series of learning transitions from initial goal-directed behaviour to pathological stimulus-response habits in which drug-seeking behaviours are automatically elicited and maintained by cues and stimuli associated with drug rewards.

High impulsivity predicts the switch to compulsive cocaine-taking

Both impulsivity and novelty-seeking have been suggested to be behavioral markers of the propensity to take addictive drugs. However, their relevance for the vulnerability to compulsively seek and take drugs, which is a hallmark feature of addiction, is unknown. We report here that, whereas high reactivity to novelty predicts the propensity to initiate cocaine self-administration, high impulsivity predicts the development of addiction-like behavior in rats, including persistent or compulsive drug-taking in the face of aversive outcomes. This study shows experimental evidence that a shift from impulsivity to compulsivity occurs during the development of addictive behavior, which provides insights into the genesis and neural mechanisms of drug addiction.

Modelling human drug abuse and addiction with dedicated small animal positron emission tomography

Drug addiction is a chronically relapsing brain disorder, which causes substantial harm to the addicted individual and society as a whole. Despite considerable research we still do not understand why some people appear particularly disposed to drug abuse and addiction, nor do we understand how frequently co-morbid brain disorders such as depression and attention-deficit hyperactivity disorder (ADHD) contribute causally to the emergence of addiction-like behaviour. In recent years positron emission tomography (PET) has come of age as a translational neuroimaging technique in the study of drug addiction, ADHD and other psychopathological states in humans. PET provides unparalleled quantitative assessment of the spatial distribution of radiolabelled molecules in the brain and because it is non-invasive permits longitudinal assessment of physiological parameters such as binding potential in the same subject over extended periods of time. However, whilst there are a burgeoning number of human PET experiments in ADHD and drug addiction there is presently a paucity of PET imaging studies in animals despite enormous advances in our understanding of the neurobiology of these disorders based on sophisticated animal models. This article highlights recent examples of successful cross-species convergence of findings from PET studies in the context of drug addiction and ADHD and identifies how small animal PET can more effectively be used to model complex psychiatric disorders involving at their core impaired behavioural self-control.

Personality profile in young current regular users of cocaine

This study examined the relationship between the personality profile of a sample of cocaine users and the presence of Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) diagnoses and the severity of substance use. A total of 120 participants (46 women, mean age: 23.8 years) from nonclinical settings in Barcelona, Spain, 2003-2006, were assessed using the Psychiatric Research Interview for Substance and Mental Disorders (PRISM) and the Temperament and Character Inventory-Revised version (TCI-R). Most of the participants had completed more than primary education, nearly half of them were employed, one third lived with parents, and near a quarter had some criminal record. Snorting was the main route of cocaine administration. They were using a mean of 1.82 substances. Cocaine users with low Self-Directedness, low Cooperativeness, and high Self-Transcendence scores in the TCI-R, with high severity of substance use and psychiatric comorbidity, would be suggestive of a possible specific phenotype. The limitations and implications of the study are discussed.

Gender-dependent association of the functional catechol-O-methyltransferase Val158Met genotype with sensation seeking personality trait

The gene encoding cathechol-O-methyltransferase (COMT) contains a common functional missense polymorphism (Val158Met) that regulates dopamine in an allele-dependent manner. A pivotal role of dopamine neurotransmission in the prefrontal cortex has been implicated in drug-seeking behavior and related personality traits, such as sensation seeking, with some evidence for a gender-specific association. Here, we tested the hypothesis that the COMT Val158Met polymorphism modulates the personality dimension, sensation seeking, in a gender-dependent manner. Study sample included 214 male (age 38.1+/-12.6 years) and 218 female (age 36.1+/-13.6 years) healthy volunteers, who were assessed with Zuckerman's sensation-seeking scale and genotyped for the Val158Met polymorphism (dbSNP:rs4680). Univariate analysis of variance showed that the sensation seeking score was significantly affected by a COMT genotype x gender interaction (F=5.330, df=2, p=0.005). The Val158Met polymorphism was associated with the sensation seeking personality trait in women only. The highest scores in the sensation-seeking scale and in three of the four subscales were observed in female subjects with the Val/Val genotype relative to women carrying the Met allele. Our results suggest that high COMT enzyme activity associated with the Val allele predisposes to high sensation seeking scores in female subjects and add to increasing evidence for a gender specific role of COMT in normal and dysfunctional behavior.

Nucleus accumbens D2/3 receptors predict trait impulsivity and cocaine reinforcement

Stimulant addiction is often linked to excessive risk taking, sensation seeking, and impulsivity, but in ways that are poorly understood. We report here that a form of impulsivity in rats predicts high rates of intravenous cocaine self-administration and is associated with changes in dopamine (DA) function before drug exposure. Using positron emission tomography, we demonstrated that D2/3 receptor availability is significantly reduced in the nucleus accumbens of impulsive rats that were never exposed to cocaine and that such effects are independent of DA release. These data demonstrate that trait impulsivity predicts cocaine reinforcement and that D2 receptor dysfunction in abstinent cocaine addicts may, in part, be determined by premorbid influences.