The association between the nicotinic acetylcholine receptor α4 subunit gene (CHRNA4) rs1044396 and Internet gaming disorder in Korean male adults

Neurotransmitters crosstalk and regulation in the reward circuit of subjects with behavioral addiction

Behavioral addictive disorders (BADs) have become a significant societal challenge over time. The central feature of BADs is the loss of control over engaging in and continuing behaviors, even when facing negative consequences. The neurobiological underpinnings of BADs primarily involve impairments in the reward circuitry, encompassing the ventral tegmental area, nucleus accumbens in the ventral striatum, and prefrontal cortex. These brain regions form networks that communicate through neurotransmitter signaling, leading to neurobiological changes in individuals with behavioral addictions. While dopamine has long been associated with the reward process, recent research highlights the role of other key neurotransmitters like serotonin, glutamate, and endorphins in BADs' development. These neurotransmitters interact within the reward circuitry, creating potential targets for therapeutic intervention. This improved understanding of neurotransmitter systems provides a foundation for developing targeted treatments and helps clinicians select personalized therapeutic approaches.

Association between the Taq1A polymorphism and problematic media use in preadolescent children

Objective

Problematic media use (PMU) is addiction-like media use. No study has examined if genetic factors for addiction relate to PMU during childhood. This study tested the association between genetic risk factors for addiction and PMU among 9-to-12-year-olds.

Method

Data were from a cohort of 9-to-12-year-olds recruited from Northern New England, 2018-2022, for a study examining obesity risk among children. Two polymorphisms related to dopaminergic (ANNK1 rs1800497 [the Taq1A polymorphism] and COMT rs4680) and one related to nicotinic (CHRNA4 rs1044396) pathways that were previously associated with internet addiction or internet video game addiction in adolescents and young adults were genotyped. Parent-reported PMU for children was measured with a validated nine-item scale (range for final scores: 1 to 5); higher scores indicate more severe PMU.

Results

Among children (n = 180; 43.9% female; 90.0% white, non-Hispanic; 82.2% of parents were college graduates), the median PMU score was 2.22 (IQR: 1.78, 2.78). In a linear regression model adjusted for child age, sex, European ancestry, and parent education, there was an additive association between the number of Taq1A1 alleles and PMU among children. Specifically, geometric mean PMU scores were 8.6% greater for each additional copy of the Taq1A1 allele (p = 0.030; R 2 = 5.2%). No other polymorphisms were statistically associated with PMU at the p < 0.05 level.

Conclusion

These preliminary findings suggest that a genetic predisposition to reduced dopamine sensitivity as indicated by the Taq1A polymorphism may relate to PMU in early adolescence. Findings need confirmation in larger samples.

Altered local intrinsic neural activity and molecular architecture in internet use disorders

BACKGROUND

Internet gaming disorder (IGD) is mainly characterized by its core dysfunction in higher-order brain cortices involved in inhibitory control, whose neurobiological basis remains unclear. Then, we will investigate local intrinsic neural activity (INA) alterations in IGD, ascertain whether these potential alterations are related to clinical characteristics, and further explore the underlying molecular architecture.

METHOD

In this study, we performed the fractional amplitude of low-frequency fluctuation (fALFF) and regional homogeneity (ReHo) derived from resting-state functional magnetic resonance imaging (rs-fMRI) to explore the impact of IGD on local INA. Correlation analysis revealed the relationship between ReHo and fALFF in terms of group differences and clinical characteristics. Moreover, correlations between fALFF, ReHo, and PET- and SPECT-driven maps were investigated to elucidate the specific molecular architecture alternations in IGD. Finally, receiver operating characteristic curve (ROC) analysis was used to show the potential abilities of fALFF and ReHo in distinguishing individuals with IGD (IGDs) from healthy controls (HCs).

RESULT

Compared with HCs, IGDs revealed increased ReHo and fALFF in the prefrontal cortex. Significantly decreased ReHo was observed in the temporal lobe, occipital lobe, and cerebellum. In addition, the ReHo values in the cerebellum_7b_R were positively correlated with internet addiction severity. ROC curve analysis showed that ReHo and fALFF-altered brain regions could effectively distinguish IGDs from HCs. More importantly, cross-modal correlations revealed local INA changes in brain regions associated with the monoamine neurotransmitter system and the less studied cholinergic/GABAergic system.

CONCLUSION

These results suggest that local functional impairments are shown in the audiovisual and inhibitory control circuits in IGDs. This may be associated with underlying neurotransmitter system alterations. Therefore, this study provides the possibility of GABAergic receptor agonists and cholinergic receptor inhibitors for the treatment of IGD.

Biomarkers of Internet Gaming Disorder-A Narrative Review

Since game mechanics and their visual aspects have become more and more addictive, there is concern about the growing prevalence of Internet gaming disorder (IGD). In the current narrative review, we searched PubMed and Google Scholar databases for the keywords "igd biomarker gaming" and terms related to biomarker modalities. The biomarkers we found are grouped into several categories based on a measurement method and are discussed in the light of theoretical addiction models (tripartite neurocognitive model, I-PACE). Both theories point to gaming-related problems with salience and inhibition. The first dysfunction makes an individual more susceptible to game stimuli (raised reward seeking), and the second negatively impacts resistance to these stimuli (decreased cognitive control). The IGD patients' hypersensitivity to reward manifests mostly in ventral striatum (VS) measurements. However, there is also empirical support for a ventral-to-dorsal striatal shift and transition from goal-directed to habitual behaviors. The deficits in executive control are demonstrated in parameters related to the prefrontal cortex (PFC), especially the dorsolateral prefrontal cortex (DLPFC). In general, the connection of PFC with reward under cortex nuclei seems to be dysregulated. Other biomarkers include reduced P3 amplitudes, high-frequency heart rate variability (HRV), and the number of eye blinks and saccadic eye movements during the non-resting state. A few studies propose a diagnostic (multimodal) model of IGD. The current review also comments on inconsistencies in findings in the nucleus accumbens (NAcc), anterior cingulate cortex (ACC), and precuneus and makes suggestions for future IGD studies.

Genetic Aspects of Problematic and Risky Internet Use in Young Men-Analysis of ANKK1, DRD2 and NTRK3 Gene Polymorphism

BACKGROUND

Internet addiction disorder (IAD) is characterized by an excess of uncontrolled preoccupations, urges, or behaviors related to computer use and Internet access that culminate in negative outcomes or individual distress. PIU includes excessive online activities (such as video gaming, social media use, streaming, pornography viewing, and shopping). The aim of this study was to analyze the association of gene polymorphisms that may influence the severity of risky behaviors in young men with the frequency of Internet use. We speculate that there are individual differences in the mechanisms of Internet addiction and that gene-hormone associations may represent useful biomarkers for subgroups of individuals.

MATERIALS AND METHODS

The study was conducted in a sample of 407 adult males. Subjects were asked to complete the Problematic Internet Use Test (PIUT). Serum was analyzed to determine concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone (TT), sex hormone binding protein (SHBG), dehydroepiandrosterone sulfate (DHEA-S), estradiol (E2), prolactin (PRL), insulin (I), serotonin (5-HT), and dopamine (DA), as well as DRD2, ANKK1, and NTRK3 gene polymorphisms.

RESULTS

In the analysis of the ANKK1 gene, there was a specific association between ANKK1 polymorphisms and PRL and 5-HT blood concentrations. There was also an association between the ANKK1 polymorphisms and LH and DA concentrations. When analyzing the DRD2 gene polymorphism, we found that in the group with a moderate level of Internet dependence, there was an association between both the G/GG and GG/GG polymorphisms and FSH concentration.

CONCLUSIONS

Our study found that there may be an association between the NTRK3 gene polymorphism and PIU. The polymorphisms of ANKK1 and DRD2 genes may be factors that influence the concentrations of hormones (PRL, 5-HT, DA) that are associated with the results obtained in PIU.

Neurobiological risk factors for problematic social media use as a specific form of Internet addiction: A narrative review

Problematic social media use (PSMU) is a behavioral addiction, a specific form of problematic Internet use associated with the uncontrolled use of social networks. It is typical mostly for modern adolescents and young adults, which are the first generations fully grown up in the era of total digitalization of society. The modern biopsychosocial model of the formation of behavioral addictions, postulating the impact of a large number of biological, psychological, and social factors on addictive behavior formation, may be quite applicable to PSMU. In this narrative review, we discussed neurobiological risk factors for Internet addiction with a focus on current evidence on the association between PSMU and structural/ functional characteristics of the brain and autonomic nervous system, neurochemical correlations, and genetic features. A review of the literature shows that the vast majority of the mentioned neurobiological studies were focused on computer games addiction and generalized Internet addiction (without taking into account the consumed content). Even though a certain number of neuroimaging studies have been conducted for PSMU, there is practically no research on neuropeptide and genetic associations for PSMU to date. This fact points to the extremely high relevance of such studies.

Gaming disorder: A summary of its characteristics and aetiology

The emergence, development, and maintenance of gaming disorder (GD) is the result of an interplay between gaming-related factors, individual factors, and environmental factors. None of these alone are sufficient to cause a disordered state, but it is the interactive co-occurrence of all these factors, which in some cases leads to GD. The goal of the present paper is to discuss in detail these three factors based on relevant and recent findings of the literature. Among gaming-related factors, we discuss online vs. offline videogames, the role of game genres, structural characteristics, game design elements, as well as some important monetization techniques. Among individual factors demographic risk factors, personality traits, motivational factors, comorbid psychopathology, genetic predisposition, and neurobiological processes are considered. Finally, among environmental factors we discuss family factors, early life experiences, the role of peers and school-related factors, as well as the broader context of culture including the popularity of esports.

Comparative Assessment of Outcomes in Drug Treatment for Smoking Cessation and Role of Genetic Polymorphisms of Human Nicotinic Acetylcholine Receptor Subunits

Objective: To investigate the effects of genetic polymorphisms of human nicotinic acetylcholine receptor subunits α3, α4 and α5, which are encoded by CHRNA3, CHRNA4 CHRNA5 genes, respectively, on nicotine addiction and outcomes of pharmacological treatments for smoking cessation.

Methods: A total of 143 smokers and 130 non-smokers were included. Genotyping for CHRNA3 rs578776, CHRNA4 rs1044396-rs1044397, CNRNA5 rs16969968 polymorphisms was performed by PCR, flowed by RFLP. Clinical outcomes and success rates of pharmacological treatments for smoking cessation with nicotine replacement therapy (NRT), bupropion or varenicline were determined at the 12th week of the treatment.

Results: Overall, 52 out of 143 (36.4%) smokers who received pharmacotherapy were able to quit smoking. Success rates for smoking cessation were similar for female (30.3%) and male (41.6%) subjects (p = 0.16). The success rate for smoking cessation treatment with varenicline (58.5%) was significantly higher as compared to other treatments with NRT (20.0%), bupropion (32.3%) or bupropion + NRT (40.0%) (chi-square test, p = 0.001). Smoker vs. non-smoker status and the clinical outcomes of drugs used for smoking cessation were found similar in subjects carrying wild-type and variant alleles of human nicotinic acetylcholine receptor α subunits.

Conclusion: In this study, smoking cessation treatment with varenicline was significantly more effective than treatments with nicotine replacement or bupropion in a cohort of Turkish subjects. Smoker/non-smoker status and the clinical outcomes of treatment with pharmacological agents were similar in subjects with wild-type or variant alleles for human nicotinic acetylcholine receptor subunits α3 (CHRNA3), α4 (CHRNA4) and α5 (CHRNA5).

Biochemical Correlates of Video Game Use: From Physiology to Pathology. A Narrative Review

In the last few decades, video game playing progressively became a widespread activity for many people, in childhood as well in adulthood. An increasing amount of literature has focused on pathological and non-pathological correlates of video game playing, with specific attention towards Internet Gaming Disorder (IGD). While many neurobiological studies in this field were based on neuroimaging, highlighting structural and functional brain changes among video game users, only a limited number of studies investigated the presence of biochemical correlates of video gaming. The present work aims to summarize and review the available literature about biochemical changes linked to video game use in IGD patients as well as non-pathological users, and the differences in between. Results may shed light on risks and benefits of video games, providing directions for further research on IGD treatment and, on other hand, on the potential role of video games in therapeutic or preventive protocols for specific conditions.

Roles of Hostility and Depression in the Association between the MAOA Gene Polymorphism and Internet Gaming Disorder

The metabolism of bioamine in the central nervous system contributes to the development of addiction. We examined the roles of hostility and depression in the association between internet gaming disorder (IGD) and monoamine oxidase-A (MAOA) EcoRV polymorphism (rs1137070). A total of 69 adults with IGD and 138 without IGD were recruited through diagnostic interviewing. We evaluated participants for rs1137070, depression, and hostility. The participants with the TT genotype of rs1137070 had a higher odds ratio of 2.52 (1.37–4.64) for IGD compared with the C carriers. Expressive hostility behavior and hostility cognition mediated the association between rs1137070 and IGD. Indicating lower MAOA activity, the TT genotype predicted IGD and higher expressive hostility behavior and hostility cognition. Expressive hostility behavior and hostility cognition may underline the association between rs1137070 and IGD. Assessment of and intervention for hostility behavior and cognition should be provided to attenuate the risk of IGD, particularly in those with the TT genotype. Further brain imaging or neurobiological studies are required to elucidate the possible mechanism underlying the association between MAOA activity and IGD.

Computational identification of putative common genomic drug and vaccine targets in Mycoplasma genitalium

Mycoplasma genitalium is an obligate intracellular bacterium that is responsible for several sexually transmitted infections, including non-gonococcal urethritis in men and several inflammatory reproductive tract syndromes in women. Here, we applied subtractive genomics and reverse vaccinology approaches for in silico prediction of potential vaccine and drug targets against five strains of M. genitalium. We identified 403 genes shared by all five strains, from which 104 non-host homologous proteins were selected, comprising of 44 exposed/secreted/membrane proteins and 60 cytoplasmic proteins. Based on the essentiality, functionality, and structure-based binding affinity, we finally predicted 19 (14 novel) putative vaccine and 7 (2 novel) candidate drug targets. The docking analysis showed six molecules from the ZINC database as promising drug candidates against the identified targets. Altogether, both vaccine candidates and drug targets identified here may contribute to the future development of therapeutic strategies to control the spread of M. genitalium worldwide.

Non-Substance Addiction in Childhood and Adolescence

BACKGROUND

Around 5.8% of adolescents and 2.8% of young adults have an Internet-related disorder. These figures underline the widespread concerns in our society regarding the potential dangers and risks associated with Internet and digital media use.

METHODS

Selective literature search for records on Internet-related disorders in children and adolescents.

RESULTS

Internet-related disorders are now viewed as belonging to the behavioral addiction. Research has revealed similarities to substance-related disorders. There are often associations with other mental illnesses such as depression, anxiety, attention deficit/hyperactivity disorder, and personality disorders, as well as disturbed sleep patterns, increased risk taking, nicotine abuse, an unbalanced diet, and lack of exercise. Female adolescents are statistically significantly more often affected than male adolescents (7.1% versus 4.5%). The German STICA study, the first randomized controlled trial worldwide, demonstrated that cognitive behavioral therapy was effective compared with a waiting group (odds ratio 10.10, 95% confidence interval [3.69; 27.65]).

CONCLUSION

Internet-related disorders have not yet been conclusively conceptualized and operationalized. Further work is urgently required to refine the concepts of both the illness and and its treatment.

Genetics of OCD and Related Disorders; Searching for Shared Factors

Obsessive compulsive disorder (OCD) and several other obsessive-compulsive related disorders (OCRDs) including hoarding disorder, body dysmorphic disorder (BDD), skin picking disorder, trichotillomania and the newly arising public health conditions of online gaming and gambling disorders, under the umbrella of Problematic Usage of the Internet (PUI), not only share some common phenotypes, but there is evidence to suggest share some genetic risk factors. The simple fact that these disorders segregate within families points to this notion. However, the current data are still scarce. This chapter focuses on identifying the shared genetic factors. To address this question, a systematic review of the literature investigating genetic findings in OCD and OCRDs including PUI was conducted, with a focus on their genetic similarities. Greater knowledge of the specific genetic risks shared among OCRDs would be expected to open new avenues in the understanding of the biological mechanisms causing the development of these phenotypes, as well as provide opportunities to develop new animal and cellular models testing new therapy avenues.

Molecular genetics of neurotransmitters and neuropeptides involved in Internet use disorders including first insights on a potential role of hypothalamus' oxytocin hormone

This chapter covers the phenomenon of Internet use disorders (IUDs) and putative associations with different neurotransmitter and neuropeptide systems. Genes coding for such messengers can be seen as an important starting point in the complicated quest to understand human behavior including new phenomena such as IUDs. Therefore, a special focus of this chapter will lie on individual differences in molecular genetic underpinnings of neurotransmitter and neuropeptide systems and their associations with individual differences in tendencies towards IUDs. By shedding light on these associations, putative predisposing molecular genetic factors for the emergence and maintenance of IUDs can be carved out. Therefore, first an introduction to IUDs and a model that can guide research on putative associations of IUDs with different specific neurotransmitters and neuropeptides will be presented. Subsequently, twin studies on the heritability of IUDs are reviewed. Finally, studies on differences in molecular genetic predispositions and their associations with differences in IUDs will be presented and discussed, including targets related to the dopaminergic and serotonergic system as well as the hypothalamic neuropeptide oxytocin. The chapter closes with a conclusion about what is already known and what needs to be investigated in future studies to gain further insights into putative associations between molecular genetic markers and IUDs.

Impulsivity across substance use categories: Consideration of sex/gender

PURPOSE OF REVIEW

The goal was to review recent (1/2015-2/2020) evidence of impulsivity as a feature of substance use disorders or use of substances (alcohol, cannabis, nicotine, opioids, stimulants) in males compared to females in terms of: a) impulsivity in substance-using groups (or substance-using compared to control groups), and b) relationship between impulsivity and substance use behavior, clinical severity, or treatment outcomes.

RECENT FINDINGS

Of 361 papers identified by the searches, 69 met inclusion criteria, and 39 were highlighted for considering sex/gender in relation to impulsivity in substance-using populations. Taken together, findings supported higher impulsivity in males and females who use substances, relative to controls; and higher impulsivity was linked with more substance use/severity in both sex/genders. There were mixed findings regarding male versus female differences in impulsivity among individuals who use substances, or in the magnitude of the relationship between impulsivity and substance use severity.

SUMMARY

The current body of evidence does not point to a consistent sex/gender difference in the role of impulsivity within and across substance use disorders. Impulsivity is a clinically-relevant construct for male and female individuals who use substances, across a range of substances.

Problematic internet use: an exploration of associations between cognition and COMT rs4818, rs4680 haplotypes

OBJECTIVE

Problematic internet users suffer from impairment in a variety of cognitive domains. Research suggests that COMT haplotypes exert differential effects on cognition. We sought to investigate differences in the genetic profiles of problematic internet users and whether those could shed light on potential cognitive differences.

METHODS

We recruited 206 non-treatment seeking participants with heightened impulsive traits and obtained cross-sectional demographic, clinical, and cognitive data as well as the genetic haplotypes of COMT rs4680 and rs4818. We identified 24 participants who presented with problematic internet use (PIU) and compared PIU and non-PIU participants using one-way analysis of variance (ANOVA) and chi square as appropriate.

RESULTS

PIU was associated with worse performance on decision making, rapid visual processing, and spatial working memory tasks. Genetic variants were associated with altered cognitive performance, but rates of PIU did not statistically differ for particular haplotypes of COMT.

CONCLUSION

This study indicates that PIU is characterized by deficits in decision making and working memory domains; it also provides evidence for elevated impulsive responses and impaired target detection on a sustained attention task, which is a novel area worth exploring further in future work. The effects observed in the genetic influences on cognition of PIU subjects imply that the genetic heritable components of PIU may not lie within the genetic loci influencing COMT function and cognitive performance; or that the genetic component in PIU involves many genetic polymorphisms each conferring only a small effect.

Clarifying terminologies in research on gaming disorder and other addictive behaviors: distinctions between core symptoms and underlying psychological processes

There exists ongoing debate regarding the clinical validity of single symptoms of and diagnostic criteria for gaming disorder. In particular, the potential symptom of gaming disorder that addresses coping with and escaping from negative feelings has received much attention and remains a focus of intensive discussion. We argue that it is important to consider differences or distinguish between, on the one hand, symptoms of and criteria for a disorder due to addictive behaviors, such as gaming disorder, versus, on the other hand, motivations, mechanisms, and psychological processes that may be involved in promoting addictive behaviors and that may explain symptom severity and course of the addictive disorder including potential treatment responses.

Neurobiological Risk Factors for the Development of Internet Addiction in Adolescents

The sudden appearance and spread of Internet addiction in adolescent populations, in association with the rapid escalation of consumed Internet content and the broad availability of smartphones and tablets with Internet access, is posing a new challenge for classical addictology which requires urgent solutions. Like the majority of other psychopathological conditions, pathological Internet addiction depends upon a group of multifactor polygenic conditions. For each specific case, there is a unique combination of inherited characteristics (nervous tissue structure, secretion, degradation, and reception of neuromediators), and many are extra-environment factors (family-related, social, and ethnic-cultural). One of the main challenges in the development of the bio-psychosocial model of Internet addiction is to determine which genes and neuromediators are responsible for increased addiction susceptibility. This information will herald the start of a search for new therapeutic targets and the development of early prevention strategies, including the assessment of genetic risk levels. This review summarizes the literature and currently available knowledge related to neurobiological risk factors regarding Internet addiction in adolescents. Genetic, neurochemical and neuroimaging data are presented with links to actual pathogenetic hypotheses according to the bio-psychosocial model of IA forming.

Brain and Cognition for Addiction Medicine: From Prevention to Recovery Neural Substrates for Treatment of Psychostimulant-Induced Cognitive Deficits

Addiction to psychostimulants like cocaine, methamphetamine, and nicotine poses a continuing medical and social challenge both in the United States and all over the world. Despite a desire to quit drug use, return to drug use after a period of abstinence is a common problem among individuals dependent on psychostimulants. Recovery for psychostimulant drug-dependent individuals is particularly challenging because psychostimulant drugs induce significant changes in brain regions associated with cognitive functions leading to cognitive deficits. These cognitive deficits include impairments in learning/memory, poor decision making, and impaired control of behavioral output. Importantly, these drug-induced cognitive deficits often impact adherence to addiction treatment programs and predispose abstinent addicts to drug use relapse. Additionally, these cognitive deficits impact effective social and professional rehabilitation of abstinent addicts. The goal of this paper is to review neural substrates based on animal studies that could be pharmacologically targeted to reverse psychostimulant-induced cognitive deficits such as impulsivity and impairment in learning and memory. Further, the review will discuss neural substrates that could be used to facilitate extinction learning and thus reduce emotional and behavioral responses to drug-associated cues. Moreover, the review will discuss some non-pharmacological approaches that could be used either alone or in combination with pharmacological compounds to treat the above-mentioned cognitive deficits. Psychostimulant addiction treatment, which includes treatment for cognitive deficits, will help promote abstinence and allow for better rehabilitation and integration of abstinent individuals into society.

Manifesto for a European research network into Problematic Usage of the Internet

The Internet is now all-pervasive across much of the globe. While it has positive uses (e.g. prompt access to information, rapid news dissemination), many individuals develop Problematic Use of the Internet (PUI), an umbrella term incorporating a range of repetitive impairing behaviours. The Internet can act as a conduit for, and may contribute to, functionally impairing behaviours including excessive and compulsive video gaming, compulsive sexual behaviour, buying, gambling, streaming or social networks use. There is growing public and National health authority concern about the health and societal costs of PUI across the lifespan. Gaming Disorder is being considered for inclusion as a mental disorder in diagnostic classification systems, and was listed in the ICD-11 version released for consideration by Member States (http://www.who.int/classifications/icd/revision/timeline/en/). More research is needed into disorder definitions, validation of clinical tools, prevalence, clinical parameters, brain-based biology, socio-health-economic impact, and empirically validated intervention and policy approaches. Potential cultural differences in the magnitudes and natures of types and patterns of PUI need to be better understood, to inform optimal health policy and service development. To this end, the EU under Horizon 2020 has launched a new four-year European Cooperation in Science and Technology (COST) Action Programme (CA 16207), bringing together scientists and clinicians from across the fields of impulsive, compulsive, and addictive disorders, to advance networked interdisciplinary research into PUI across Europe and beyond, ultimately seeking to inform regulatory policies and clinical practice. This paper describes nine critical and achievable research priorities identified by the Network, needed in order to advance understanding of PUI, with a view towards identifying vulnerable individuals for early intervention. The network shall enable collaborative research networks, shared multinational databases, multicentre studies and joint publications.