The Genetics of Addictions: Uncovering the Genes

Patterns of Drug Use and Related Factors Among Prisoners in Iran: Results from the National Survey in 2015

Drug use by prisoners is one of the world's most important problems. We sought to determine the pattern of drug use behavior and related factors among prisoners of Iran in 2015. This cross-sectional study was part of the bio-behavioral surveillance survey conducted among 6200 prisoners in 26 prison sites in Iran who were selected through multi-stage sampling. Data were collected through questionnaires and interviews which inquired about participants' demographics and drug use behaviors. We analyzed study data using descriptive statistics, and crude and adjusted logistic regressions, in STATA-12. Of all prisoners, 74.0% had a history of lifetime drug use, and 16.6% of drug users had a history of lifetime injection drug use (IDU). According to the results of a multivariate logistic regression, male sex, being between the ages of 24 and 45, having a history of imprisonment, and having a history of lifetime high-risk sexual behavior were significant risk factors for lifetime drug use. Also, male sex, single status, and a history of previous imprisonment were significant risk factors for lifetime IDU. The prevalence of drug use in Iran's prison population is high and alarming. There is a continuing need for harm reduction programs, including the methadone maintenance treatment, among imprisoned drug users and IDUs.

The genetics and epigenetics of Neonatal Abstinence Syndrome

Neonatal abstinence syndrome (NAS) due to in-utero opioid exposure is a growing epidemic with significant variability in clinical presentation and severity. Currently, NAS severity cannot be predicted based on clinical factors alone. To date, small studies have identified genetic variants in opioid receptor and stress response genes that are associated with differences in NAS pharmacologic treatment rates and length of hospitalization. In addition, epigenetic variation in the mu opioid receptor (OPRM1) gene has been associated with differences in NAS hospitalization outcomes. Examination of maternal genetic and epigenetic profiles may assist in prediction of NAS severity. Large-scale genomic studies are needed to elucidate the genetic architecture of and epigenetic modification related to NAS in order to develop more tailored personalized treatments for NAS.

Association of maternal and infant variants in PNOC and COMT genes with neonatal abstinence syndrome severity

BACKGROUND AND OBJECTIVES

There is significant variability in severity of neonatal abstinence syndrome (NAS) due to in utero opioid exposure. Our previous study identified single nucleotide polymorphisms (SNPs) in the prepronociceptin (PNOC) and catechol-O-methyltransferase (COMT) genes that were associated with differences in NAS outcomes. This study looks at the same SNPs in PNOC and COMT in an independent cohort in an attempt to replicate previous findings.

METHODS

For the replication cohort, full-term opioid-exposed newborns and their mothers (n = 113 pairs) were studied. A DNA sample was obtained and genotyped for five SNPs in the PNOC and COMT genes. The association of each SNP with NAS outcomes (length of hospitalization, need for pharmacologic treatment, and total opioid days) was evaluated, with an experiment-wise significance level set at α < .003 and point-wise level of α < .05. SNP associations in a combined cohort of n = 199 pairs (replication cohort plus 86 pairs previously reported), were also examined.

RESULTS

In the replication cohort, mothers with the COMT rs4680 G allele had infants with a reduced risk for treatment with two medications for NAS (adjusted OR = .5, p = .04), meeting point-wise significance. In the combined cohort, infants with the PNOC rs4732636 A allele had a reduced need for medication treatment (adjusted OR 2.0, p = .04); mothers with the PNOC rs351776 A allele had infants who were treated more often with two medications (adjusted OR 2.3, p = .004) with longer hospitalization by 3.3 days (p = .01). Mothers with the COMT rs740603 A allele had infants who were less often treated with any medication (adjusted OR .5, p = .02). Though all SNP associations all met point wise and clinical significance, they did not meet the experiment-wise significance threshold.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

We found differences in NAS outcomes depending on PNOC and COMT SNP genotype. This has important implications for identifying infants at risk for severe NAS who could benefit from tailored treatment regimens. Further testing in a larger sample is warranted. This has important implications for prenatal prediction and personalized treatment regimens for infants with NAS. (Am J Addict 2017;26:42-49).

Variations in opioid receptor genes in neonatal abstinence syndrome

BACKGROUND

There is significant variability in the severity of neonatal abstinence syndrome (NAS) due to in-utero opioid exposure. We wanted to determine if single nucleotide polymorphisms (SNPs) in key candidate genes contribute to this variability.

METHODS

Full-term opioid-exposed newborns and their mothers (n=86 pairs) were studied. DNA was genotyped for 80 SNPs from 14 genes utilizing a custom designed microarray. The association of each SNP with NAS outcomes was evaluated.

RESULTS

SNPs in two opioid receptor genes in the infants were associated with worse NAS severity: (1) The PNOC rs732636 A allele (OR=3.8, p=0.004) for treatment with 2 medications and a longer hospital stay (LOS) of 5.8 days (p=0.01), and (2) The OPRK1 rs702764 C allele (OR=4.1, p=0.003) for treatment with 2 medications. The OPRM1 rs1799971 G allele (β=-6.9 days, p=0.02) and COMT rs740603 A allele (β=-5.3 days, p=0.01) were associated with shorter LOS. The OPRD1 rs204076 A allele in the mothers was associated with a longer LOS by 6.6 days (p=0.008). Results were significant point-wise but did not meet the experiment-wide significance level.

CONCLUSIONS

These findings suggest that SNPs in opioid receptor and the PNOC genes are associated with NAS severity. However, further testing in a large sample is warranted. This has important implications for prenatal prediction and personalized treatment regimens for infants at highest risk for severe NAS.

Epigenetic variation in the mu-opioid receptor gene in infants with neonatal abstinence syndrome

OBJECTIVE

Neonatal abstinence syndrome (NAS) from in utero opioid exposure is highly variable with genetic factors appearing to play an important role. Epigenetic changes in cytosine:guanine (CpG) dinucleotide methylation can occur after drug exposure and may help to explain NAS variability. We correlated DNA methylation levels in the mu-opioid receptor (OPRM1) promoter in opioid-exposed infants with NAS outcomes.

STUDY DESIGN

DNA samples from cord blood or saliva were analyzed for 86 infants who were being treated for NAS according to institutional protocol. Methylation levels at 16 OPRM1 CpG sites were determined and correlated with NAS outcome measures, including need for treatment, treatment with ≥ 2 medications, and length of hospital stay. We adjusted for covariates and multiple genetic testing.

RESULTS

Sixty-five percent of infants required treatment for NAS, and 24% required ≥ 2 medications. Hypermethylation of the OPRM1 promoter was measured at the -10 CpG in treated vs nontreated infants (adjusted difference δ = 3.2% [95% CI, 0.3-6.0%], P = .03; nonsignificant after multiple testing correction). There was hypermethylation at the -14 (δ = 4.9% [95% CI, 1.8%-8.1%], P = .003), -10 (δ = 5.0% [95% CI, 2.3-7.7%], P = .0005), and +84 (δ = 3.5% [95% CI, 0.6-6.4], P = .02) CpG sites in infants requiring ≥ 2 medications, which remained significant for -14 and -10 after multiple testing correction.

CONCLUSIONS

Increased methylation within the OPRM1 promoter is associated with worse NAS outcomes, consistent with gene silencing.

La m&eacute;thodologie au service de l&apos;avancement des connaissances en mati&egrave;re de jeux de hasard et d&apos;argent

Cet article passe en revue trois méthodologies susceptibles de faire avancer les connaissances en matière de jeux de hasard et d'argent: la méthodologie longitudinale, la méthodologie expérimentale et la méthodologie génétique. Des exemples servent à illustrer comment ces méthodologies permettent: a) de documenter le développement des habitudes et des problèmes de jeu; b) d'identifier les facteurs de risque à présomption causale associés à leur apparition, à leur maintien ou à leur aggravation; c) d'explorer la signification de la cooccurrence des problèmes de jeu avec d'autres problèmes de santé mentale; d) d'analyser les possibles liens transactionnels entre les problèmes de jeu et d'autres problèmes d'adaptation; et, enfin, e) de dégager des leçons par rapport à la modélisation théorique et à l'intervention préventive.

DRD4 polymorphism moderates the effect of alcohol consumption on social bonding

Development of interpersonal relationships is a fundamental human motivation, and behaviors facilitating social bonding are prized. Some individuals experience enhanced reward from alcohol in social contexts and may be at heightened risk for developing and maintaining problematic drinking. We employed a 3 (group beverage condition) ×2 (genotype) design (N = 422) to test the moderating influence of the dopamine D4 receptor gene (DRD4 VNTR) polymorphism on the effects of alcohol on social bonding. A significant gene x environment interaction showed that carriers of at least one copy of the 7-repeat allele reported higher social bonding in the alcohol, relative to placebo or control conditions, whereas alcohol did not affect ratings of 7-absent allele carriers. Carriers of the 7-repeat allele were especially sensitive to alcohol's effects on social bonding. These data converge with other recent gene-environment interaction findings implicating the DRD4 polymorphism in the development of alcohol use disorders, and results suggest a specific pathway by which social factors may increase risk for problematic drinking among 7-repeat carriers. More generally, our findings highlight the potential utility of employing transdisciplinary methods that integrate genetic methodologies, social psychology, and addiction theory to improve theories of alcohol use and abuse.

Drugs and addiction: an introduction to epigenetics

Addiction is a debilitating psychiatric disorder, with a complex aetiology involving the interaction of inherited predispositions and environmental factors. Emerging evidence suggests that epigenetic alterations to the genome, including DNA methylation and histone modifications, are important mechanisms underlying addiction and the neurobiological response to addictive substances. In this review, we introduce the reader to epigenetic mechanisms and describe a potential role for dynamic epigenetic changes in mediating addictive behaviours via long-lasting changes in gene expression. We summarize recent findings from both molecular and behavioural experiments elucidating the role of epigenetic changes in mediating the addictive potential of various drugs of abuse, including cocaine, amphetamine and alcohol. The implications of these findings for molecular studies of addiction and the future development of novel therapeutic interventions are also discussed.