Are there genetic influences on addiction: evidence from family, adoption and twin studies

Intergenerational transmission of alcohol misuse: mediation and interaction by school performance in a Swedish birth cohort

BACKGROUND

Children whose parents misuse alcohol have increased risks of own alcohol misuse in adulthood. Though most attain lower school marks, some still perform well in school, which could be an indicator of resilience with protective potential against negative health outcomes. Accordingly, the aim of this study was to examine the processes of mediation and interaction by school performance regarding the intergenerational transmission of alcohol misuse.

METHODS

Data were drawn from a prospective Swedish cohort study of children born in 1953 (n=14 608). Associations between parental alcohol misuse (ages 0-19) and participants' own alcohol misuse in adulthood (ages 20-63) were examined by means of Cox regression analysis. Four-way decomposition was used to explore mediation and interaction by school performance in grade 6 (age 13), grade 9 (age 16) and grade 12 (age 19).

RESULTS

Mediation and/or interaction by school performance accounted for a substantial proportion of the association between parental alcohol misuse and own alcohol misuse in adulthood (58% for performance in grade 6, 27% for grade 9 and 30% for grade 12). Moreover, interaction effects appeared to be more important for the outcome than mediation.

CONCLUSION

Above-average school performance among children whose parents misused alcohol seems to reflect processes of resilience with the potential to break the intergenerational transmission of alcohol misuse. Four-way decomposition offers a viable approach to disentangle processes of interaction from mediation, representing a promising avenue for future longitudinal research.

Convergent Evidence for Predispositional Effects of Brain Gray Matter Volume on Alcohol Consumption

BACKGROUND

Alcohol use has been reliably associated with smaller subcortical and cortical regional gray matter volumes (GMVs). Whether these associations reflect shared predisposing risk factors or causal consequences of alcohol use remains poorly understood.

METHODS

Data came from 3 neuroimaging samples (N = 2423), spanning childhood or adolescence to middle age, with prospective or family-based data. First, we identified replicable GMV correlates of alcohol use. Next, we used family-based and longitudinal data to test whether these associations may plausibly reflect a predispositional liability for alcohol use or a causal consequence of alcohol use. Finally, we used heritability, gene-set enrichment, and transcriptome-wide association study approaches to evaluate whether genome-wide association study-defined genomic risk for alcohol consumption is enriched for genes that are preferentially expressed in regions that were identified in our neuroimaging analyses.

RESULTS

Smaller right dorsolateral prefrontal cortex (DLPFC) (i.e., middle and superior frontal gyri) and insula GMVs were associated with increased alcohol use across samples. Family-based and prospective longitudinal data suggest that these associations are genetically conferred and that DLPFC GMV prospectively predicts future use and initiation. Genomic risk for alcohol use was enriched in gene sets that were preferentially expressed in the DLPFC and was associated with replicable differential gene expression in the DLPFC.

CONCLUSIONS

These data suggest that smaller DLPFC and insula GMV plausibly represent genetically conferred predispositional risk factors for, as opposed to consequences of, alcohol use. DLPFC and insula GMV represent promising biomarkers for alcohol-consumption liability and related psychiatric and behavioral phenotypes.

Associations between major depressive symptoms and drinking onset: Do sex and age matter?

BACKGROUND

There has been mixed evidence about whether major depression predicts drinking onset. Empirical evidence about whether the heterogeneity of major depressive symptoms differentially predicts drinking onset is scarce, and potential sex- and age-variations have not been fully studied. In this study, we estimate sex- and age-specific relationships linking (a) depressed mood and/or anhedonia with drinking onset among all 'at-risk' individuals and (b) three latent depressive constructs, manifested by 13 clinical features, with drinking onset among individuals with depressed mood and/or anhedonia.

METHODS

Study population was non-institutionalized civilian residents 12 years of age and older living in the United States. Major depressive symptoms and drinking onset were assessed via audio-computer-assisted self-interviews. Logistic regressions and structural equation modeling were used for analysis.

RESULTS

Among all 'at risk' individuals, depressed mood or anhedonia strongly predicted early-adolescent drinking onset, whereas they did not predict at-age drinking onset. Among individuals with depressed mood or anhedonia, a 3-factor model provided a good fit to the data for all sex- and age-subgroups. With the exception of early-adolescent boys, neurovegetative symptoms and suicide-related symptoms tended to positively predict underage drinking onset, whereas Low mood or energy tended to inversely predict underage drinking onset; limited evidence was found for at-age and post-21 drinking onset.

LIMITATIONS

The observational nature precludes causal inference. Few people initiated alcohol drinking later than 21 years of age, which resulted in less precise estimates.

CONCLUSIONS

Strengths and directions of major depressive symptoms predicting drinking onset vary across age, sex, and depressive symptoms.

Parental and life-course influences on symptomatic airflow obstruction

Few studies have examined the contribution of life-course factors in explaining familial aggregation of chronic lung conditions. Using data from the 1958 British Birth Cohort, a life-course approach was used to examine whether, and how, exposure to risk factors through one's life explained the association between parental respiratory disease history and symptomatic airflow obstruction (AO). Cohort participants (n=6212) were characterised in terms of parental respiratory disease history and symptomatic AO at 45 years. Life-course factors (e.g. smoking, asthma and early-life factors) were operationalised as life period-specific and cumulative measures. Logistic regression and path analytic models predicting symptomatic AO adjusted for parental respiratory disease history were used to test different life-course models (critical period, accumulation- and chain-of-risks models). While some life-course factors (e.g. childhood passive smoking and occupational exposure) were individually associated with parental respiratory disease history and symptomatic AO, asthma (OR 6.44, 95% CI 5.01–8.27) and persistent smoking in adulthood (OR 5.42, 95% CI 4.19–7.01) had greater impact on the association between parental respiratory disease history and symptomatic AO. A critical period model provided a better model fit compared with an accumulation-of-risk model and explained 57% of the effect of parental respiratory disease history on symptomatic AO. Adulthood asthma and smoking status explained around half of the effect of parental respiratory disease history on chronic obstructive pulmonary disease. Beyond smoking history, the combination of parental respiratory disease history and adulthood asthma may provide an opportunity for early diagnosis and intervention.

Adulthood asthma and smoking explain half of the effect of parental respiratory disease history on symptomatic airflow obstruction. Use of a life-course approach and models may help clarify mechanisms behind associations in intergenerational lung health.http://bit.ly/2PIzGf4

Association of parental substance use disorder with offspring cognition: a population family-based study

AIMS

To assess whether parental substance use disorder (SUD) is associated with lower cognitive ability in offspring, and whether the association is independent of shared genetic factors.

DESIGN

A population family-based cohort study utilizing national Swedish registries. Linear regression with increased adjustment of covariates was performed in the full population. In addition, the mechanism of the association was investigated with children-of-sibling analyses using fixed-effects regression with three types of sibling parents with increasing genetic relatedness (half-siblings, full siblings and monozygotic twins).

SETTING AND PARTICIPANTS

A total of 3 004 401 people born in Sweden between 1951 and 1998.

MEASUREMENTS

The exposure variable was parental SUD, operationalized as having a parent with life-time SUD diagnosis or substance-related criminal conviction in the National Patient Register or Crime Register, respectively. Outcomes were cognitive test score at military conscription and final school grades when graduating from compulsory school. Covariates included in the analyses were sex, birth year, parental education, parental migration status and parental psychiatric comorbid diagnoses.

FINDINGS

In the full population, parental SUD was associated with decreased cognitive test stanine scores at conscription [4.56, 95% confidence interval (CI) = 4.55-4.57] and lower Z-standardized school grades (-0.43, 95% CI = -0.43 to -0.42) compared to people with no parental SUD (cognitive test: 5.17, 95% CI = 5.17-5.18; grades: 0.09, 95% CI = 0.08-0.09). There was evidence of a dose-response relationship, in that having two parents with SUD (cognitive test: 4.17, 95% CI = 4.15-4.20; grades: -0.83, 95% CI = -0.84 to -0.82) was associated with even lower cognitive ability than having one parent with SUD (cognitive test: 4.60, 95% CI = 4.59-4.60; grades: -0.38, 95% CI = -0.39 to -0.380). In the children-of-siblings analyses when accounting for genetic relatedness, these negative associations were attenuated, suggestive of shared underlying genetic factors.

CONCLUSIONS

There appear to be shared genetic factors between parental substance use disorder (SUD) and offspring cognitive function, suggesting that cognitive deficits may constitute a genetically transmitted risk factor in SUD.

White matter connectometry among individuals with self-reported family history of drug and alcohol use disorders

Heredity is an important risk factor for alcoholism. Several studies have been conducted on small groups of alcohol naïve adolescents which show lowered fractional anisotropy of frontal white matter in individuals with a family history of alcohol and substance use disorder (FH+). We compare large adult FH+ and FH- groups using white matter connectometry, different from the previously used global tractography method, as it is more sensitive to regional variability. Imaging and behavioral data from the Human Connectome Project (WU-MINN HCP 1200) was analyzed. Groups of participants were positive (n = 109) and negative (n = 109) for self-reported alcohol and substance use disorders in at least one parent, and stringently matched. Connectometry was performed on diffusion MRI in DSI-Studio using q-space diffeomorphic reconstruction, and multiple regression was completed with 5000 permutations. Analyses showed decreased major tract (>40 mm) connectivity in the FH+ group in left inferior longitudinal fasciculus, bilateral cortico-striatal pathway, left cortico-thalamic pathway, and corpus callosum, compared to the FH- group. For cognitive tasks related to reward processing, inhibition, and monitoring, there were a number of interactions, such that the relationship between identified tracts and behavior differed significantly between groups. Self-reported family history was associated with decreased connectivity in reward signaling pathways, controlling for alcohol consumption and alcohol use disorder. This is the first connectometry study of FH+, and extends the neural basis of the hereditary diathesis of alcoholism beyond that demonstrated with global tractography. Regions associated with FH+ are similar to those associated with alcohol use disorder.

Genome-Wide DNA Methylation Analysis in Male Methamphetamine Users With Different Addiction Qualities

This paper aimed to explore the genome-wide DNA methylation status of methamphetamine (MA) abusers with different qualities to addiction and to identify differentially methylated candidate genes. A total of 207 male MA abusers with an MA abuse frequency of ≥10 times and an MA abuse duration of ≥1 year were assigned to the high MA addiction quality group (HMAQ group; 168 subjects who met the diagnostic criteria for MA dependence according to the DSM-IV) or to the low MA addictive quality group (LMAQ group; 39 subjects who did not meet the criteria for MA dependence). In addition 105 healthy controls were recruited. Eight HMAQ subjects, eight LMAQ subjects, and eight healthy controls underwent genome-wide DNA methylation scans with an Infinium Human Methylation 450 array (Illumina). The differentially methylated region (DMR) data were entered into pathway analysis, and the differentially methylated position (DMP) data were screened for candidate genes and verified by MethyLight qPCR with all samples. Seven specific pathways with an abnormal methylation status were identified, including the circadian entrainment, cholinergic synapse, glutamatergic synapse, retrograde endocannabinoid signaling, GABAergic synapse, morphine addiction and PI3K-Akt signaling pathways. SLC1A6, BHLHB9, LYNX1, CAV2, and PCSK9 showed differences in their methylation levels in the three groups. Only the number of methylated copies of CAV2 was significantly higher in the LMAQ group than in the HMAQ group. Our findings suggest that the circadian entrainment pathway and the caveolin-2 gene may play key roles in MA addiction quality. Further studies on their functions and mechanisms will help us to better understand the pathogenesis of MA addiction and to explore new targets for drug intervention.

Fathers' alcohol use and suicidal behaviour in offspring during youth and young adulthood

OBJECTIVE

To examine the association between various indicators of father's alcohol use and suicidal behaviour in offspring during youth and young adulthood.

METHODS

The study is based on a cohort of 68 910 Swedish citizens who were born between 1970 and 1985 and have fathers who participated in conscription for compulsory military training in 1969/70. Information on fathers' alcohol use was collected during conscription. Offspring was followed for suicide attempts or completed suicides (through linkage with national registers) from age 12 to end of follow-up in 2008.

RESULTS

After adjustment for confounders, the hazard ratio (HR) for offspring to fathers who were heavy drinkers was 1.4 (95% CI 1.02, 1.93) while the associations turned non-significant for offspring to fathers who often drank into intoxication, HR 1.14 (0.68, 1.90). The highest risk for suicidal behaviour was found for offspring to fathers who had been apprehended for drunkenness two times or more, or with an alcohol-related hospitalization, with adjusted HRs of 2.1 (1.4, 3,14) and 1.9 (1.27, 2,85) respectively.

CONCLUSION

Fathers' alcohol use is associated with increased risk of suicidal behaviour among offspring in youth and young adulthood.

Transgenerational influence of parental morphine exposure on pain perception, anxiety-like behavior and passive avoidance memory among male and female offspring of Wistar rats

Accumulating evidence suggests that epigenetic mechanisms play an important role in the formation and maintenance of memory within the brain. Moreover, the effect of parental drug-exposure before gestation on behavioral state of offspring has been little studied. The main objective of the current study is to evaluate the effect of parental morphine exposure on avoidance memory, morphine preference and anxiety-like behavior of offspring. The total of 32 males and 32 females were used for mating. The animals were treated with morphine. The offspring according to their parental morphine treatment was divided into four groups (n=16) including paternally treated, maternally treated, both of parents treated and naïve animals. The pain perception, anxiety-like behavior, and avoidance memory were evaluated in the offspring. In the current study, the total of 256 offspring was used for the experiments (4 tasks × 4 groups of offspring × 8 female offspring × 8 male offspring). The finding revealed that the avoidance memory and visceral pain were reduced significantly in male and female offspring with at least one morphine-treated parent. Moreover, anxiety-like behavior was reduced significantly in the male offspring with at least one morphine-treated parent. While anxiety-like behavior was increased significantly in female offspring that were treated by morphine either maternally or both of parents. The data revealed that the endogenous opioid system may be altered in the offspring of morphine-treated parent(s), and epigenetic role could be important. However, analysis of variance signified the important role of maternal inheritance.

From controlled to compulsive drug-taking: The role of the habenula in addiction

Addiction is now recognized as a neurobiological and cognitive brain disorder and is generally viewed as a switch from recreational or voluntary to compulsive substance use despite aversive consequences. The habenula, composed of medial (MHb) and lateral (LHb) domains, has been implicated in regulating behavioral flexibility and anxiety-related behaviors and is considered a core component of the brain "anti-reward" system. These functions position the habenula to influence voluntary behaviors. Consistent with this view, emerging evidence points to alterations in habenula activity as important factors to contributing the loss of control over the use of drugs of abuse and the emergence of compulsive drug seeking behaviors. In this review, we will discuss the general functions of the MHb and LHb and describe how these functional properties allow this brain region to promote or suppress volitional behaviors. Then, we highlight mechanisms by which drugs of abuse may alter habenular activity, precipitating the emergence of addiction-relevant behavioral abnormalities.

Translational Molecular Approaches in Substance Abuse Research

Excessive abuse of psychoactive substances is one of the leading contributors to morbidity and mortality worldwide. In this book chapter, we review translational research strategies that are applied in the pursuit of new and more effective therapeutics for substance use disorder (SUD). The complex, multidimensional nature of psychiatric disorders like SUD presents difficult challenges to investigators. While animal models are critical for outlining the mechanistic relationships between defined behaviors and genetic and/or molecular changes, the heterogeneous pathophysiology of brain diseases is uniquely human, necessitating the use of human studies and translational research schemes. Translational research describes a cross-species approach in which findings from human patient-based data can be used to guide molecular genetic investigations in preclinical animal models in order to delineate the mechanisms of reward circuitry changes in the addicted state. Results from animal studies can then inform clinical investigations toward the development of novel treatments for SUD. Here we describe the strategies that are used to identify and functionally validate genetic variants in the human genome which may contribute to increased risk for SUD, starting from early candidate gene approaches to more recent genome-wide association studies. We will next examine studies aimed at understanding how transcriptional and epigenetic dysregulation in SUD can persistently alter cellular function in the disease state. In our discussion, we then focus on examples from the literature illustrating molecular genetic methodologies that have been applied to studies of different substances of abuse - from alcohol and nicotine to stimulants and opioids - in order to exemplify how these approaches can both delineate the underlying molecular systems driving drug addiction and provide insights into the genetic basis of SUD.

Association between prodynorphin gene polymorphisms and opioid dependence susceptibility: a meta-analysis

BACKGROUND

Prodynorphin (PDYN) gene polymorphisms have been linked with opioid dependence (OD) with conflicting outcomes, the aim of this study is to synthesize the existing evidence of the association between PDYN polymorphisms and OD susceptibility.

METHODS

Four databases including PubMed, EMBASE, Web of Science, and Wanfang were retrieved for relevant studies before August, 2018. All identified studies were evaluated using predetermined inclusion and exclusion criteria. Summary odds ratio (OR) and 95% confidence interval (95%CI) were calculated to appraise the association. Statistical analysis was performed using RevMan 5.3 software.

RESULTS

A total of seven case-control studies with 3129 cases and 3289 controls were recruited in the meta-analysis. For rs910080, rs1997794, rs1022563, and rs2235749 polymorphisms of PDYN gene, there were six, four, five, and four studies eventually included, respectively. The findings indicated that rs910080 polymorphism was significantly correlated with OD among Asian population under allelic model (A vs. G, OR = 1.30, 95% CI 1.04-1.62, P = 0.02, FDR = 0.05) and dominant model (AA+AG vs. GG, OR = 1.25, 95% CI 1.04-1.51, P = 0.02, FDR = 0.05). However, rs1022563, rs1997794 and rs2235749 polymorphisms did not appear to associate with OD susceptibility.

CONCLUSIONS

There existed a significant association between rs1022563 polymorphism and OD among Asian population. As the included studies were not adequate to guarantee a robust and convincing conclusion, future studies with larger sample size among more ethnicities are recommended.

Shared and specific associations of substance use disorders on adverse outcomes: A national prospective study

BACKGROUND AND AIMS

Substance use disorders (SUD) frequently co-occur and are associated with numerous adverse outcomes and lower quality of life. The goal of this study was to examine whether the associations of SUD with adverse outcomes occur through a shared liability or are disorder-specific even after taking into account their frequent co-occurrence.

BASIC PROCEDURES

Data were drawn from the National Epidemiological Survey on Alcohol and Related Conditions. The association between nine SUDs assessed at Wave 1 (2001-2002) and a broad range of outcomes (divorce/separation, violence, unemployment, financial crisis, legal problems, problems with a neighbor, friend, or relative, and quality of life) at Wave 2 (2005-2005) were estimated separately and simultaneously using a latent variable model to account for their co-occurrence and identify potential disorder-specific effects.

MAIN FINDINGS

SUD at Wave 1 were associated with increased prevalence of all adverse outcomes at Wave 2 (p < .05). With the exception of nicotine dependence and tranquilizer use disorder, we found no specific associations of any SUD with any adverse outcome. Rather, associations occurred primarily through the latent variable representing the shared effects of the different SUDs.

CONCLUSIONS AND RELEVANCE

Our findings underscore the importance of adopting dimensional approaches to model the co-occurrence of SUD. Because SUD increases the risk of adverse outcomes mainly through a general predisposition representing mechanisms shared across SUD rather than through drug-specific mechanisms, this dimension should be considered as a therapeutic target to substantially advance prevention of adverse outcomes caused by SUD.

Mini Review: Socio-Cultural Influences on the Link Between ADHD and SUD

Attention-deficit/hyperactivity disorder (ADHD) is a risk factor for the development and persistence of substance use disorders (SUD). The prevalence of ADHD in patients with SUD varies across countries and cultures. So far, cross-cultural variance in ADHD prevalence rates among SUD patients was mainly ascribed to methodological differences between studies, leaving the role of societal and cultural practices in the ADHD-SUD link hardly acknowledged. The aim of the present mini review is to address this gap in the literature by providing evidence for the effect of socio-cultural practices on the ADHD-SUD link and suggesting directions for future research. To achieve this goal, we map the influence of socio-cultural factors on the ADHD-SUD link along three lines of research. The first line is concerned with the role of socio-cultural factors in the recognition, diagnosis and treatment of childhood ADHD. The second line of research is concerned with socio-cultural influences on substance use (e.g., religion, ethnic identity, acculturation, and socio-economic status). Finally, we describe potential socio-cultural factors which may operate as mechanisms for reducing or increasing access to substance abuse treatment (e.g., ethnic disparities in health care utilization). Identifying socio-cultural influences on the ADHD-SUD link may provide further insight into the bidirectional association between ADHD and SUD in different contexts and encourage future research in the field.

Genetics of cocaine and methamphetamine consumption and preference in Drosophila melanogaster

Illicit use of psychostimulants, such as cocaine and methamphetamine, constitutes a significant public health problem. Whereas neural mechanisms that mediate the effects of these drugs are well-characterized, genetic factors that account for individual variation in susceptibility to substance abuse and addiction remain largely unknown. Drosophila melanogaster can serve as a translational model for studies on substance abuse, since flies have a dopamine transporter that can bind cocaine and methamphetamine, and exposure to these compounds elicits effects similar to those observed in people, suggesting conserved evolutionary mechanisms underlying drug responses. Here, we used the D. melanogaster Genetic Reference Panel to investigate the genetic basis for variation in psychostimulant drug consumption, to determine whether similar or distinct genetic networks underlie variation in consumption of cocaine and methamphetamine, and to assess the extent of sexual dimorphism and effect of genetic context on variation in voluntary drug consumption. Quantification of natural genetic variation in voluntary consumption, preference, and change in consumption and preference over time for cocaine and methamphetamine uncovered significant genetic variation for all traits, including sex-, exposure- and drug-specific genetic variation. Genome wide association analyses identified both shared and drug-specific candidate genes, which could be integrated in genetic interaction networks. We assessed the effects of ubiquitous RNA interference (RNAi) on consumption behaviors for 34 candidate genes: all affected at least one behavior. Finally, we utilized RNAi knockdown in the nervous system to implicate dopaminergic neurons and the mushroom bodies as part of the neural circuitry underlying experience-dependent development of drug preference.

Illicit use of cocaine and methamphetamine is a major public health problem. Whereas the neurological effects of these drugs are well characterized, it remains challenging to determine genetic risk factors for substance abuse in human populations. The fruit fly, Drosophila melanogaster, presents an excellent model for identifying evolutionarily conserved genes that affect drug consumption, since genetic background and exposure can be controlled precisely. We took advantage of natural variation in a panel of inbred wild derived fly lines with complete genome sequences to assess the extent of genetic variation among these lines for voluntary consumption of cocaine and methamphetamine and to explore whether some genetic backgrounds might show experience-dependent development of drug preference. The drug consumption traits were highly variable among the lines with strong sex-, drug- and exposure time-specific components. We identified candidate genes and gene networks associated with variation in consumption of cocaine and methamphetamine and development of drug preference. Using tissue-specific suppression of gene expression, we were able to functionally implicate candidate genes that affected at least one consumption trait in at least one drug and sex. In humans, the mesolimbic dopaminergic projection plays a role in drug addiction. We asked whether in Drosophila the mushroom bodies could play an analogous role, as they are integrative brain centers associated with experience-dependent learning. Indeed, our results suggest that variation in consumption and development of preference for both cocaine and methamphetamine is mediated, at least in part, through a neural network that comprises dopaminergic projections to the mushroom bodies.

PCSK9 is Increased in Cerebrospinal Fluid of Individuals With Alcohol Use Disorder

BACKGROUND

Recent studies have shown that alcohol use affects the regulation and expression of proprotein convertase subtilisin/kexin 9 (PCSK9). While a major role of PCSK9 in hepatic function and lipid regulation has been clearly established, other pleiotropic effects remain poorly understood. Existing research suggests a positive association between PCSK9 expression in the brain and psychopathology, with increased levels of PCSK9 in the cerebrospinal fluid (CSF) of individuals with dementia and epigenetic modifications of PCSK9 associated with alcohol use disorder (AUD). In this study, we hypothesized that chronic alcohol use would increase PCSK9 expression in CSF.

METHODS

PCSK9 levels in CSF were measured in individuals with AUD (n = 42) admitted to an inpatient rehabilitation program and controls (n = 25). CSF samples in AUD were assessed at 2 time points, at day 5 and day 21 after admission. Furthermore, plasma samples were collected and measured from the individuals with AUD.

RESULTS

PCSK9 in CSF was significantly increased in the AUD group at day 5 and day 21 compared to the controls (p < 0.0001). Plasma PCSK9 levels were correlated positively with CSF PCSK9 levels in AUD (p = 0.0493).

CONCLUSIONS

Our data suggest that PCSK9 is elevated in the CSF of individuals with AUD, which may indicate a potential role of PCSK9 in AUD. Additional studies are necessary to further elucidate the functions of PCSK9 in the brain.

Alterations in resting-state functional connectivity in substance use disorders and treatment implications

Substance use disorders (SUD) are diseases of the brain, characterized by aberrant functioning in the neural circuitry of the brain. Resting state functional connectivity (rsFC) can illuminate these functional changes by measuring the temporal coherence of low-frequency fluctuations of the blood oxygenation level-dependent magnetic resonance imaging signal in contiguous or non-contiguous regions of the brain. Because this data is easy to obtain and analyze, and therefore fairly inexpensive, it holds promise for defining biological treatment targets in SUD, which could help maximize the efficacy of existing clinical interventions and develop new ones. In an effort to identify the most likely "treatment targets" obtainable with rsFC we summarize existing research in SUD focused on 1) the relationships between rsFC and functionality within important psychological domains which are believed to underlie relapse vulnerability 2) changes in rsFC from satiety to deprived or abstinent states 3) baseline rsFC correlates of treatment outcome and 4) changes in rsFC induced by treatment interventions which improve clinical outcomes and reduce relapse risk. Converging evidence indicates that likely "treatment target" candidates, emerging consistently in all four sections, are reduced connectivity within executive control network (ECN) and between ECN and salience network (SN). Other potential treatment targets also show promise, but the literature is sparse and more research is needed. Future research directions include data-driven prediction analyses and rsFC analyses with longitudinal datasets that incorporate time since last use into analysis to account for drug withdrawal. Once the most reliable biological markers are identified, they can be used for treatment matching, during preliminary testing of new pharmacological compounds to establish clinical potential ("target engagement") prior to carrying out costly clinical trials, and for generating hypotheses for medication repurposing.

The psychological and genetic factors of the addictive behaviors (PGA) study

OBJECTIVES

Most of the addiction studies focus on very specific aspects of addictions, often with contradictory results, and integrated studies are quite rare. Experimental studies comparing underlying mechanisms of addictions and analyzing data from an integrative psychological and genetic perspective are almost nonexistent. The aim of the present paper is to describe the research protocol of the Psychological and Genetic Factors of Addictive Behaviors (PGA) study, which applies an integrative approach to understanding the acquisition, development, and maintenance of addictive behaviors.

METHODS

A wide-spectrum national study was carried out. Data were collected from 3,003 adolescents. Addictions to both psychoactive substances and behaviors were thoroughly assessed via psychometrically robust scales, which also included assessment related to a wide range of related psychological dimensions. Additionally, a DNA sample was also collected from participants.

RESULTS

The paper presents the detailed methodology of the PGA study. Data collection procedures, instrumentation, and the analytical approach used to attain the research objectives are described.

CONCLUSIONS

Future plans, along with potential contributions of the PGA study, are also discussed. It is envisaged that the study will provide a unique opportunity to test possible mechanisms and causal pathways mediating the associations of genetic factors, psychological characteristics, and addictions.

Genetic influences on delayed reward discounting: A genome-wide prioritized subset approach

Delayed reward discounting (DRD) is a behavioral economic measure of impulsivity that has been consistently associated with addiction. It has also been identified as a promising addiction endophenotype, linking specific sources of genetic variation to individual risk. A challenge in the studies to date is that levels of DRD are often confounded with prior drug use, and previous studies have also had limited genomic scope. The current investigation sought to address these issues by studying DRD in healthy young adults with low levels of substance use (N = 986; 62% female, 100% European ancestry) and investigating genetic variation genome-wide. The genome-wide approach used a prioritized subset design, organizing the tests into theoretically and empirically informed categories and apportioning power accordingly. Three subsets were used: (a) a priori loci implicated by previous studies; (b) high-value addiction (HVA) markers from the recently developed SmokeScreen array; and (c) an atheoretical genome-wide scan. Among a priori loci, a nominally significant association was present between DRD and rs521674 in ADRA2A. No significant HVA loci were detected. One statistically significant genome-wide association was detected (rs13395777, p = 2.8 × 10-8), albeit in an intergenic region of unknown function. These findings are generally not supportive of the previous candidate gene studies and suggest that DRD has a complex genetic architecture that will require considerably larger samples to identify genetic associations more definitively. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Age of alcohol use initiation and psychiatric symptoms among young adult trauma survivors

Alcohol use disorder (AUD) evidences high rates of comorbidity with a range of psychiatric disorders, particularly within high-risk populations, such as individuals exposed to physical or sexual violence. Increasing efforts are focused on understanding the role of early alcohol use (e.g., during adolescence) on emotional and psychiatric functioning over time, as well as sex differences in these associations. The aim of the current study was to evaluate patterns of association between age of initiation of regular alcohol use and posttraumatic stress disorder (PTSD), anxiety, and depressive symptoms as a function of sex. Participants were 269 college students with a history of interpersonal trauma and alcohol use who completed a battery of questionnaires regarding alcohol use and emotional health. Neither bivariate correlations nor results from structural equation models covarying for key factors showed a relationship between age of alcohol use initiation and current psychiatric symptoms among men (n = 63). Results of a structural equation model supported an association between earlier age of alcohol use initiation and greater levels of current PTSD (β = -0.14), anxiety (β = -0.15), and depression symptoms (β = -0.16) in the female sub-sample (n = 202), after controlling for covariates, as well as intercorrelations among criterion variables. Statistical support for sex as a moderator of these associations was not detected. The current study provides preliminary evidence for potential sex differences in the role of early alcohol use in the development of psychiatric symptoms and highlights the need for systematic longitudinal research.

The spurious relationship between ecstasy use and neurocognitive deficits: A Bradford Hill review

Numerous studies have suggested that MDMA can cause neurocognitive deficits. However, the available data can only suggest an association - rather than a causal relationship - between MDMA use and neurocognitive deficits. The reliability and robustness of this association was evaluated using Bradford Hill's criteria for determining causation in epidemiology research. Several limitations in the literature were found. Studies have recruited people who abuse ecstasy - an illicit drug that does not always contain MDMA. There is inherent risk in consuming impure or falsely identified substances; and using this as a source as for scientific opinion may introduce biases in our understanding the actuals risks associated with MDMA. Importantly, given that ecstasy research is predominately retrospective, baseline functioning cannot be established; which may be influenced by a variety of preexisting factors. Many studies introduce statistical errors by inconsistently dichotomizing and comparing light and heavy ecstasy users, making dose-response relationships inconclusive. When interpreting the ecstasy literature effect sizes are a more meaningful indicator of neurocognitive functioning rather than relying on p-values alone. Most meta-analyses have failed to find clinically relevant differences between ecstasy users and controls. There is also consistent evidence of publication bias in this field of research, which indicates that the literature is both biased and incomplete. Finally, suggestions for improving the ecstasy literature are provided.

A Family Affair: Family Typologies of Problems and Midlife Well-Being

Background and Objectives

Midlife adults are a "pivot" generation, responding to parents' and grown children's problems. Yet, some midlife adults may have families where multiple members suffer sorrows, whereas other midlife adults may have families with few problems. This study examined: (a) typologies of problems across generations and (b) associations between profiles of problems and midlife adults' well-being.

Research Design and Methods

Midlife adults (N = 633) reported their own, each parent's (n = 868), and grown child's (n = 1,785) physical (e.g., injury, cancer), psychological (e.g., anxiety, addiction), and lifestyle problems (e.g., divorce, job loss), and parents' functional disabilities. Midlife adults reported their own depressive symptoms.

Results

Latent profile analysis revealed four family typologies: (a) lowest problems across generations (n = 364), (b) offspring and midlife adult moderate problems, parent high physical problems and disability (n = 165), (c) offspring and parent moderate problems (n = 90), and (d) offspring highest problems (n = 14). Midlife adults in the lowest problems group (Profile a) reported higher income and fewer depressive symptoms than midlife adults in the other groups.

Discussion and Implications

Midlife adults cope with challenges when grown children or parents suffer problems, and their well-being may suffer as a result. In this study, regardless of the profile, higher problems in either generation were associated with more depressive symptoms for midlife adults.

Severe acute alcoholic hepatitis and liver transplant: A never-ending mournful story

Severe acute alcoholic liver disease (SAAH) unresponsive to medical therapy shows one-year-mortality rates of up to 90%. Most transplant centers request six months of alcohol abstinence prior to transplantation, the so-called "6-month rule." This regulation is not based on strong evidence, repeatedly making it a topic of controversial debates. The majority of patients with SAAH will die before fulfilling the 6-month rule. Therefore, liver transplantation (LT) protocols are becoming more flexible towards the rigid abstinence regulation, especially concerning SAAH patients. We conducted a literature review regarding LT in SAAH and its outcomes, including post-transplant mortality and recidivism. We studied available data on PubMed from 2011 and onwards whilst including articles dealing with genetic components, medical therapy and historic snapshots of alcoholism. Emerging studies recommend LT in SAAH not responding to medical therapies even without realizing the required abstinence period, since the majority of these patients would die within 6 months. SAAH without response to medical therapy has one-year-mortality rates of up to 90%. The 6-month rule is not based on strong evidence and is repeatedly a topic of controversial debates. There is genetic linkage to alcoholism and medical therapy is not as effective as estimated, yet. The 6-months-regulation has not shown to evidently decrease the risk of recidivism post-LT, which is a lifesaving treatment in SAAH patients. Insisting on rigid sobriety rules results in excluding patients with a low risk of recidivism from being transplanted. Moreover, the genetic linkage of alcoholism must be recognized.

Transition to drug co-use among adolescent cannabis users: The role of decision-making and mental health

BACKGROUND

Co-use of cannabis and drugs other than cannabis (DOTC) influences the risk of experiencing cannabis disorders. Accordingly, we explored whether speed of transition to drug co-use, the number of DOTC used, and/or being an experimental cannabis-only user, a regular cannabis-only user, or a regular cannabis user who co-uses DOTC (i.e., cannabis-plus user) were associated with decision-making (DM), mental health disorder symptoms, or cannabis use-related characteristics.

METHODS

We analyzed baseline data from a sub-sample of 266 adolescent (ages 14 to 16) cannabis users (CU) participating in an ongoing longitudinal study. Assessments included semi-structured interviews, self-report questionnaires, and measures of drug use, DM (measured via the Iowa Gambling Task), mental health disorders, and cannabis use-related problems.

RESULTS

Endorsing a larger number of mood disorders symptoms was associated with being a regular cannabis-plus user rather than a regular cannabis-only user (AOR = 1.08, C.I.95% 1.01, 1.15). Poorer DM was associated with a faster transition to co-use, such that for each one unit increase in DM performance, the years to onset of drug co-use increased by 1% (p = 0.032). Endorsing a larger number of cannabis use-related problems was positively associated with endorsing a larger number of DOTC used (p = 0.001).

CONCLUSIONS

This study provides new evidence on the process of drug co-use among CU. Specifically, mood disorder symptoms were associated with use of DOTC among regular CU. Furthermore, poorer DM was associated with a faster transition to drug co-use. Poorer DM and mood disorder symptoms may aggravate or accelerate the onset of adverse consequences among adolescent CU.

Genetics of alcohol use disorder: a review

Alcohol use disorder (AUD) represents a significant and ongoing public health concern with 12-month prevalence estimates of ∼5.6%. Quantitative genetic studies suggest a heritability of approximately 50% for AUD, and as a result, significant efforts have been made to identify specific variation within the genome related to the etiology of AUD. Given the limited number of replicable findings that have emerged from genome-wide linkage and candidate gene association studies, more recent efforts have focused on the use of genome-wide association studies (GWAS). These studies have suggested that hundreds of variants across the genome, most of small effect (R² < 0.002), contribute to the genetic etiology of AUD. The present review describes the initial, though limited, successes of GWAS to identify loci related to risk for AUD as well as other etiologically relevant traits (e.g. alcohol consumption). In addition, 'Post-GWAS' approaches that rely on GWAS data to estimate the heritability and co-heritability of traits, test causal relations between traits, and aid in gene discovery are described. Together, the described research findings illustrate the importance of molecular genetic research on AUD as we seek to better understand the mechanisms through which genetic variation leads to increased risk for AUD.

NGF gene polymorphisms are not associated with heroin dependence in a Taiwanese male population

BACKGROUND AND OBJECTIVES

Heroin dependence (HD) is a chronic relapsing brain illness with substantial heritability. Nerve growth factor (NGF) is a crucial modulator in the neurodevelopment, and may be a key mediator of reward processes in HD. The purpose of this genetic study was to investigate whether NGF gene polymorphisms associate with the occurrence of HD and the specific personality traits of patients with HD.

METHODS

We selected a homogeneous Han Chinese male population to overcome possible confounding effects of population and gender. For the study, 272 HD patients and 141 controls completed the Tridimensional Personality Questionnaire to evaluate their personality traits. In addition, a further sample 303 HD patients and 204 controls was added (with totally 920 participants) for the gene association and genotype-phenotype interaction studies.

RESULTS

Patients with HD had higher novelty seeking (NS) and harm avoidance (HA) scores than healthy subjects. Nonetheless, NGF gene polymorphisms did not associate with specific personality traits in HD patients and controls. There is no significant difference in NGF gene polymorphisms between patients with HD and controls.

DISCUSSION AND CONCLUSIONS

The NGF gene may neither contribute to the risk of development of HD, nor mediate the relationship between specific personality traits and HD in Han Chinese male population.

SCIENTIFIC SIGNIFICANCE

Patients with HD had higher novelty seeking (NS) and harm avoidance (HA) scores than healthy subjects. However, none of the polymorphisms in the NGF gene affected the NS and HA scores in both patients and healthy subjects. (Am J Addict 2018;27:516-523).

Impact of exposure to alcohol marketing and subsequent drinking patterns among youth and young adults

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: To assess the impact of exposure to any form of alcohol marketing, compared to less exposure or no exposure, on alcohol consumption patterns among youth and young adults up to and including the age of 25 years (we want to be able to look at potential dose response relationships at different levels of exposure).

Blowing up money? The earnings penalty of smoking in the 1970s and the 21st century

We analyze the earnings penalty of smoking among Swedish twins in two social contexts: the 1970s, when smoking was common and widely accepted and when there were relatively few tobacco laws aiming to reduce smoking; and the 2000s, when smoking had become more expensive, stigmatizing and less common, and when tobacco laws and regulations had intensified. The results show that the short-term earnings penalty of smoking was much higher in the 21st century than in the 1970s for men. For women, smokers had on average higher annual earnings compared to nonsmokers in the 1970s, but lower annual earnings in the 2000s. In the long run, there was an earnings gap for men between never-smokers and continuous smokers, whereas there was a pronounced earnings 'bonus' of smoking cessation for women. The results emphasize the importance of social context and the long-term horizon when evaluating the consequences of smoking for earnings.

Genetic Association and Expression Analyses of the Phosphatidylinositol-4-Phosphate 5-Kinase (PIP5K1C) Gene in Alcohol Use Disorder-Relevance for Pain Signaling and Alcohol Use

BACKGROUND

The gene encoding phosphatidylinositol-4-phosphate 5-kinase (PIP5K1C) has been recently implicated in pain regulation. Interestingly, a recent cross-tissue and cross-phenotypic epigenetic analysis identified the same gene in alcohol use disorder (AUD). Given the high comorbidity between AUD and chronic pain, we hypothesized that genetic variation in PIP5K1C might contribute to susceptibility to AUD.

METHODS

We conducted a case-control association study of genetic variants in PIP5K1C. Association analyses of 16 common PIP5K1C single nucleotide polymorphisms (SNPs) were conducted in cases and controls of African (427 cases and 137 controls) and European ancestry (488 cases and 324 controls) using standard methods. In addition, given the prominent role of the opioid system in pain signaling, we investigated the effects of acute alcohol exposure on PIP5K1C expression in humanized transgenic mice for the μ-opioid receptor that included the OPRM1 A118G polymorphism, a widely used mouse model to study analgesic response to opioids in pain. PIP5K1C expression was measured in the thalamus and basolateral amygdala (BLA) in mice after short-term administration (single 2 g/kg dose) of alcohol or saline using immunohistochemistry and analyzed by 2-way analysis of variance.

RESULTS

In the case-control association study using an NIAAA discovery sample, 8 SNPs in PIP5K1C were significantly associated with AUD in the African ancestry (AA) group (p < 0.05 after correction; rs4807493, rs10405681, rs2074957, rs10432303, rs8109485, rs1476592, rs10419980, and rs4432372). However, a replication analysis using an independent sample (N = 3,801) found no significant associations after correction for multiple testing. In the humanized transgenic mouse model with the OPRM1 polymorphism, PIP5K1C expression was significantly different between alcohol and saline-treated mice, regardless of genotype, in both the thalamus (p < 0.05) and BLA (p < 0.01).

CONCLUSIONS

Our discovery sample shows that genetic variants in PIP5K1C are associated with AUD in the AA group, and acute alcohol exposure leads to up-regulation of PIP5K1C, potentially explaining a mechanism underlying the increased risk for chronic pain conditions in individuals with AUD.

Mechanisms of cortisol - Substance use development associations: Hypothesis generation through gene enrichment analysis

There are many theories about the mechanisms of associations between hypothalamic-pituitary-adrenal (HPA) function (indexed by cortisol) and substance use. However, the potential for genes that contribute to both HPA function and substance use to confound the association (e.g., genetic confounding) has largely been ignored. We explore the potential role of genetics in cortisol-substance use associations, build a conceptual framework placing theories and mechanisms for how cortisol and substance use are related into a developmental progression, and develop new hypotheses based on our findings. We conclude that the relationship between cortisol function and substance use is complex, occurs at multiple levels of analysis, and is bidirectional at multiple phases of the substance use progression. Additionally, there is potential for genetic confounding in cortisol-substance use associations, and thus a need for genetically informed designs to investigate how and why cortisol function is associated with substance use phenotypes from initiation through disorder. Gene-environment interplay and developmental context are likely to impact the effectiveness of prevention and intervention efforts to reduce substance use problems.

The Role of Cell Adhesion Molecule Genes Regulating Neuroplasticity in Addiction

A variety of genetic approaches, including twin studies, linkage studies, and candidate gene studies, has established a firm genetic basis for addiction. However, there has been difficulty identifying the precise genes that underlie addiction liability using these approaches. This situation became especially clear in genome-wide association studies (GWAS) of addiction. Moreover, the results of GWAS brought into clarity many of the shortcomings of those early genetic approaches. GWAS studies stripped away those preconceived notions, examining genes that would not previously have been considered in the study of addiction, consequently creating a shift in our understanding. Most importantly, those studies implicated a class of genes that had not previously been considered in the study of addiction genetics: cell adhesion molecules (CAMs). Considering the well-documented evidence supporting a role for various CAMs in synaptic plasticity, axonal growth, and regeneration, it is not surprising that allelic variation in CAM genes might also play a role in addiction liability. This review focuses on the role of various cell adhesion molecules in neuroplasticity that might contribute to addictive processes and emphasizes the importance of ongoing research on CAM genes that have been implicated in addiction by GWAS.

Filling the gap between lab and clinical impact: An open randomized diagnostic trial comparing urinary ethylglucuronide and ethanol in alcohol dependent outpatients

BACKGROUND

Efforts aimed at reducing alcohol-related harm include early detection of risky drinkers as well as detection of early relapse in patients with alcohol dependence. Ethyl glucuronide (EtG) has been proven to be a reliable biomarker for the detection of recent drinking; however, no randomized, diagnostic trial to date has tested its impact on drinking outcomes. The aim of this study was to assess, in a randomized design, the implications of EtG screening on alcohol outcomes, compared to screening with a low sensitivity biomarker such as ethanol.

METHODS

Alcohol dependent outpatients were randomized to either 24 weeks of continuous screening with EtG or ethanol. Patients were aware of screening methods and results. After 24 weeks, all participants were screened with EtG. Self-reports were also gathered. A logistic regression compared the rate of EtG positive results at study end between groups. Generalized estimating equations evaluated the descending monthly rate of EtG positive patients in the EtG group.

RESULTS

A total of 162 patients were randomized. During the study period, the ethanol group showed less patients with positive screens (19/64 (29.7%) vs 58/98 (59%)). After 24 weeks, the EtG group showed a greater number of patients having a negative screening test compared to ethanol subjects when they were all screened with EtG (5/62 (8.1%) vs 13/39 (33.3%)). A significant decrease in the rate of EtG positive patients was found for the first three months of the study.

CONCLUSIONS

Routine screening with EtG seems to reduce drinking and improve abstinence rates in alcohol dependent outpatients.

Independent associations and effect modification between lifetime substance use and recent mood disorder diagnosis with household food insecurity

Poor mental health and substance use are associated with food insecurity, however, their potential combined effects have not been studied. This study explored independent associations and effect modification between lifetime substance use and mood disorder in relation to food insecurity. Poisson regression analysis of data from British Columbia respondents (n = 13,450; 12 years+) in the 2007/08 Canadian Community Health Survey was conducted. Measures included The Household Food Security Survey Module (7.3% food insecure), recent diagnosis of a mood disorder (self-reported; 9.5%), lifetime use of cannabis, cocaine/crack, ecstasy, hallucinogens, and speed, any lifetime substance use, sociodemographic covariates, and the interaction terms of mood disorder by substance. For those with recent diagnosis of a mood disorder the prevalence of lifetime substance use ranged between 1.2 to 5.7% and were significantly higher than those without recent mood disorder diagnosis or lifetime use of substances (p’s < 0.05). For respondents with a recent mood disorder diagnosis or who used cannabis, food insecurity prevalence was higher compared to the general sample (p < 0.001); prevalence was lower for cocaine/crack use (p < 0.05). Significant effect modification was found between mood disorder with cannabis, ecstasy, hallucinogen and any substance use over the lifetime (PRs 0.51 to 0.64, p’s 0.022 to 0.001). Independent associations were found for cocaine/crack and speed use (PRs 1.68, p’s < 0.001) and mood disorder (PRs 2.02, p’s < 0.001). Based on these findings and the existing literature, future study about coping and resilience in the context of substance use, mental health, and food insecurity may lead to the development of relevant interventions aimed at mental well-being and food security.

Genetic analysis of impulsive personality traits: Examination of a priori candidates and genome-wide variation

Impulsive personality traits are heritable risk factors and putative endophenotypes for addiction and other psychiatric disorders involving disinhibition. This study examined the genetic basis of impulsive personality traits, defined as scores on the Barratt Impulsiveness Scale (BIS-11) and the UPPS-P Impulsive Behavior Scale (UPPS-P). In 983 healthy young adults of European ancestry, the study examined genetic variation in relation to a combined phenotype of seven subscales based on high phenotypic intercorrelations. The study first tested 14 a priori loci that have previously been associated impulsive personality traits or closely related constructs. Second, the study included an exploratory genome-wide scan (i.e., GWAS), acknowledging that only relatively large effects would be detectable in a sample size of ~ 1000. A priori SNP analyses revealed a significant association between the combined impulsivity phenotype and two SNPs within the 5-HT2a receptor gene (HTR2A; rs6313 and rs6311). Follow-up analyses suggested that the effects were specific to the Motor and Non-planning subscales on the BIS-11, and also that the two loci were in linkage disequilibrium. The GWAS yielded no statistically significant findings. This study further implicates loci within HTR2A with certain forms of self-reported impulsivity and identifies candidates for future investigation from the genome-wide analyses.

Opposite Epigenetic Associations With Alcohol Use and Exercise Intervention

Alcohol use disorder (AUD) is a devastating public health problem in which both genetic and environmental factors play a role. Growing evidence supports that epigenetic regulation is one major mechanism in neuroadaptation that contributes to development of AUD. Meanwhile, epigenetic patterns can be modified by various stimuli including exercise. Thus, it is an intriguing question whether exercise can lead to methylation changes that are opposite to those related to drinking. We herein conducted a comparative study to explore this issue. Three cohorts were profiled for DNA methylation (DNAm), including a longitudinal exercise intervention cohort (53 healthy participants profiled at baseline and after a 12-months exercise intervention), a cross-sectional case-control cohort (81 hazardous drinkers and 81 healthy controls matched in age and sex), and a cross-sectional binge drinking cohort (281 drinkers). We identified 906 methylation sites showing significant DNAm differences between drinkers and controls in the case-control cohort, as well as, associations with drinking behavior in the drinking cohort. In parallel, 341 sites were identified for significant DNAm alterations between baseline and follow-up in the exercise cohort. Thirty-two sites overlapped between these two set of findings, of which 15 sites showed opposite directions of DNAm associations between exercise and drinking. Annotated genes of these 15 sites were enriched in signaling pathways related to synaptic plasticity. In addition, the identified methylation sites significantly associated with impaired control over drinking, suggesting relevance to neural function. Collectively, the current findings provide preliminary evidence that exercise has the potential to partially reverse DNAm differences associated with drinking at some CpG sites, motivating rigorously designed longitudinal studies to better characterize epigenetic effects with respect to prevention and intervention of AUD.

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

The primary aim of this study was to investigate the genetic predisposition of Internet gaming disorder (IGD), and the secondary aim was to compare the results to those of alcohol dependence (AD). Two independent case-control studies were conducted. A total of 30 male participants with IGD, diagnosed according to the 5^th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria, and 30 sex-matched controls participated in study 1. We designed targeted exome sequencing (TES) to test for 72 candidate genes that have been implicated in the pathogenesis of addiction. The genes included seven neurotransmitter (dopamine, serotonin, glutamate, r-aminobutyric acid (GABA), norepinephrine, acetylcholine, and opioid) system genes. A total of 31 male in-patients with AD and 29 normal male controls (NC) were enrolled in study 2. The same 72 genes included in study 1 and ten additional genes related to alcohol-metabolic enzyme were selected as the target genes, and we identified the genetic variants using the same method (TES). The IGD group had a lower frequency of the T allele of rs1044396 in the nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4), and this variant represents a protective allele against IGD. However, we did not find a significant difference in the polymorphisms of the 72 genes that encode neurotransmitter systems between the AD and NC groups. This study demonstrated that rs1044396 of CHRNA4 was significantly associated with IGD.

Perceived parental alcohol problems and drinking patterns in youth: A cross-sectional study of 69,030 secondary education students in Denmark

The aim of the study was to examine whether young people with parental alcohol problems have different drinking patterns than those without parental alcohol problems. Further, we examined whether the association between parental alcohol problems and young people's drinking patterns differed depending on the gender of the child and the parent, and whether more severe parental alcohol problems and cohabitation with the parent with alcohol problems was associated with earlier and heavier drinking patterns. Data came from the Danish National Youth Study 2014, a web-based national survey. 75,025 high school and vocational school students (15-25years) participated. Drinking patterns were investigated by the following outcomes: non-drinking, weekly alcohol consumption, frequent binge drinking, and early intoxication debut age. The main predictor variables were perceived parental alcohol problems, gender of the parent with alcohol problems, cohabitation with a parent with alcohol problems and severity of the parents' alcohol problems. Young people with parental alcohol problems had a higher weekly alcohol consumption (boys: 15.2 vs. 13.9 drinks per week; girls: 11.6 vs. 10.2 drinks per week), higher odds of early intoxication debut age (boys: OR=1.68 [95% CI 1.50-1.89]; girls: OR 1.95 [95% CI 1.79-2.14]), and more frequent binge drinking (boys, OR=1.16 [95% CI 1.04-1.29]; girls, OR=1.21 [95% CI 1.11-1.32]) compared to young people without parental alcohol problems. In conclusion, this study shows that young people with perceived parental alcohol problems have an earlier intoxication debut age, binge drink more frequently, and drink larger quantities per week than young people without perceived parental alcohol problems.

Age of Drinking Initiation as a Risk Factor for Alcohol Use Disorder Symptoms is Moderated by ALDH2*2 and Ethnicity

BACKGROUND

An early age of drinking initiation (ADI) has been associated with increased risk for alcohol use disorders (AUDs), but the consistency of this risk across diverse samples has not been well studied. The purpose of this study was to examine whether the pathway from ADI to AUD symptoms by early adulthood is moderated by ethnicity and possessing an alcohol-metabolizing gene ALDH2*2 variant allele.

METHODS

We used multigroup structural equation modeling, including 5 groups split by ethnicity and ALDH2*2, to examine the consistency of the path from ADI to AUD symptoms in 604 Chinese-, Korean-, and White-American college students. We further examined the effects of ALDH2*2, ethnicity, and their interaction in Asians to better understand their unique contributions to the moderation.

RESULTS

The association between ADI and AUD symptoms was moderated, with ADI negatively associated with AUD symptoms among Koreans without ALDH2*2 and Whites, but not among Koreans with ALDH2*2 or Chinese regardless of ALDH2*2. Both ALDH2*2 and ethnicity within Asians contributed unique variability in the effect.

CONCLUSIONS

Ethnicity and ALDH2*2 altered the relationship of ADI as a risk factor for AUD symptoms. Being Chinese and possessing an ALDH2*2 allele within Koreans both buffered against the risk for AUD symptoms associated with earlier ADI, indicating that this relationship can be attenuated by protective factors.

The association of prenatal cocaine exposure, externalizing behavior and adolescent substance use

Prenatal cocaine exposure (PCE) may increase adolescent substance use through alterations of neurotransmitter systems affecting fetal brain development. The relationship between PCE and substance use at 15 and 17 years was examined. Subjects (365: 186 PCE; 179 non-cocaine exposed (NCE)) supplied biologic and self-report data using the Youth Risk Behavior Surveillance System (YRBSS) and Computerized Diagnostic Interview Schedule for Children (C-DISC 4) at ages 15 and 17. The relationship between PCE and substance use was assessed using General Estimating Equation (GEE) analyses controlling for confounding factors including violence exposure and preschool lead level. Teens with PCE vs. NCE teens were 2 times more likely to use tobacco (OR=2.1; 95% CI 1.21-3.63; p<.001) and marijuana (OR=1.85; CI 1.18-2.91; p<.001) and have a substance use disorder at age 17 (OR=2.51; CI 1.00-6.28; p<.05). Evaluation of PCE status by gender revealed an association between PCE and marijuana use that was more pronounced for boys than girls at 17 years. Violence exposure was also a significant predictor of alcohol (p<.001), tobacco (p<.05), and marijuana (p<.0006) use and substance abuse/dependence (p<.01). Externalizing behavior at age 12 fully mediated the effects of PCE on substance use disorder at age 17 and partially mediated effects of PCE on tobacco use, but did not mediate effects on marijuana use. The percentage of substance use reported increased between 15 and 17 years, with no differences between the PCE and NCE groups. Data suggest specialized drug use prevention measures for children with PCE may benefit this high risk group.

Alcohol use disorder and GABAB receptor gene polymorphisms in an Italian sample: haplotype frequencies, linkage disequilibrium and association studies

BACKGROUND

Alcohol use disorder (AUD) is a complex trait with genetic and environmental influences. Several gene variants have been associated with the risk for AUD, including genes encoding the sub-units of the γ-aminobutyric acid (GABA) receptors.

AIM

This study evaluated whether specific single nucleotide polymorphisms (SNPs) in genes encoding GABAB receptor sub-units can be considered as candidates for the risk of AUD.

SUBJECTS AND METHODS

Seventy-four AUD subjects and 128 Italian controls were genotyped for 10 SNPs in genes encoding GABA-B1 and GABA-B2 sub-units (GABBR1 and GABBR2). Allele, genotype, and haplotype frequencies were tested for the association with the AUD trait.

RESULTS

A significant difference between AUD individuals and controls was observed at genotype level for rs2900512 of GABBR2 gene. The homozygous T/T genotype was not found in the controls, whereas it was over-represented in the AUD individuals. Under the recessive model (T/T vs C/T + C/C) this result was statistically significant, as well as the Odds Ratio for the association with the AUD trait.

CONCLUSIONS

The results provide preliminary data on the association between GABAB receptor gene variation and risk of AUD. To confirm this finding, studies with larger samples and additional characterisation of the phenotypic AUD trait are required.

The relationship between initial route of heroin administration and speed of transition to daily heroin use

INTRODUCTION AND AIMS

The effect of heroin administration route on speed of transition to regular use is unknown. This paper aims to determine whether the speed of transition from initiation of heroin use to daily heroin use differs by route of administration (injecting, chasing/inhaling or snorting).

DESIGN AND METHODS

Privileged access interviewer survey of purposively selected sample of 395 current people who use heroin (both in and not in treatment) in London, UK (historical sample from 1991). Data on age and year of initiation, time from initiation to daily use and routes of administration were collected by means of a structured questionnaire. Generalised ordered logistic models were used to test the relationship between route of initial administration of heroin and speed of transition to daily heroin use. Analyses were adjusted for gender, ethnicity, daily use of other drug(s) at time of initiation, year of initiation and treatment status at interview.

RESULTS

After adjustment, participants whose initial administration route was injecting had a 4.71 (95% confidence interval 1.34-16.5) increase in likelihood of progressing to daily use within 1-3 weeks of initiation, compared to those whose initial administration route was non-injecting.

DISCUSSION AND CONCLUSIONS

The speed of transition from first use to daily heroin use is faster if the individual injects heroin at initiation of use. Those who initiate heroin use through injecting have a shorter time frame for intervention before drug use escalation. [Hines LA, Lynskey M, Morley KI, Griffiths P, Gossop M, Powis B, Strang J. The relationship between initial route of heroin administration and speed of transition to daily heroin use. Drug Alcohol Rev 2017;00:000-000].

Alcohol effects on the epigenome in the germline: Role in the inheritance of alcohol-related pathology

Excessive alcohol exposure has severe health consequences, and clinical and animal studies have demonstrated that disruptions in the epigenome of somatic cells, such as those in brain, are an important factor in the development of alcohol-related pathologies, such as alcohol-use disorders (AUDs) and fetal alcohol spectrum disorders (FASDs). It is also well known that alcohol-related health problems are passed down across generations in human populations, but the complete mechanisms for this phenomenon are currently unknown. Recent studies in animal models have suggested that epigenetic factors are also responsible for the transmission of alcohol-related pathologies across generations. Alcohol exposure has been shown to induce changes in the epigenome of sperm of exposed male animals, and these epimutations are inherited in the offspring. This paper reviews evidence for multigenerational and transgenerational epigenetic inheritance of alcohol-related pathology through the germline. We also review the literature on the epigenetic effects of alcohol exposure on somatic cells in brain, and its contribution to AUDs and FASDs. We note gaps in knowledge in this field, such as the lack of clinical studies in human populations and the lack of data on epigenetic inheritance via the female germline, and we suggest future research directions.

Recreational concentrations of alcohol enhance synaptic inhibition of cerebellar unipolar brush cells via pre- and postsynaptic mechanisms

Variation in cerebellar sensitivity to alcohol/ethanol (EtOH) is a heritable trait associated with alcohol use disorder in humans and high EtOH consumption in rodents, but the underlying mechanisms are poorly understood. A recently identified cellular substrate of cerebellar sensitivity to EtOH, the GABAergic system of cerebellar granule cells (GCs), shows divergent responses to EtOH paralleling EtOH consumption and motor impairment phenotype. Although GCs are the dominant afferent integrator in the cerebellum, such integration is shared by unipolar brush cells (UBCs) in vestibulocerebellar lobes. UBCs receive both GABAergic and glycinergic inhibition, both of which may mediate diverse neurological effects of EtOH. Therefore, the impact of recreational concentrations of EtOH (~10-50 mM) on GABA_A receptor (GABA_AR)- and glycine receptor (GlyR)-mediated spontaneous inhibitory postsynaptic currents (sIPSCs) of UBCs in cerebellar slices was characterized. Sprague-Dawley rat (SDR) UBCs exhibited sIPSCs mediated by GABA_ARs, GlyRs, or both, and EtOH dose-dependently (10, 26, 52 mM) increased their frequency and amplitude. EtOH increased the frequency of glycinergic and GABAergic sIPSCs and selectively enhanced the amplitude of glycinergic sIPSCs. This GlyR-specific enhancement of sIPSC amplitude resulted from EtOH actions at presynaptic Golgi cells and via protein kinase C-dependent direct actions on postsynaptic GlyRs. The magnitude of EtOH-induced increases in UBC sIPSC activity varied across SDRs and two lines of mice, in parallel with their respective alcohol consumption/motor impairment phenotypes. These data indicate that Golgi cell-to-UBC inhibitory synapses are targets of EtOH, which acts at pre- and postsynaptic sites, via Golgi cell excitation and direct GlyR enhancement.NEW & NOTEWORTHY Genetic variability in cerebellar alcohol/ethanol sensitivity (ethanol-induced ataxia) predicts ethanol consumption phenotype in rodents and humans, but the cellular and molecular mechanisms underlying genetic differences are largely unknown. Here it is demonstrated that recreational concentrations of alcohol (10-30 mM) enhance glycinergic and GABAergic inhibition of unipolar brush cells through increases in glycine/GABA release and postsynaptic enhancement of glycine receptor-mediated responses. Ethanol effects varied across rodent genotypes parallel to ethanol consumption and motor sensitivity phenotype.

SNP by SNP by environment interaction network of alcoholism

Background

Alcoholism has a strong genetic component. Twin studies have demonstrated the heritability of a large proportion of phenotypic variance of alcoholism ranging from 50–80%. The search for genetic variants associated with this complex behavior has epitomized sequence-based studies for nearly a decade. The limited success of genome-wide association studies (GWAS), possibly precipitated by the polygenic nature of complex traits and behaviors, however, has demonstrated the need for novel, multivariate models capable of quantitatively capturing interactions between a host of genetic variants and their association with non-genetic factors. In this regard, capturing the network of SNP by SNP or SNP by environment interactions has recently gained much interest.

Results

Here, we assessed 3,776 individuals to construct a network capable of detecting and quantifying the interactions within and between plausible genetic and environmental factors of alcoholism. In this regard, we propose the use of first-order dependence tree of maximum weight as a potential statistical learning technique to delineate the pattern of dependencies underpinning such a complex trait. Using a predictive based analysis, we further rank the genes, demographic factors, biological pathways, and the interactions represented by our SNP \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \times $$\end{document}×SNP\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \times $$\end{document}×E network. The proposed framework is quite general and can be potentially applied to the study of other complex traits. 

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-017-0403-7) contains supplementary material, which is available to authorized users.

Genetic Counseling for Alcohol Addiction: Assessing Perceptions and Potential Utility in Individuals with Lived Experience and Their Family Members

Though addictions to substances including alcohol are highly heritable, there have been no studies regarding the possible applicability of genetic counseling to this set of conditions. Adults (≥18 years old) with a personal and/or family history of alcohol addiction were recruited to participate in an online survey-based study comprising 43 questions about beliefs/concern about recurrence risk and etiology of alcohol addiction and its impact on childbearing decisions, and perceptions of potential utility of genetic counseling for alcohol addiction. We applied primarily descriptive statistics, but also tested the hypotheses that perceiving genetic counseling to be useful would be associated with: 1) increasing importance attributed to genetics in the etiology of alcohol addiction, and 2) greater concern about recurrence of alcohol addiction (in self and/or children). Overall, the 113 participants recognized the multifactorial nature of alcohol addiction but reported a wide range of estimated recurrence risks for first-degree relatives. Overall, 62% perceived genetic counseling for alcohol addiction to be potentially beneficial. Participants were more likely to perceive a benefit from genetic counseling if they were concerned about recurrence for themselves (p = .021) or perceived genetics to be etiologically important in alcohol addiction (p = .024). Future studies are warranted to evaluate the outcomes of genetic counseling for addictions with respect to patient understanding, lifestyle modifications and psychological adaptation.