The genetic epidemiology of substance use disorder: A review

Disentangling heterogeneity in substance use disorder: Insights from genome-wide polygenic scores

Substance use disorder (SUD) is a global health problem with a significant impact on individuals and society. The presentation of SUD is diverse, involving various substances, ages at onset, comorbid conditions, and disease trajectories. Current treatments for SUD struggle to address this heterogeneity, resulting in high relapse rates. SUD often co-occurs with other psychiatric and mental health-related conditions that contribute to the heterogeneity of the disorder and predispose to adverse disease trajectories. Family and genetic studies highlight the role of genetic and environmental factors in the course of SUD, and point to a shared genetic liability between SUDs and comorbid psychopathology. In this study, we aimed to disentangle SUD heterogeneity using a deeply phenotyped SUD cohort and polygenic scores (PGSs) for psychiatric disorders and related traits. We explored associations between PGSs and various SUD-related phenotypes, as well as PGS-environment interactions using information on lifetime emotional, physical, and/or sexual abuse. Our results identify clusters of individuals who exhibit differences in their phenotypic profile and reveal different patterns of associations between SUD-related phenotypes and the genetic liability for mental health-related traits, which may help explain part of the heterogeneity observed in SUD. In our SUD sample, we found associations linking the genetic liability for attention-deficit hyperactivity disorder (ADHD) with lower educational attainment, the genetic liability for post-traumatic stress disorder (PTSD) with higher rates of unemployment, the genetic liability for educational attainment with lower rates of criminal records and unemployment, and the genetic liability for well-being with lower rates of outpatient treatments and fewer problems related to family and social relationships. We also found evidence of PGS-environment interactions showing that genetic liability for suicide attempts worsened the psychiatric status in SUD individuals with a history of emotional physical and/or sexual abuse. Collectively, these data contribute to a better understanding of the role of genetic liability for mental health-related conditions and adverse life experiences in SUD heterogeneity.

Circadian rhythmicity in schizophrenia male patients with and without substance use disorder comorbidity

Circadian rhythmicity is associated to clinical variables that play an important role in both schizophrenia (SZ) and substance use disorders (SUD), although the characteristics of the coexistence of these two diagnoses (SZ +) remain mostly unknown. Hence, we studied a sample of 165 male patients divided in three groups each of 55, according to their diagnoses (SZ + , SZ, and SUD), as well as a healthy control (HC; n = 90) group. Alongside with sociodemographic and clinical variables, circadian rhythms were registered through a sleep-wake data structured interview, a circadian typology questionnaire, and distal skin temperature (DST) using the Thermochron iButton every 2 min during 48 h. Analyses showed that SZ + and SZ patients presented a longer sleep (delay in wake-up time) and mostly an intermediate circadian typology, while SUD patients slept less hours, displaying a morning typology. The DST showed the highest daily activation and stability for the SUD group, even when compared with the HC group. The presence of schizophrenia (SZ + and SZ) was related to a DST pattern with a reduced amplitude determined by a wakefulness impairment, which was more pronounced for SZ patients whose sleep period was adequate. The assessment of circadian rhythms in under treatment male patients with SZ should be focused on the diurnal period as a possible marker of either treatment adherence or patient's recovery, irrespective of the presence of a comorbid SUD. Further research with additional objective measures may provide knowledge transferable to therapeutic strategies and could be useful to establish possible endophenotypes in the future.

Interactions Between Genetic, Prenatal Substance Use, Puberty, and Parenting are Less Important for Understanding Adolescents' Internalizing, Externalizing, and Substance Use than Developmental Cascades in Multifactorial Models

This study tested interactions among puberty-related genetic risk, prenatal substance use, harsh discipline, and pubertal timing for the severity and directionality (i.e., differentiation) of externalizing and internalizing problems and adolescent substance use. This is a companion paper to Marceau et al. (2021) which examined the same influences in developmental cascade models. Data were from the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort (n = 4504 White boys, n = 4287 White girls assessed from the prenatal period through 18.5 years). We hypothesized generally that later predictors would strengthen the influence of puberty-related genetic risk, prenatal substance use exposure, and pubertal risk on psychopathology and substance use (two-way interactions), and that later predictors would strengthen the interactions of earlier influences on psychopathology and substance use (three-way interactions). Interactions were sparse. Although all fourteen interactions showed that later influences can exacerbate or trigger the effects of earlier ones, they often were not in the expected direction. The most robust moderator was parental discipline, and differing and synergistic effects of biological and socially-relevant aspects of puberty were found. In all, the influences examined here operate more robustly in developmental cascades than in interaction with each other for the development of psychopathology and transitions to substance use.

Examining interactions between polygenic scores and interpersonal trauma exposure on alcohol consumption and use disorder in an ancestrally diverse college cohort

Introduction: Genetic factors impact alcohol consumption and use disorder (AUD), with large-scale genome-wide association studies (GWAS) identifying numerous associated variants. Aggregate genetic methods in combination with important environmental factors (e.g., interpersonal trauma [IPT]) can be applied to expand our understanding of the ways by which genetic and environmental variables work together to influence alcohol consumption and disordered use. The present study aimed to detail the relationships between genome-wide polygenic scores (PGS) for alcohol phenotypes (i.e., alcohol consumption and AUD status) and IPT exposure as well as the interaction between them across ancestry. Methods: Data were drawn from the Spit for Science (S4S) study, a US college student population, where participants reported on IPT exposure prior to college and alcohol consumption and problems during college (N = 9,006; ancestry: 21.3% African [AFR], 12.5% Admixed Americas [AMR], 9.6% East Asian [EAS], 48.1% European [EUR], 8.6% South Asian [SAS]). Two trans-ancestry PGS were constructed, one for alcohol consumption and another for AUD, using large-scale GWAS summary statistics from multiple ancestries weighted using PRS-CSx. Regression models were applied to test for the presence of associations between alcohol-PGS and IPT main and interaction effects. Results: In the meta-analysis across ancestry groups, IPT exposure and PGS were significantly associated with alcohol consumption (βIPT = 0.31, P IPT = 0.0002; βPGS = 0.09, P PGS = 0.004) and AUD (ORIPT = 1.12, P IPT = 3.5 × 10-8; ORPGS = 1.02, P PGS = 0.002). No statistically significant interactions were detected between IPT and sex nor between IPT and PGS. When inspecting ancestry specific results, the alcohol consumption-PGS and AUD-PGS were only statistically significant in the EUR ancestry group (βPGS = 0.09, P PGS = 0.04; ORPGS = 1.02, P PGS = 0.022, respectively). Discussion: IPT exposure prior to college was strongly associated with alcohol outcomes in this college-age sample, which could be used as a preventative measure to identify students at high risk for problematic alcohol use. Additionally, results add to developing evidence of polygenic score association in meta-analyzed samples, highlighting the importance of continued efforts to increase ancestral representation in genetic studies and inclusive analytic approaches to increase the generalizability of results from genetic association studies.

Substance Use Disorder

Substance use disorders (SUDs) present a challenge in the emergency department (ED) setting. This article provides an overview of SUDs, their clinical assessment, legal considerations in drug testing, diagnosis, and treatment approaches. SUDs are prevalent and coexist with mental health disorders, necessitating comprehensive evaluation and management. Clinical assessment involves screening tools, substance use history, and identification of comorbidities. Diagnosis relies on a thorough evaluation of substance abuse patterns and associated medical conditions. Treatment approaches encompass a multidisciplinary approach, incorporating counseling, medications, and social support. Effective management of SUDs in the ED requires a comprehensive understanding of these complex disorders.

An approach for prioritizing candidate genes from RNA-seq using preclinical cocaine self-administration datasets as a test case

RNA-sequencing (RNA-seq) technology has led to a surge of neuroscience research using animal models to probe the complex molecular mechanisms underlying brain function and behavior, including substance use disorders. However, findings from rodent studies often fail to be translated into clinical treatments. Here, we developed a novel pipeline for narrowing candidate genes from preclinical studies by translational potential and demonstrated its utility in 2 RNA-seq studies of rodent self-administration. This pipeline uses evolutionary conservation and preferential expression of genes across brain tissues to prioritize candidate genes, increasing the translational utility of RNA-seq in model organisms. Initially, we demonstrate the utility of our prioritization pipeline using an uncorrected P-value. However, we found no differentially expressed genes in either dataset after correcting for multiple testing with false discovery rate (FDR < 0.05 or <0.1). This is likely due to low statistical power that is common across rodent behavioral studies, and, therefore, we additionally illustrate the use of our pipeline on a third dataset with differentially expressed genes corrected for multiple testing (FDR < 0.05). We also advocate for improved RNA-seq data collection, statistical testing, and metadata reporting that will bolster the field's ability to identify reliable candidate genes and improve the translational value of bioinformatics in rodent research.

Substance Use Disorders in Women

Substance use disorder (SUD) is among the leading causes of premature morbidity and mortality and imposes significant health, economic, and social burdens. Gender differences have been found in the development, course, and treatment of SUD, with women at increased risk for physiologic and psychosocial consequences compared with men. Reasons for these differences are multifold and include biological, genetic, environmental, and behavioral factors. This article discusses SUD among women, emphasizing clinical considerations for care. Specific topics include epidemiology, sex and gender differences, common comorbidities, screening, diagnosis, treatment, pregnancy, and sociocultural factors.

Genetic factors linked to aberrant neural activity of individuals with substance use disorder phenotypes: A systematic review and meta-analysis of EEG studies

Background: Alterations in EEG activity have been considered valid endophenotypes of substance use disorders (SUDs). Empirical evidence has supported the association between genetic factors (e.g., genes, single nucleotide polymorphisms [SNPs]) and SUDs, considering both clinical samples and individuals with a positive family history of SUDs [F⁺SUD]). Nevertheless, the relationship between genetic factors and intermediate phenotypes (i.e., altered EEG activity) among individuals with SUD phenotypes remains unclear.Objective(s): The current study aims at summarizing genetic factors linked to aberrant EEG activity among individuals with SUDs and those with F⁺SUD.Methods: Sixteen studies (5 [N = 986] + 11 from the Collaborative Studies On Genetics of Alcoholism [COGA] sample [432 ≤ N ≤ 8810]) were included for a qualitative systematic review. Thirteen studies (5 + 8 studies from the COGA sample) were used for multi-level meta-analytic procedures.Results: Qualitative analyses highlighted a multivariate genetic architecture linked to alterations in EEG waves among individuals with SUD phenotypes (i.e., augmented resting-state beta waves; reduced resting-state alpha waves; reduced resting-state and task-dependent theta waves). The most recurrent genetic factors were involved in cellular energy homeostasis, modulation of inhibitory and excitatory neural activity together with neural cell growth. Meta-analytic results showed a moderate association between genetic factors and altered resting-state and task-dependent EEG activity. Meta-analytic results also suggested non-additive genetic effects on altered EEG activity.Conclusions: Complex genetic interactions mediating neural activity and brain development might constitute a causal pathway toward intermediate phenotypes associated with phenotypic features, which in turn are linked to SUDs.

The Role of Environment, Early Use, Genetic Influences, and Neurobiology in Substance Use Disorder

Substance use disorders (SUDs) have dire consequences for the individual, family, and community. Although SUDs were once viewed as a moral issue, they are now understood to be complex, chronic brain illnesses associated with both genetic and non-genetic influences. The American Psychiatric Association recognizes SUDs associated with the use of 10 different substances, for example, alcohol, nicotine, opioids, cannabis, caffeine, hallucinogens, inhalants, sedatives, hypnotics, and stimulants. Environmental exposure to substances, early use, genetic influences, and neurobiology have all been correlated with an increased likelihood of the development of SUDs. Having a broader understanding of these complex disorders is key for prevention.

Modulation of Gut Microbiome in Ecstasy/MDMA-Induced Behavioral and Biochemical Impairment in Rats and Potential of Post-Treatment with Anacyclus pyrethrum L. Aqueous Extract to Mitigate Adverse Effects

The use of illicit substances continues to pose a substantial threat to global health, affecting millions of individuals annually. Evidence suggests the existence of a 'brain-gut axis' as the involving connection between the central nervous system and gut microbiome (GM). Dysbiosis of the GM has been associated with the pathogenesis of various chronic diseases, including metabolic, malignant, and inflammatory conditions. However, little is currently known about the involvement of this axis in modulating the GM in response to psychoactive substances. In this study, we investigated the effect of MDMA (3,4-methylenedioxymethamphetamine, "Ecstasy")-dependence on the behavioral and biochemical responses, and the diversity and abundance of the gut microbiome in rats post-treated (or not) with aqueous extract of Anacyclus pyrethrum (AEAP), which has been reported to exhibit anticonvulsant activity. The dependency was validated using the conditioned place preference (CPP) paradigm, behavioral, and biochemical tests, while the gut microbiota was identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The CPP and behavioral tests confirmed the presence of MDMA withdrawal syndrome. Interestingly, treatment with AEAP led to a compositional shift in the GM compared to the MDMA-treated rats. Specifically, the AEAP group yielded a higher relative abundance of Lactobacillus and Bifidobacter, while animals receiving MDMA had higher levels of E. coli. These findings suggest that A. pyrethrum therapy may directly modulate the gut microbiome, highlighting a potential target for regulating and treating substance use disorders.

Thiol disulfide homeostasis in psychiatric disorders: A comprehensive review

Thiol-disulfide couple maintains an intracellular redox status. Dynamic thiol-disulfide homeostasis acts crucial parts in metabolic processes involving signal mechanisms, inflammation, antioxidant defense. Thiol-disulfide homeostasis have been implicated in numerous diseases. In this comprehensive review we identified the studies that examined the thiol-disulfide homeostasis in psychiatric disorders. Most cases demonstrated alterations in thiol-disulfide homeostasis and in most of them the thiol-disulfide balance tended to change direction to the disulfide side, that is, to the oxidative side. Currently, the fact that N-acetylcysteine, a thiol-containing compound, is of great interest as a new treatment approach in psychiatric disorders and the role of glutathione, the most abundant thiol, in the brain highlights the importance of evaluating the thiol-disulfide balance in psychiatric disorders.

Factors related to the development of executive functions: A cumulative dopamine genetic score and environmental factors predict performance of kindergarten children in a go/nogo task

BACKGROUND

This study aimed at investigating the interaction between genetic and environmental factors in predicting executive function in children aged four to six years.

METHODS

Response inhibition as index of EF was assessed in 197 children using a go/nogo task. A cumulative dopamine (DA) genetic score was calculated, indexing predisposition of low DA activity. Dimensions of parenting behavior and parental education were assessed.

RESULTS

Parental education was positively related to accuracy in nogo trials. An interaction between the cumulative genetic score and the parenting dimension Responsiveness predicted go RT indicating that children with a high cumulative genetic score and high parental responsiveness exhibited a careful response mode.

CONCLUSION

The development of EF in kindergarten children is related to parental education as well as to an interaction between the molecular-genetics of the DA system and parenting behavior.

Examining common and distinct contributions to the etiology of suicide attempt and reattempt

This study examined the extent to which the genetic and environmental characteristics of having a first versus a second suicide attempt (SA) are common or specific. We evaluated the direct pathway between these phenotypes and the role of specific risk factors. From Swedish national registries, two subsamples of individuals born between 1960 and 1980 were selected (1,227,287 twin-sibling pairs and 2,265,796 unrelated individuals). First, a twin-sibling model was fit to evaluate the genetic and environmental risk factors related to first and second SA. The model also included a direct path between first and second SA. Second, an extended Cox proportional hazards model (PWP) was used to evaluate the risk factors related to first versus second SA. In the twin-sibling model, suicide reattempt was strongly related to first SA (β = 0.72). The total heritability for the second SA was estimated at 0.48, with 45.80% unique to this second SA. The total environmental influence for the second SA was 0.51, with 50.59% unique. In the PWP model, we found that childhood environment, psychiatric disorders, and selected stressful life events were related to both first and second SA, potentially reflecting common genetic and environmental factors. Other stressful life events were associated with first but not second SA in the multivariable model, suggesting their specificity in explaining the first occurrence of SA but not its recurrence. Specific risk factors related to second SA need to be further explored. These findings have important implications for describing the pathways toward suicidal behavior and identifying individuals at risk for multiple SA. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Behavioral phenotypes revealed during reversal learning are linked with novel genetic loci in diversity outbred mice

Impulsive behavior and impulsivity are heritable phenotypes that are strongly associated with risk for substance use disorders. Identifying the neurogenetic mechanisms that influence impulsivity may also reveal novel biological insights into addiction vulnerability. Our past studies using the BXD and Collaborative Cross (CC) recombinant inbred mouse panels have revealed that behavioral indicators of impulsivity measured in a reversal-learning task are heritable and are genetically correlated with aspects of intravenous cocaine self-administration. Genome-wide linkage studies in the BXD panel revealed a quantitative trait locus (QTL) on chromosome 10, but we expect to identify additional QTL by testing in a population with more genetic diversity. To this end, we turned to Diversity Outbred (DO) mice; 392 DO mice (156 males, 236 females) were phenotyped using the same reversal learning test utilized previously. Our primary indicator of impulsive responding, a measure that isolates the relative difficulty mice have with reaching performance criteria under reversal conditions, revealed a genome-wide significant QTL on chromosome 7 (max LOD score = 8.73, genome-wide corrected p<0.05). A measure of premature responding akin to that implemented in the 5-choice serial reaction time task yielded a suggestive QTL on chromosome 17 (max LOD score = 9.14, genome-wide corrected <0.1). Candidate genes were prioritized (2900076A07Rik, Wdr73 and Zscan2) based upon expression QTL data we collected in DO and CC mice and analyses using publicly available gene expression and phenotype databases. These findings may advance understanding of the genetics that drive impulsive behavior and enhance risk for substance use disorders.

Signal in the noise: Altered brain activation among adolescent alcohol users detected via the analysis of intra-individual variability1

RATIONALE

Unlike its average level, the variability in brain activation over time or trials can capture subtle and brief disruptions likely to occur among participants with low-to-moderate levels of substance use or misuse.

OBJECTIVE

The present study used this intra-individual variability measurement approach to detect neural processing differences associated with light-to-moderate use of alcohol among 14-19-year-old adolescents.

METHOD

A total of 128 participants reporting any level of alcohol use during the previous 6 months and 87 participants reporting no use during this period completed intake questionnaires and interviews as well as an assessment of P300 electroencephalographic responses to novel stimuli recorded during two separate tasks.

RESULTS

In addition to differing in recent alcohol use, the groups differed in nicotine and cannabis use, risk-taking behavior and conduct disorder symptoms, and P300 amplitude inter-trial variability (ITV) across both tasks. Across all participants, P300 ITV was positively correlated with a family history of depression but not with a family history of alcohol dependence. There were no group differences in P300 amplitude averaged across trials.

CONCLUSIONS

Recent reports attributing brain volume or brain function differences to an effect of light-to-moderate alcohol use should be viewed with great caution. In the present analysis of brain function differences among substance-using adolescents, the group differences were small, complicated by many factors coinciding with or preceding alcohol use, and not reflected in a stable central tendency.

Substance use and substance use disorders in Africa: An epidemiological approach to the review of existing literature

The relationship between man and substances that have abuse potentials, and whose use has been associated with the development or progression of substance use disorders has continued to evolve in terms of geography, economic implications, and time. History shows that local plants with psychoactive constituents can get exported worldwide through global travel, commerce, or even conquest. Time and globalization also change people’s relationship with substances of abuse; hence, an area that was initially alien to certain substances might evolve to becoming a trafficking hub, and then a destination. A case in point is Africa where a rapidly increasing prevalence of substance use/abuse and substance use disorder among adolescents and young adults is putting enormous strain on the economy, healthcare system, and society at large. However, there appears to be a paucity of scientific literature and data on the epidemiology, risk assessment, and contributing factors to substance use and the development of substance use disorders across Africa. In this narrative review, we examine extant literature (PubMed, Google scholar, Medline) for information on the prevalence, trends, and influencers of substance use and the development of substance use disorders. This is with a view of understanding the determinants of substance use and factors that influence the development of substance use disorders in the region, and how this information can be channeled towards developing a comprehensive intervention and treatment program.

Opioid Use Disorder: Treatment Outcomes in U.S. Veterans

BACKGROUND

Substance use disorders are a leading cause of morbidity and mortality in the United States, with opioid use disorder representing a growing public health concern and economic burden. Veterans within the Veterans Health Administration are impacted by opioid use disorder.

SIGNIFICANCE

A common medication-assisted treatment is sublingual Suboxone (buprenorphine/naloxone) used in combination with behavior modification therapy. Missed Suboxone doses may lead to withdrawal and potential drug diversion. Sublocade (buprenorphine extended-release) is an alternative once-monthly subcutaneous injection administered by a healthcare provider. The purpose of this quality improvement project was to examine the effects of Sublocade on cravings in veterans with opioid use disorder.

METHODS

Veterans were considered for Sublocade monthly injections if they were enrolled in the Suboxone program, not taking Suboxone as prescribed, and disenrolled from the Suboxone program more than 2 times. Cravings were measured before and after Sublocade program enrollment.

RESULTS

Fifteen veterans were enrolled in the Sublocade program over a 12-month timeframe. Most were male (93%) with a median (range) age of 42 (33-62) years. The following were the primary opioids used before enrollment in the substance use disorder program: hydrocodone (47%), oxycodone (20%), and heroin (20%). Sublocade significantly reduced cravings (p = .001). In this small group, cravings were fully eliminated.

DISCUSSION

Recent studies have shown Sublocade effectively blocks the effects of other opioids and minimizes the risk of medication diversion that occurs with Suboxone. For these reasons, Sublocade is an alternative medication-assisted treatment for veterans with opioid use disorder.

Midazolam, methamphetamine, morphine and nicotine intake in high‐drinking‐in‐the‐dark mice

The high-drinking-in-the-dark (HDID) lines of mice were selectively bred for achieving high blood alcohol levels in the drinking-in-the-dark (DID) task and have served as a unique genetic risk model for binge-like alcohol intake. However, little is known about their willingness to consume other addictive drugs. Here, we examined (a) whether the HDID-1 and HDID-2 lines of mice would voluntarily consume midazolam, methamphetamine, morphine and nicotine in a DID test and (b) whether the HDID lines differ from their founders, heterogeneous stock/Northport (HS/NPT), in consumption levels of these drugs at the concentrations tested. Separate groups of HDID-1, HDID-2 and HS/NPT mice were given 4 days of access to each drug, using the single-bottle, limited-access DID paradigm. Male and female mice of both HDID lines consumed all four offered drugs. We observed no genotype differences in 40 μg/ml methamphetamine intake, but significant differences in nicotine, midazolam and morphine intake. Both HDID lines drank significantly more (150 μg/ml) midazolam than their founders, providing strong support for a shared genetic contribution to binge ethanol and midazolam intake. HDID-2 mice, but not HDID-1 mice, consumed more morphine (700 μg/ml) and more nicotine across a range of concentrations than HS/NPT mice. These results demonstrate that the HDID mice can be utilized for tests of voluntary drug consumption other than ethanol and highlight potentially important differences between HDID lines in risk for elevated drug intake.

Examining protective factors for substance use problems and self-harm behavior during adolescence: A longitudinal co-twin control study

Sports participation, physical activity, and friendship quality are theorized to have protective effects on the developmental emergence of substance use and self-harm behavior in adolescence, but existing research has been mixed. This ambiguity could reflect, in part, the potential for confounding of observed associations by genetic and environmental factors, which previous research has been unable to rigorously rule out. We used data from the prospective, population-based Child and Adolescent Twin Study in Sweden (n = 18,234 born 1994-2001) and applied a co-twin control design to account for potential genetic and environmental confounding of sports participation, physical activity, and friendship quality (assessed at age 15) as presumed protective factors for adolescent substance use and self-harm behavior (assessed at age 18). While confidence intervals widened to include the null in numerous co-twin control analyses adjusting for childhood psychopathology, parent-reported sports participation and twin-reported positive friendship quality were associated with increased odds of alcohol problems and nicotine use. However, parent-reported sports participation, twin-reported physical activity, and twin-reported friendship quality were associated with decreased odds of self-harm behavior. The findings provide a more nuanced understanding of the risks and benefits of putative protective factors for risky behaviors that emerge during adolescence.

Association of Polymorphism within the Putative miRNA Target Site in the 3'UTR Region of the DRD2 Gene with Neuroticism in Patients with Substance Use Disorder

The study aims at looking into associations between the polymorphism rs6276 that occurs in the putative miRNA target site in the 3'UTR region of the DRD2 gene in patients with substance use disorder (SUD) comorbid with a maniacal syndrome (SUD MANIA). In our study, we did not state any essential difference in DRD2 rs6276 genotype frequencies in the studied samples of SUD MANIA, SUD, and control subjects. A significant result was found for the SUD MANIA group vs. SUD vs. controls on the Neuroticism Scale of NEO FFI test, and DRD2 rs6276 (p = 0.0320) accounted for 1.7% of the variance. The G/G homozygous variants were linked with lower results on the neuroticism scale in the SUD MANIA group because G/G alleles may serve a protective role in the expression of neuroticism in patients with SUD MANIA. So far, there have been no data in the literature on the relationship between the miRSNP rs6276 region in the DRD2 gene and neuroticism (personal traits) in patients with a diagnosis of substance use disorder comorbid with the affective, maniacal type disturbances related to SUD. This is the first report on this topic.

Risk of pain disorders in offspring of parents with substance use disorders

AIMS

Individuals with substance use disorders (SUD) have higher risk of developing pain disorders. This study aimed to investigate the risk of major psychiatric disorders (MPD), SUD, and pain disorders among their offspring.

METHODS

This study used data from the Taiwan National Health Research Database. The case cohort included participants who had a parent diagnosed with SUD. The matched control cohort was offspring of parents without any SUD or major psychiatric disorder (MPD). Poisson regression was applied to estimate the risk of MPD, SUD, and pain disorder between case and control cohorts.

RESULTS

We recruited 13,840 cases and 138,400 matched controls. After adjusting for demographic characteristics and family history of psychiatric disorder, the offspring of parents with SUD had higher risk for bipolar disorder (reported as risk ratio with 95% confidence interval: 2.48, 1.79-3.43), depressive disorder (2.22, 1.94-2.52), SUD (2.53, 2.18-2.92), and alcohol use disorder (1.43, 1.16-1.76) than controls. With adjustments of demographic characteristics, individual MPD, and family history of psychiatric disorder, they also presented higher risk than controls for several pain disorders, including migraine (1.43, 1.15-1.78), fibromyalgia (1.21, 1.03-1.42), dorsopathies (1.20, 1.06-1.37), dysmenorrhea (1.16, 1.04-1.29), irritable bowel syndrome (1.26, 1.11-1.43), and dyspepsia (1.14, 1.02-1.27).

CONCLUSIONS

Clinicians should be aware of the influence of parental SUD on the elevated risk for MPD, SUD, and pain disorders in their offspring.

ADHD co-morbidities: A review of implication of gene × environment effects with dopamine-related genes

ADHD is a major burden in adulthood, where co-morbid conditions such as depression, substance use disorder and obesity often dominate the clinical picture. ADHD has substantial shared heritability with other mental disorders, contributing to comorbidity. However, environmental risk factors exist but their interaction with genetic makeup, especially in relation to comorbid disorders, remains elusive. This review for the first time summarizes present knowledge on gene x environment (GxE) interactions regarding the dopamine system. Hitherto, mainly candidate (GxE) studies were performed, focusing on the genes DRD4, DAT1 and MAOA. Some evidence suggest that the variable number tandem repeats in DRD4 and MAOA may mediate GxE interactions in ADHD generally, and comorbid conditions specifically. Nevertheless, even for these genes, common variants are bound to suggest risk only in the context of gender and specific environments. For other polymorphisms, evidence is contradictory and less convincing. Particularly lacking are longitudinal studies testing the interaction of well-defined environmental with polygenic risk scores reflecting the dopamine system in its entirety.

Efficacy of Health Beliefs Model-Based Intervention in Changing Substance Use Beliefs among Mosul University Students: A Randomized Controlled Trial

Substance use disorders (SUD) are a significant health concern worldwide. Substance abuse is a persistent problem linked to high rates of illness and loss. These issues are also responsible for many healthcare workers and health bills. However, the Substance use problems are associated with capitalize health retrogradation, weakness and death due to impacts and exceed. Throughout Iraq, there is growing concern about the effects of violence and war on drug use. To see how effective HBM-based intervention is at changing college students' health beliefs about drug usage. Using a randomized controlled trial approach, experimental design is carried out throughout the current study to determine the efficacy of health beliefs model-based intervention in changing the belief related to substance use among university students in Mosul City from 26-November 2019 to 1-March 2021. The study sample consisted of 80 students who participated in the training program for behavioral change. The intervention for the experimental group involved a health education lecture about substance use. Analyzed data using SPSS, Version 23 using both descriptive statistics and inferential statistics (Means, SD, Number and percentage). These results revealed statistically significant differences among all concepts of the Health Belief Model related to substance use, adding to behavioral motivation, behavioral control and intention) overtime. On the contrary, the perceived barrier was the only belief that showed no significant changes over time. According to the findings, the design of an HBM-based study could impact students' cognition and conduct in the field of drug dependence. Given the positive association across HBM dimensions and pupils' opinions, notably in "significant advantages and regarded harshness," These beliefs seemed to have a strong connection to each other and the avoidance of alcoholism. Keywords: Efficacy, Health Beliefs Model, Belief, Substance Use, Students.

Child Maltreatment and Substance Use: A Behavior Genetic Analysis

Child maltreatment is a pervasive social problem often perpetuated by family members and is related to a wide array of negative life outcomes. Although substance use is an outcome commonly associated with experiences of child maltreatment, not all individuals who experience maltreatment struggle with such issues. Many individuals can positively adapt to experiences of maltreatment based on levels of resilience and susceptibility. Research suggests that genetic differences may partly explain why negative outcomes develop for some, but not for others. Few studies have examined the extent to which genetic and environmental factors influence the longitudinal association between child maltreatment and varying forms of substance use, leaving a fundamental gap in our current understanding of this association. The current study aims to address this gap by analyzing a sample of twins from the National Longitudinal Study of Adolescent to Adult Health (Add Health). Findings from a series of univariate and bivariate biometric models reveal that the longitudinal associations between maltreatment, cigarette use, and marijuana use are accounted for by additive genetic and nonshared environmental factors. Moreover, the magnitude of the contribution varies across unique subgroups of cigarette and marijuana use. Directions for future research and theoretical implications are discussed.

A review of mathematical modeling of addiction regarding both (neuro-) psychological processes and the social contagion perspectives

Addiction is a complex biopsychosocial phenomenon, impacted by biological predispositions, psychological processes, and the social environment. Using mathematical and computational models that allow for surrogative reasoning may be a promising avenue for gaining a deeper understanding of this complex behavior. This paper reviews and classifies a selection of formal models of addiction focusing on the intra- and inter-individual dynamics, i.e., (neuro) psychological models and social models. We find that these modeling approaches to addiction are too disjoint and argue that in order to unravel the complexities of biopsychosocial processes of addiction, models should integrate intra- and inter-individual factors.

Familial co-aggregation and shared heritability between depression, anxiety, obesity and substance use

Depression, anxiety, obesity and substance use are heritable and often co-occur. However, the mechanisms underlying this co-occurrence are not fully understood. We estimated their familial aggregation and co-aggregation as well as heritabilities and genetic correlations to improve etiological understanding. Data came from the multi-generational population-based Lifelines Cohort Study (n = 162,439). Current depression and anxiety were determined using the MINI International Neuropsychiatric Interview. Smoking, alcohol and drug use were assessed by self-report questionnaires. Body mass index (BMI) and obesity were calculated by measured height and weight. Modified Cox proportional hazards models estimated recurrence risk ratios (λ_R), and restricted maximum likelihood variance decomposition methods estimated heritabilities (h²) and genetic correlations (r_G). All analyses were adjusted for age, age², and sex. Depression, anxiety, obesity and substance use aggregated within families (λ_{R first-degree relative} = 1.08-2.74) as well as between spouses (λ_R = 1.11-6.60). All phenotypes were moderately heritable (from h²_depression = 0.25 to h²_BMI = 0.53). Depression, anxiety, obesity and smoking showed positive familial co-aggregation. That is, each of these traits confers increased risk on the other ones within families, consistent with the positive genetic correlations between these phenotypes (r_G = 0.16-0.94). The exception was obesity, which showed a negative co-aggregation with alcohol and drug use and vice versa, consistent with the negative genetic correlations of BMI with alcohol (r_G = -0.14) and soft drug use (r_G = -0.10). Patterns of cross-phenotype recurrence risk highlight the co-occurrence among depression, anxiety, obesity and substance use within families. Patterns of genetic overlap between these phenotypes provide clues to uncovering the mechanisms underlying familial co-aggregation.

Ankk1 Loss of Function Disrupts Dopaminergic Pathways in Zebrafish

Ankyrin repeat and kinase domain containing 1 (ANKK1) is a member of the receptor-interacting protein serine/threonine kinase family, known to be involved in cell proliferation, differentiation and activation of transcription factors. Genetic variation within the ANKK1 locus is suggested to play a role in vulnerability to addictions. However, ANKK1 mechanism of action is still poorly understood. It has been suggested that ANKK1 may affect the development and/or functioning of dopaminergic pathways. To test this hypothesis, we generated a CRISPR-Cas9 loss of function ankk1 zebrafish line causing a 27 bp insertion that disrupts the ankk1 sequence introducing an early stop codon. We found that ankk1 transcript levels were significantly lower in ankk1 mutant (ankk127ins) fish compared to their wild type (ankk1+/+) siblings. In ankk1+/+ adult zebrafish brain, ankk1 protein was detected in isocortex, hippocampus, basolateral amygdala, mesencephalon, and cerebellum, resembling the mammalian distribution pattern. In contrast, ankk1 protein was reduced in the brain of ankk127ins/27ins fish. Quantitative polymerase chain reaction analysis revealed an increase in expression of drd2b mRNA in ankk127ins at both larval and adult stages. In ankk1+/+ adult zebrafish brain, drd2 protein was detected in cerebral cortex, cerebellum, hippocampus, and caudate homolog regions, resembling the pattern in humans. In contrast, drd2 expression was reduced in cortical regions of ankk127ins/27ins being predominantly found in the hindbrain. No differences in the number of cell bodies or axonal projections detected by anti-tyrosine hydroxylase immunostaining on 3 days post fertilization (dpf) larvae were found. Behavioral analysis revealed altered sensitivity to effects of both amisulpride and apomorphine on locomotion and startle habituation, consistent with a broad loss of both pre and post synaptic receptors. Ankk127ins mutants showed reduced sensitivity to the effect of the selective dopamine receptor antagonist amisulpride on locomotor responses to acoustic startle and were differentially sensitive to the effects of the non-selective dopamine agonist apomorphine on both locomotion and habituation. Taken together, our findings strengthen the hypothesis of a functional relationship between ANKK1 and DRD2, supporting a role for ANKK1 in the maintenance and/or functioning of dopaminergic pathways. Further work is needed to disentangle ANKK1’s role at different developmental stages.

Substance Use among Youth in Community and Residential Mental Health Care Facilities in Ontario, Canada

There is a need to improve the integration of substance use and mental health care for children and youth. This study examines risk and protective factors for substance use among youth with mental health conditions who received community-based or residential care services between 2012–2020 in Ontario, Canada. In this study, a cross-sectional design was used to examine patterns and factors associated with substance use among youth (12–18 years) assessed in the community (n = 47,418) and residential (n = 700) mental health care facilities in Ontario, Canada. Youth were assessed with the interRAI Child and Youth Mental Health Assessment (ChYMH). Substance use is identified by any substance use (including alcohol) 14 to 30 days prior to assessment. Logistic regression with generalized estimating equations was used to examine clinical, psychosocial, and environmental factors associated with substance use. This study shows that 22.3% of youth reported the use of substances in the community settings and 37% in residential settings. Older age group (Youth older than 16 years), being a victim of abuse, having experienced self-injurious ideation/attempt, being at risk of disrupted education, and having a parent/caregiver with addiction or substance use disorder were significantly associated with substance use. Several factors reduced the risk of substance use, including being a female, having anxiety symptoms, and having cognition problems. In conclusion, the study found that individual and parental factors increase youth’s risk of substance use, highlighting the importance of a holistic approach that includes consideration of social and biological risk factors to prevention/risk reduction, risk assessment, management, and recovery.

Methylation quantitative locus rs3758653 in the DRD4 gene is associated with duration from first heroin exposure to addiction

Opioid addiction is a chronic brain disease with a high heritability. However, the genetic underpinnings remain uncertain. DNA methylation is involved in the adaptive changes in neuroplasticity after prolonged drug use. The dopamine receptor D4 (DRD4) has an essential role in the reward processes associated with addictive drugs. To further elucidate the potential role and mechanism of the DRD4 gene variants in heroin addiction, we detected the methylation level of 46 CpG sites in the promoter region and the genotypes of three SNPs in the DRD4 gene. Correlations between the SNPs and methylation levels of the CpG sites, i.e., the analysis of methylation quantitative trait loci (mQTLs) was conducted. Following the identification of mQTLs that are unique in the heroin addiction group, we performed an association study between the mQTLs and traits of heroin addiction. Our results revealed that there were several correlations of SNPs rs3758653 and rs11246226 with the methylation levels of some CpG sites in the DRD4 gene. Among these SNP-CpG pairs, rs3758653-DRD4_04, rs3758653-DRD4_05, rs3758653-DRD4_13 and rs3758653-DRD4_03 were unique in the heroin addiction group. Moreover, we found that mQTL rs3758653 was associated with duration from first heroin exposure to addiction, and the expression level of the DRD4 gene in human brain regions of the frontal cortex and hippocampus. Our findings suggested that some mQTLs in the genome may be associated with traits of opioid addiction through implicating the processes of DNA methylation and gene expression.

Pharmacogenetics of Addiction Therapy

Drug addiction is a serious relapsing disease that has high costs to society and to the individual addicts. Treatment of these addictions is still in its nascency, with only a few examples of successful therapies. Therapeutic response depends upon genetic, biological, social, and environmental components. A role for genetic makeup in the response to treatment has been shown for several addiction pharmacotherapies with response to treatment based on individual genetic makeup. In this chapter, we will discuss the role of genetics in pharmacotherapies, specifically for cocaine, alcohol, and opioid dependences. The continued elucidation of the role of genetics should aid in the development of new treatments and increase the efficacy of existing treatments.

Lower-Risk Cannabis Use Guidelines (LRCUG) for reducing health harms from non-medical cannabis use: A comprehensive evidence and recommendations update

BACKGROUND

Cannabis use is common, especially among young people, and is associated with risks for various health harms. Some jurisdictions have recently moved to legalization/regulation pursuing public health goals. Evidence-based 'Lower Risk Cannabis Use Guidelines' (LRCUG) and recommendations were previously developed to reduce modifiable risk factors of cannabis-related adverse health outcomes; related evidence has evolved substantially since. We aimed to review new scientific evidence and to develop comprehensively up-to-date LRCUG, including their recommendations, on this evidence basis.

METHODS

Targeted searches for literature (since 2016) on main risk factors for cannabis-related adverse health outcomes modifiable by the user-individual were conducted. Topical areas were informed by previous LRCUG content and expanded upon current evidence. Searches preferentially focused on systematic reviews, supplemented by key individual studies. The review results were evidence-graded, topically organized and narratively summarized; recommendations were developed through an iterative scientific expert consensus development process.

RESULTS

A substantial body of modifiable risk factors for cannabis use-related health harms were identified with varying evidence quality. Twelve substantive recommendation clusters and three precautionary statements were developed. In general, current evidence suggests that individuals can substantially reduce their risk for adverse health outcomes if they delay the onset of cannabis use until after adolescence, avoid the use of high-potency (THC) cannabis products and high-frequency/-intensity of use, and refrain from smoking-routes for administration. While young people are particularly vulnerable to cannabis-related harms, other sub-groups (e.g., pregnant women, drivers, older adults, those with co-morbidities) are advised to exercise particular caution with use-related risks. Legal/regulated cannabis products should be used where possible.

CONCLUSIONS

Cannabis use can result in adverse health outcomes, mostly among sub-groups with higher-risk use. Reducing the risk factors identified can help to reduce health harms from use. The LRCUG offer one targeted intervention component within a comprehensive public health approach for cannabis use. They require effective audience-tailoring and dissemination, regular updating as new evidence become available, and should be evaluated for their impact.

Interactions between genetic, prenatal, cortisol, and parenting influences on adolescent substance use and frequency: A TRAILS study

INTRODUCTION

Dynamic relations between genetic, hormone, and pre- and postnatal environments are theorized as critically important for adolescent substance use but are rarely tested in multifactorial models. This study assessed the impact of interactions of genetic risk and cortisol reactivity with prenatal and parenting influences on both any and frequency of adolescent substance use.

METHODS

Data are from the TRacking Adolescents' Individual Lives Survey (TRAILS), a prospective longitudinal, multi-rater study of 2,230 Dutch adolescents. Genetic risk was assessed via 3 substance-specific polygenic scores. Mothers retrospectively reported prenatal risk when adolescents were 11 years old. Adolescents rated their parents' warmth and hostility at age 11. Salivary cortisol reactivity was measured in response to a social stress task at age 16. Adolescents' self-reported cigarette, alcohol, and cannabis use frequency at age 16.

RESULTS

A multivariate hurdle regression model showed that polygenic risk for smoking, alcohol, and cannabis predicted any use of each substance, respectively, but predicted more frequent use only for smoking. Blunted cortisol reactivity predicted any use and more frequent use for all 3 outcomes. There were 2 interactions: blunted cortisol reactivity exacerbated the association of polygenic risk with any smoking and the association of prenatal risk with any alcohol use.

CONCLUSION

Polygenic risk seems of importance for early use but less so for frequency of use, whereas blunted cortisol reactivity was correlated with both. Blunted cortisol reactivity may also catalyze early risks for substance use, though to a limited degree. Gene-environment interactions play no role in the context of this multifactorial model.

A population-wide perspective on the reach of substance use disorders: Parental exposure, diagnostic remission, and current disorders

BACKGROUND AND OBJECTIVES

Parental substance use disorder (SUD) increases the risk for childhood adversities. Lifetime and current SUDs are associated with functional impairment and psychiatric comorbidity. Research shows that these abate with diagnostic remission. However, a hierarchically ordered heuristic profile of adult subpopulations affected by SUDs has not been explored.

METHODS

We used data from the National Epidemiologic Survey on Alcohol and Related Conditions Wave III (NESARC-III; N = 36,309) to compare four subpopulations defined by the following hierarchy: (1) neither parental nor lifetime SUD (un-affected group); (2) parental SUD but no personal SUD; (3) past but not current SUD (diagnostic remission); and (4) current SUD. We conducted bivariate comparisons and multivariable-adjusted logistic regression to identify characteristics independently differentiating each group.

RESULTS

Almost half of the US adult population (108.9 million) were at risk from SUDs. Relative to the unaffected group (56.1%), the parental-exposure-only group (13.9%) experienced diverse parental and childhood adversities and increased risk for psychiatric disorders. Compared to the parental-exposure-only group those in the remitted group (14.1%) were more likely to report behavioral problems and lifetime psychiatric multimorbidities. Those with current SUD (15.9%) had a poorer mental health-related quality of life.

DISCUSSION AND CONCLUSIONS

This heuristic SUD hierarchy is associated with increasing adversities affecting almost half the US population, although only 15.9% meet the criteria for a current disorder.

SCIENTIFIC SIGNIFICANCE

Our findings provide a rigorous population-based estimate of the staggering public health impact of SUDs in the United States and suggest that almost half of the US population is either directly or indirectly affected by SUDs.

Genomic and Personalized Medicine Approaches for Substance Use Disorders (SUDs) Looking at Genome-Wide Association Studies

Drug addiction, or substance use disorder (SUD), is a chronic, relapsing disorder in which compulsive drug-seeking and drug-taking behaviour persist despite serious negative consequences. Drug abuse represents a problem that deserves great attention from a social point of view, and focuses on the importance of genetic studies to help in understanding the genetic basis of addiction and its medical treatment. Despite the complexity of drug addiction disorders, and the high number of environmental variables playing a role in the onset, recurrence, and duration of the symptoms, several studies have highlighted the non-negligible role of genetics, as demonstrated by heritability and genome-wide association studies. A correlation between the relative risk of addiction to specific substances and heritability has been recently observed, suggesting that neurobiological mechanisms may be, at least in part, inherited. All these observations point towards a scenario where the core neurobiological factors of addiction, involving the reward system, impulsivity, compulsivity, stress, and anxiety response, are transmitted, and therefore, genes and mutations underlying their variation might be detected. In the last few years, the development of new and more efficient sequencing technologies has paved the way for large-scale studies in searching for genetic and epigenetic factors affecting drug addiction disorders and their treatments. These studies have been crucial to pinpoint single nucleotide polymorphisms (SNPs) in genes that affect the reaction to medical treatments. This is critically important to identify pharmacogenomic approaches for substance use disorder, such as OPRM1 SNPs and methadone required doses for maintenance treatment (MMT). Nevertheless, despite the promising results obtained by genome-wide association and pharmacogenomic studies, specific studies related to population genetics diversity are lacking, undermining the overall applicability of the preliminary findings, and thus potentially affecting the portability and the accuracy of the genetic studies. In this review, focusing on cannabis, cocaine and heroin use, we report the state-of-the-art genomics and pharmacogenomics of SUDs, and the possible future perspectives related to medical treatment response in people that ask for assistance in solving drug-related problems.

Drinking and smoking polygenic risk is associated with childhood and early-adulthood psychiatric and behavioral traits independently of substance use and psychiatric genetic risk

Alcohol drinking and tobacco smoking are hazardous behaviors associated with a wide range of adverse health outcomes. In this study, we explored the association of polygenic risk scores (PRS) related to drinks per week, age of smoking initiation, smoking initiation, cigarettes per day, and smoking cessation with 433 psychiatric and behavioral traits in 4498 children and young adults (aged 8-21) of European ancestry from the Philadelphia neurodevelopmental cohort. After applying a false discovery rate multiple testing correction accounting for the number of PRS and traits tested, we identified 36 associations related to psychotic symptoms, emotion and age recognition social competencies, verbal reasoning, anxiety-related traits, parents' education, and substance use. These associations were independent of the genetic correlations among the alcohol-drinking and tobacco-smoking traits and those with cognitive performance, educational attainment, risk-taking behaviors, and psychopathology. The removal of participants endorsing substance use did not affect the associations of each PRS with psychiatric and behavioral traits identified as significant in the discovery analyses. Gene-ontology enrichment analyses identified several neurobiological processes underlying mechanisms of the PRS associations we report. In conclusion, we provide novel insights into the genetic overlap of smoking and drinking behaviors in children and young adults, highlighting their independence from psychopathology and substance use.

The Etiologic, Theory-Based, Ontogenetic Hierarchical Framework of Alcohol Use Disorder: A Translational Systematic Review of Reviews

Modern nosologies (e.g., ICD-11, DSM-5) for alcohol use disorder (AUD) and dependence prioritize reliability and clinical presentation over etiology, resulting in a diagnosis that is not always strongly grounded in basic theory and research. Within these nosologies, DSM-5 AUD is treated as a discrete, largely categorical, but graded, phenomenon, which results in additional challenges (e.g., significant phenotypic heterogeneity). Efforts to increase the compatibility between AUD diagnosis and modern conceptualizations of alcohol dependence, which describe it as dimensional and partially overlapping with other psychopathology (e.g., other substance use disorders) will inspire a stronger scientific framework and strengthen AUD's validity. We conducted a systematic review of 144 reviews to integrate addiction constructs and theories into a comprehensive framework with the aim of identifying fundamental mechanisms implicated in AUD. The product of this effort was the Etiologic, Theory-Based, Ontogenetic Hierarchical Framework (ETOH Framework) of AUD mechanisms, which outlines superdomains of cognitive control, reward, as well as negative valence and emotionality, each of which subsume narrower, hierarchically-organized components. We also outline opponent processes and self-awareness as key moderators of AUD mechanisms. In contrast with other frameworks, we recommend an increased conceptual role for negative valence and compulsion in AUD. The ETOH framework serves as a critical step towards conceptualizations of AUD as dimensional and heterogeneous. It has the potential to improve AUD assessment and aid in the development of evidence-based diagnostic measures that focus on key mechanisms in AUD, consequently facilitating treatment matching.

Genetics of substance use disorders: a review

Substance use disorders (SUDs) are prevalent and result in an array of negative consequences. They are influenced by genetic factors (h2 = ~50%). Recent years have brought substantial progress in our understanding of the genetic etiology of SUDs and related traits. The present review covers the current state of the field for SUD genetics, including the epidemiology and genetic epidemiology of SUDs, findings from the first-generation of SUD genome-wide association studies (GWAS), cautions about translating GWAS findings to clinical settings, and suggested prioritizations for the next wave of SUD genetics efforts. Recent advances in SUD genetics have been facilitated by the assembly of large GWAS samples, and the development of state-of-the-art methods modeling the aggregate effect of genome-wide variation. These advances have confirmed that SUDs are highly polygenic with many variants across the genome conferring risk, the vast majority of which are of small effect. Downstream analyses have enabled finer resolution of the genetic architecture of SUDs and revealed insights into their genetic relationship with other psychiatric disorders. Recent efforts have also prioritized a closer examination of GWAS findings that have suggested non-uniform genetic influences across measures of substance use (e.g. consumption) and problematic use (e.g. SUD). Additional highlights from recent SUD GWAS include the robust confirmation of loci in alcohol metabolizing genes (e.g. ADH1B and ALDH2) affecting alcohol-related traits, and loci within the CHRNA5-CHRNA3-CHRNB4 gene cluster influencing nicotine-related traits. Similar successes are expected for cannabis, opioid, and cocaine use disorders as sample sizes approach those assembled for alcohol and nicotine.

Early parent-child interactions and substance use disorder: An attachment perspective on a biopsychosocial entanglement

This review aims to elucidate environmental and genetic factors, as well as their epigenetic and neuroendocrine moderators, that may underlie the association between early childhood experiences and Substance Use Disorders (SUD), through the lens of parental attachment. Here we review those attachment-related studies that examined the monoaminergic systems, the hypothalamic pituitary adrenal stress response system, the oxytoninergic system, and the endogenous opioid system from a genetic, epigenetic, and neuroendocrine perspective. Overall, the selected studies point to a moderating effect of insecure attachment between genetic vulnerability and SUD, reasonably through epigenetic modifications. Preliminary evidence suggests that vulnerability to SUDs is related with hypo-methylation (e.g. hyper-expression) of high-risk polymorphisms on the monoaminergic and hypothalamic pituitary adrenal system and hyper-methylation (e.g. hypo-expressions) of protective polymorphisms on the opioid and oxytocin system. These epigenetic modifications may induce a cascade of neuroendocrine changes contributing to the subclinical and behavioural manifestations that precede the clinical onset of SUD. Protective and supportive parenting could hence represent a key therapeutic target to prevent addiction and moderate insecure attachment.

The Gut Microbiome and Substance Use Disorder

Substance use disorders (SUDs) remain a significant public health challenge, affecting tens of millions of individuals worldwide each year. Often comorbid with other psychiatric disorders, SUD can be poly-drug and involve several different substances including cocaine, opiates, nicotine, and alcohol. SUD has a strong genetic component. Much of SUD research has focused on the neurologic and genetic facets of consumption behavior. There is now interest in the role of the gut microbiome in the pathogenesis of SUD. In this review, we summarize current animal and clinical evidence that the gut microbiome is involved in SUD, then address the underlying mechanisms by which the gut microbiome interacts with SUD through metabolomic, immune, neurological, and epigenetic mechanisms. Lastly, we discuss methods using various inbred and outbred mice models to gain an integrative understanding of the microbiome and host genetic controls in SUD.

Association of the Uncoupling Protein 2-866 G/A Polymorphism with Family History and Duration of Tobacco Use Disorder in a Turkish Population

Background

A variety of substances cause neurotoxicity by increasing intracellular oxidative stress, followed by mitochondrial dysfunction. Uncoupling proteins (UCPs) act as membrane transport proteins and reduce reactive oxygen products and mitochondrial calcium influx. We aimed to study UCP2-866 G/A gene polymorphism in tobacco use disorder (TUD) by comparing genotype distributions between TUD patients and healthy controls considering clinical parameters.

Methods

One hundred eighteen patients with TUD and 96 healthy volunteers were included in the study. The diagnosis of the patients were then confirmed, based on the DSM-5 criteria. Polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) were used to determine UCP2 gene polymorphism.

Results

Our results demonstrated that the UCP2 genotype distribution and allele frequencies of the TUD patient group were significantly different from those of the control group. When the UCP2 genotype and the allele frequency distributions were compared between the two groups according to the family history of TUD in the patient group, the UCP2 genotype and allele frequency distributions were significantly different. The GG genotype or G allele percentage was significantly higher in patients with a family history of TUD, than the patients without a family history of TUD. Comparing clinical parameters based on the UCP2 genotype, the disorder's duration was significantly different between the groups of UCP2 genotype. The duration of TUD was significantly shorter in patients with GG genotype than other genotypes.

Conclusions

In summary, the UCP2-866 G/A gene polymorphism might be associated with family history and duration of TUD in Turkish patients.

Genetic basis of cannabis use: a systematic review

BACKGROUND

With the increase in cannabis use rates, cannabis use disorder is being reported as one of the most common drug use disorders globally. Cannabis use has several known physical, psychological, and social adverse events, such as altered judgement, poor educational outcomes, and respiratory symptoms. The propensity for taking cannabis and the development of a cannabis use disorder may be genetically influenced for some individuals. Heritability estimates suggest a genetic basis for cannabis use, and several genome-wide association studies (GWASs) have identified possible regions of association, albeit with inconsistent findings. This systematic review aims to summarize the findings from GWASs investigating cannabis use and cannabis use disorder.

METHODS

This systematic review incorporates articles that have performed a GWAS investigating cannabis use or cannabis use disorder. MEDLINE, Web of Science, EMBASE, CINAHL, GWAS Catalog, GWAS Central, and NIH Database of Genotype and Phenotype were searched using a comprehensive search strategy. All studies were screened in duplicate, and the quality of evidence was assessed using the quality of genetic association studies (Q-Genie) tool. All studies underwent qualitative synthesis; however, quantitative analysis was not feasible.

RESULTS

Our search identified 5984 articles. Six studies met our eligibility criteria and were included in this review. All six studies reported results that met our significance threshold of p ≤ 1.0 × 10-7. In total 96 genetic variants were identified. While meta-analysis was not possible, this review identified the following genes, ANKFN1, INTS7, PI4K2B, CSMD1, CST7, ACSS1, and SCN9A, to be associated with cannabis use. These regions were previously reported in different mental health conditions, however not in relation to cannabis use.

CONCLUSION

This systematic review summarized GWAS findings within the field of cannabis research. While a meta-analysis was not possible, the summary of findings serves to inform future candidate gene studies and replication efforts. Systematic Review Registration PROSPERO CRD42020176016.

Validity and utility of Hierarchical Taxonomy of Psychopathology (HiTOP): II. Externalizing superspectrum

The Hierarchical Taxonomy of Psychopathology (HiTOP) is an empirical effort to address limitations of traditional mental disorder diagnoses. These include arbitrary boundaries between disorder and normality, disorder co-occurrence in the modal case, heterogeneity of presentation within dis-orders, and instability of diagnosis within patients. This paper reviews the evidence on the validity and utility of the disinhibited externalizing and antagonistic externalizing spectra of HiTOP, which together constitute a broad externalizing superspectrum. These spectra are composed of elements subsumed within a variety of mental disorders described in recent DSM nosologies, including most notably substance use disorders and "Cluster B" personality disorders. The externalizing superspectrum ranges from normative levels of impulse control and self-assertion, to maladaptive disinhibition and antagonism, to extensive polysubstance involvement and personality psychopathology. A rich literature supports the validity of the externalizing superspectrum, and the disinhibited and antagonistic spectra. This evidence encompasses common genetic influences, environmental risk factors, childhood antecedents, cognitive abnormalities, neural alterations, and treatment response. The structure of these validators mirrors the structure of the phenotypic externalizing superspectrum, with some correlates more specific to disinhibited or antagonistic spectra, and others relevant to the entire externalizing superspectrum, underlining the hierarchical structure of the domain. Compared with traditional diagnostic categories, the externalizing superspectrum conceptualization shows improved utility, reliability, explanatory capacity, and clinical applicability. The externalizing superspectrum is one aspect of the general approach to psychopathology offered by HiTOP and can make diagnostic classification more useful in both research and the clinic.

Social vulnerabilities for substance use: Stressors, socially toxic environments, and discrimination and racism

Applying a social determinants of health framework, this review brings attention to evidence from social sciences and neuroscience on the role of selected social factors in individual and population-level vulnerability to substance use and substance use disorders (SUDs). The understanding that social vulnerability to substance use and SUDs is multifaceted and occurs across different levels of influence (individual, interpersonal, community, and societal) is underscored. We propose that socially based stressors play a critical role in creating vulnerability to substance use and SUDs, and as such, deserve greater empirical attention to further understand how they "get under the skin." Current knowledge from social sciences and neuroscience on the relationships among vulnerability to substance use resulting from stressors, exposure to socially toxic childhood environments, and racism and discrimination are summarized and discussed, as are implications for future research, practice, and policy. Specifically, we propose using a top-down approach to the examination of known, yet often unexplored, relationships between vulnerability to substance use and SUDs, related inequities, and potential differential effects across demographic groups. Finally, research gaps and promising areas of research, practice, and policy focused on ameliorating social vulnerabilities associated with substance use and SUDs across the lifespan are presented. This article is part of the special issue on 'Vulnerabilities to Substance Abuse'.