Publication trends in addiction research

Ghrelin and impulsivity relationship in alcohol-dependent patients and healthy individuals

AIMS

Abundant research indicates that ghrelin hormone levels are associated with alcohol use and addiction. One of the mediators of this association may be impulsivity, which is one of the common traits observed in alcohol addiction and some eating disorders. This study evaluated participants with alcohol dependency and healthy volunteers to determine whether trait impulsivity and ghrelin levels are associated.

METHODS

This study analyzed trait impulsivity scores and fasting serum ghrelin levels of 44 males with alcohol dependency and 48 healthy male participants. The Barratt Impulsiveness Scale and the UPPS Impulsive Behaviour Scale (UPPS) were used to measure trait impulsivity levels. Penn Alcohol Craving Scale and Yale Brown Obsessive Compulsive Drinking Scale for heavy drinking were used to assess craving at the baseline and after the detoxification period.

RESULTS

Alcohol-dependent patients' fasting ghrelin levels were significantly higher than that of healthy participants. Ghrelin plasma levels were positively correlated with UPPS total impulsivity scores and sensation-seeking among healthy individuals. In alcohol-dependent participants, there was a positive correlation between UPPS urgency scores obtained at the baseline and fasting ghrelin levels before and after the detoxification period.

CONCLUSIONS

Ghrelin-impulsivity relationship could be observed in certain dimensions of impulsivity in both alcohol-dependent and healthy individuals and even independent of the effect of alcohol. Although the associated impulsivity dimensions differ in different groups, the results are parallel to other studies in terms of demonstrating the relationship between ghrelin and impulsivity.

Gender parity and homophily in the Drug and Alcohol Dependence editorial process

BACKGROUND

Despite efforts towards gender parity and some improvement over time, gender bias in peer review remains a pervasive issue. We examined gender representation and homophily in the peer review process for Drug and Alcohol Dependence (DAD).

METHODS

We extracted data for papers submitted to DAD between 2004 and 2019, inclusive. Inferred gender was assigned to handling editors and reviewers using the NamSor gender inference Application Programming Interface (API).

RESULTS

Men and women handling editors were approximately equally likely to invite women reviewers over time, with only a few exceptions. Over time, 47.1% of editors were women, and 42.6% of review invitations were sent to women. Men were largely consistent over time in their likelihood of accepting a review invitation, while the likelihood of women accepting a review invitation was more variable over time. Gender differences in rates of accepting a review invitation were minimal; however, as women approached half of all invited reviewers in recent years, there has been a greater trend for women, relative to men, to decline review invitations. Evidence of homophily on the part of reviewers accepting invitations was minimal, but in certain years, a tendency to accept review invitations at higher rates from editors of the same gender was observed.

DISCUSSION

Given the benefits of diversity in scientific advancement, these results underline the importance of continuing efforts to increase gender diversity among editors and in reviewer pools, and the need for reviewers to be mindful of their own reviewing practices.

Circulating ghrelin changes as a biomarker of the stress response and craving in abstinent smokers

RATIONALE

There has been growing interest in the role of ghrelin in stress and addiction. Ghrelin regulates central reward mechanisms by mediating the mesolimbic dopaminergic system. Stress also induces neurophysiological activations related to drug reward. However, the extent to which psychosocial stress is associated with changes in ghrelin levels has not been tested in individuals with nicotine dependency undergoing withdrawal, a condition known to induce stress-like symptoms.

OBJECTIVES

We investigated the association of stress-induced ghrelin, craving, and smoking lapse.

METHODS

Thirty-six smokers attended a laboratory session that included acute stress tasks during the initial phase of quitting. Self-report measures and biochemical samples were collected for the assessment of smoking status. Blood samples for the measurement of ghrelin and self-report measures of craving were collected multiple times throughout the session RESULTS: Multivariate analysis of variance controlling for gender found a significant main effect of sampling time and lapse group (p < 0.05). Ghrelin levels significantly increased over the pre-stress and post-stress periods (ps < 0.001), suggesting a delayed stress response. Those who lapsed during the study had higher ghrelin levels than those who were able to successfully abstain. A ghrelin stress response was calculated and a significant association was found between this response and craving, which changed across time points (ps < 0.008).

CONCLUSIONS

The results of this study demonstrate that ghrelin is sensitive to acute manipulation of stress and that there is potential usefulness for ghrelin as a marker of stress, craving, and smoking lapse.

Investigación española en las áreas de adicciones y de trastornos de la alimentación: análisis de la producción, colaboración e impacto científico (1962-2017)

Las adicciones y los trastornos de la alimentación constituyen uno de los principales problemas de salud en la sociedad contemporánea al que se destinan gran cantidad de recursos destinados a la investigación para su prevención y tratamiento. Objetivos. Analizar la investigación española en el área de adicciones y trastornos de la alimentación desde que se publicó el primer trabajo recogido en bases de datos bibliográficas y desde una perspectiva bibliométrica. Metodología. Para obtener la información necesaria se consultaron las bases de datos Web of Science, Scopus y bases de datos del CSIC. Se elaboró un perfil de búsqueda específico. Se obtuvieron indicadores bibliométricos de producción, colaboración e impacto científico. Se utilizó el análisis de redes sociales para identificar las redes de investigadores y sus relaciones de colaboración, así como la red de co-palabras clave. Resultados. La producción científica aumentó progresivamente durante los casi 50 años analizados. Los trabajos se publicaron en una gran variedad de revistas nacionales y extranjeras, entre las que destacaron Adicciones, Revista Española de Drogodependencias, Trastornos Adictivos y Salud y Drogas. Conclusiones. La producción, colaboración e impacto de la investigación ha sido creciente y las adicciones más estudiadas fueron el tabaquismo, alcoholismo, consumo de cocaína y consumo de anfetaminas.

Global Scientific Production on Illicit Drug Addiction: A Two-Decade Analysis

AIMS

Addiction science has made great progress in the past decades. We conducted a scientometric study in order to quantify the number of publications and the growth rate globally, regionally, and at country levels.

METHODS

In October 2015, we searched the Scopus database using the general keywords of addiction or drug-use disorders combined with specific terms regarding 4 groups of illicit drugs - cannabis, opioids, cocaine, and other stimulants or hallucinogens. All documents published during the 20-year period from 1995 to 2014 were included.

RESULTS

A total of 95,398 documents were retrieved. The highest number of documents were on opioids, both globally (60.1%) and in each of 5 continents. However, studies on cannabis showed a higher growth rate in the last 5-year period of the study (2010-2014). The United States, the United Kingdom, Germany, Canada, Australia, France, Spain, Italy, China, and Japan - almost all studies were from high-income countries - occupied the top 10 positions and produced 81.4% of the global science on drug addiction.

CONCLUSION

As there are important socio-cultural differences in the epidemiology and optimal clinical care of addictive disorders, it is suggested that low- and more affected middle-income countries increase their capacity to conduct research and disseminate the knowledge in this field.

Quantification of alcohol drinking patterns in mice

The use of mice in alcohol research provides an excellent model system for a better understanding of the genetics and neurobiology of alcohol addiction. Almost 60 years ago, alcohol researchers began to test strains of mice for alcohol preference and intake. In particular, various voluntary alcohol drinking paradigms in the home cage were developed. In mouse models of voluntary oral alcohol consumption, animals have concurrent access to water and either one or several concentrated alcohol solutions in their home cages. Although these models have high face validity, many experimental conditions require a more precise monitoring of alcohol consumption in mice in order to capture the role of specific strains or genes, or any other manipulation on alcohol drinking behavior. Therefore, we have developed a fully automated, highly precise monitoring system for alcohol drinking in mice in the home cage. This system is now commercially available. We show that this drinkometer system allows for detecting differences in drinking behavior (i) in transgenic mice, (ii) following alcohol deprivation, and (iii) following stress applications that are usually not detected by classical home-cage drinking paradigms. In conclusion, our drinkometer system allows disturbance-free and high resolution monitoring of alcohol drinking behavior. In particular, micro-drinking and circadian drinking patterns can be monitored in genetically modified and inbred strains of mice after environmental and pharmacological manipulation, and therefore this system represents an improvement in measuring behavioral features that are of relevance for the development of alcohol use disorders.

Bibliometric analysis on global Catha edulis (khat) research production during the period of 1952-2014

BACKGROUND

Publication of scientific articles related to khat (Catha edulis) in peer-reviewed journals is considered a measure of research productivity. The principal objectives of this study were to quantify the research contribution related to khat at the global level, as well as to determine its relative growth rate, collaborative measures taken, productivity at the institutional level, and the most prolific journals publishing on the topic.

METHODS

On the basis of title words related to khat, publications were identified for all data in Scopus bibliographic database's history up to December 31, 2014. The research productivity for the top 10 countries was evaluated in relation to the population size and gross domestic product (GDP) in 2013.

RESULTS

The criteria were met by 651documents published in 51 countries. The largest number of articles associated with khat was from the UK (15.2 %), followed by Yemen (10.3 %), the USA (9.7 %) and Ethiopia (9.1 %). Ethiopia, Yemen, and Kenya had the highest productivity of publications after standardization by population size and GDP. Furthermore, Yemen achieved the highest number of collaborations, by having researchers from 19 countries. Ethiopia followed, having researchers from 16 countries.

CONCLUSIONS

This bibliometric study provides a demonstration for the worldwide research activity regarding khat. The number of articles related to khat has increased rapidly over the last 10 years. The present study is a good starting point to evaluate research activity in the field of khat. Although the data shows a promising increase in the research activity, the quantity of khat-related research is still too little compared to the massive use of khat in certain countries.

Convergent functional genomics in addiction research - a translational approach to study candidate genes and gene networks

Convergent functional genomics (CFG) is a translational methodology that integrates in a Bayesian fashion multiple lines of evidence from studies in human and animal models to get a better understanding of the genetics of a disease or pathological behavior. Here the integration of data sets that derive from forward genetics in animals and genetic association studies including genome wide association studies (GWAS) in humans is described for addictive behavior. The aim of forward genetics in animals and association studies in humans is to identify mutations (e.g. SNPs) that produce a certain phenotype; i.e. "from phenotype to genotype". Most powerful in terms of forward genetics is combined quantitative trait loci (QTL) analysis and gene expression profiling in recombinant inbreed rodent lines or genetically selected animals for a specific phenotype, e.g. high vs. low drug consumption. By Bayesian scoring genomic information from forward genetics in animals is then combined with human GWAS data on a similar addiction-relevant phenotype. This integrative approach generates a robust candidate gene list that has to be functionally validated by means of reverse genetics in animals; i.e. "from genotype to phenotype". It is proposed that studying addiction relevant phenotypes and endophenotypes by this CFG approach will allow a better determination of the genetics of addictive behavior.

A systems medicine research approach for studying alcohol addiction

According to the World Health Organization, about 2 billion people drink alcohol. Excessive alcohol consumption can result in alcohol addiction, which is one of the most prevalent neuropsychiatric diseases afflicting our society today. Prevention and intervention of alcohol binging in adolescents and treatment of alcoholism are major unmet challenges affecting our health-care system and society alike. Our newly formed German SysMedAlcoholism consortium is using a new systems medicine approach and intends (1) to define individual neurobehavioral risk profiles in adolescents that are predictive of alcohol use disorders later in life and (2) to identify new pharmacological targets and molecules for the treatment of alcoholism. To achieve these goals, we will use omics-information from epigenomics, genetics transcriptomics, neurodynamics, global neurochemical connectomes and neuroimaging (IMAGEN; Schumann et al. ) to feed mathematical prediction modules provided by two Bernstein Centers for Computational Neurosciences (Berlin and Heidelberg/Mannheim), the results of which will subsequently be functionally validated in independent clinical samples and appropriate animal models. This approach will lead to new early intervention strategies and identify innovative molecules for relapse prevention that will be tested in experimental human studies. This research program will ultimately help in consolidating addiction research clusters in Germany that can effectively conduct large clinical trials, implement early intervention strategies and impact political and healthcare decision makers.

The role of ghrelin in drug and natural reward

Ghrelin is a protein that has been given special attention in both nutrition and addiction research during the last decade. Consequently, a vast amount of information has been accumulated concerning the role of ghrelin in natural and drug reward. We are now in the position to ask whether the ghrelin system could be targeted to treat maladaptive behaviours such as obesity and drug addiction. Indeed, ghrelin research has demonstrated that blocking the activity of ghrelin receptors may be effective in reducing the consumption of both food and drugs of abuse. This review will give a short overview of our current knowledge about the ghrelin system in the context of drug and natural rewards as well as the possibility of developing potential ghrelin-based treatments.

Neurocircuitry for modeling drug effects

The identification and functional understanding of the neurocircuitry that mediates alcohol and drug effects that are relevant for the development of addictive behavior is a fundamental challenge in addiction research. Here we introduce an assumption-free construction of a neurocircuitry that mediates acute and chronic drug effects on neurotransmitter dynamics that is solely based on rodent neuroanatomy. Two types of data were considered for constructing the neurocircuitry: (1) information on the cytoarchitecture and neurochemical connectivity of each brain region of interest obtained from different neuroanatomical techniques; (2) information on the functional relevance of each region of interest with respect to alcohol and drug effects. We used mathematical data mining and hierarchical clustering methods to achieve the highest standards in the preprocessing of these data. Using this approach, a dynamical network of high molecular and spatial resolution containing 19 brain regions and seven neurotransmitter systems was obtained. Further graph theoretical analysis suggests that the neurocircuitry is connected and cannot be separated into further components. Our analysis also reveals the existence of a principal core subcircuit comprised of nine brain regions: the prefrontal cortex, insular cortex, nucleus accumbens, hypothalamus, amygdala, thalamus, substantia nigra, ventral tegmental area and raphe nuclei. Finally, by means of algebraic criteria for synchronizability of the neurocircuitry, the suitability for in silico modeling of acute and chronic drug effects is indicated. Indeed, we introduced as an example a dynamical system for modeling the effects of acute ethanol administration in rats and obtained an increase in dopamine release in the nucleus accumbens-a hallmark of drug reinforcement-to an extent similar to that seen in numerous microdialysis studies. We conclude that the present neurocircuitry provides a structural and dynamical framework for large-scale mathematical models and will help to predict chronic drug effects on brain function.

The use of a novel drinkometer system for assessing pharmacological treatment effects on ethanol consumption in rats

BACKGROUND

There are numerous studies in the preclinical alcohol research field showing that pharmacological interventions and many other manipulations can influence ethanol (EtOH) consumption in a free-choice paradigm in rats. Most of these studies are based on 24-hour measurements. These studies provide a measure of the total amount of EtOH consumed per day, but do not provide information on the drinking patterns within this period of measurement. Here, we used a novel drinkometer system in combination with Fourier analysis to provide detailed information on drinking patterns.

METHODS

Our automated drinkometer system measures fluid consumption by means of high-precision sensors attached to the drinking bottles in the home cage of the rat and thereby ameliorates several limitations of a classical lickometer-based drinkometer system. As an example of its application, we used the alcohol deprivation effect (ADE) model for relapse-like drinking and tested as a reference compound lamotrigine, which has a robust effect on the ADE. Fourier analysis was chosen as the main strategy for 24-hour drinking pattern recognition during water/EtOH drinking.

RESULTS

Under baseline conditions, voluntary EtOH consumption in rats can be expressed as characteristic oscillations that follow diurnal activity and differ in their amplitude, depending on the EtOH concentration. This diurnal drinking rhythmicity was altered during a relapse condition. Furthermore, lamotrigine given during the ADE did not significantly affect the drinking frequency or the number of approaches to the EtOH bottles when compared to vehicle-treated animals. However, EtOH intake during a drinking approach was dramatically reduced.

CONCLUSIONS

The use of the drinkometer system and mathematical modeling allows the characterization of treatment effects on relapse-like drinking with a great level of detail. One use of such detailed information may lie in its translational predictability. For instance, owing to lamotrigine treatment's lack of effect on EtOH drinking frequency or the number of approaches to the EtOH bottles, this compound might not be effective in relapse prevention per se but may reduce hedonic EtOH effects and could therefore be used in alcohol-dependent patients if harm reduction is the primary goal of treatment.