Genetics of Opioid Dependence: A Review of the Genetic Contribution to Opioid Dependence

Association Between Long-term Opioid Use in Family Members and Persistent Opioid Use After Surgery Among Adolescents and Young Adults

Importance

Prior studies have found a substantial risk of persistent opioid use among adolescents and young adults undergoing surgical and dental procedures. It is unknown whether family-level factors, such as long-term opioid use in family members, is associated with persistent opioid use.

Objective

To determine whether long-term opioid use in family members is associated with persistent opioid use among opioid-naive adolescents and young adults undergoing surgical and dental procedures.

Design, Setting, and Participants

This retrospective cohort study used data from a commercial insurance claims database for January 1, 2010, to June 30, 2016, to study 346 251 opioid-naive patients aged 13 to 21 years who underwent 1 of 11 surgical and dental procedures and who were dependents on a family insurance plan.

Exposures

Long-term opioid use in family members, defined as having 1 or more family members who (1) filled opioid prescriptions totaling a 120 days' supply or more during the 12 months before the procedure date or (2) filled 3 or more opioid prescriptions in the 90 days before the procedure date.

Main Outcomes and Measures

The main outcome measure was persistent opioid use, defined as 1 or more postoperative prescription opioid fills between 91 and 180 days among patients with an initial opioid prescription fill. Generalized estimating equations with robust SEs clustered at the family level were used to model persistent opioid use as a function of long-term opioid use among family members, controlling for procedure, total morphine milligram equivalents of the initial fill, and patient and family characteristics.

Results

A total of 346 251 patients (mean [SD] age, 17.0 [2.3] years; 175 541 [50.7%] female) were studied. Among these patients, 257 085 (74.3%) had an initial opioid fill. Among patients with an initial opioid fill, 11 016 (4.3%) had long-term opioid use in a family member. Persistent opioid use occurred in 453 patients (4.1%) with long-term opioid use in a family member compared with 5940 patients (2.4%) without long-term opioid use in a family member (adjusted odds ratio, 1.54; 95% CI, 1.39-1.71).

Conclusion and Relevance

The findings suggest that long-term opioid use among family members is associated with persistent opioid use among opioid-naive adolescents and young adults undergoing surgical and dental procedures. Physicians should screen young patients for long-term opioid use in their families and implement heightened efforts to prevent opioid dependence among patients with this important risk factor.

Opioid Neurobiology, Neurogenetics and Neuropharmacology in Zebrafish

Despite the high prevalence of medicinal use and abuse of opioids, their neurobiology and mechanisms of action are not fully understood. Experimental (animal) models are critical for improving our understanding of opioid effects in vivo. As zebrafish (Danio rerio) are increasingly utilized as a powerful model organism in neuroscience research, mounting evidence suggests these fish as a useful tool to study opioid neurobiology. Here, we discuss the zebrafish opioid system with specific focus on opioid gene expression, existing genetic models, as well as its pharmacological and developmental regulation. As many human brain diseases involve pain and aberrant reward, we also summarize zebrafish models relevant to opioid regulation of pain and addiction, including evidence of functional interplay between the opioid system and central dopaminergic and other neurotransmitter mechanisms. Additionally, we critically evaluate the limitations of zebrafish models for translational opioid research and emphasize their developing utility for improving our understanding of evolutionarily conserved mechanisms of pain-related, addictive, affective and other behaviors, as well as for fostering opioid-related drug discovery.

Implementation and Evaluation of an Opioid Risk Questionnaire in the Outpatient Plastic Surgery Setting

Most patients undergoing plastic and cosmetic surgery are prescribed an opioid for postoperative pain control. With the advent of the opioid epidemic in our country, screening for opioid risk has become a topic of many health care discussions. However, there has been little mention of using an opioid risk questionnaire specific to the outpatient plastic surgery setting. This project consisted of distribution of an opioid risk questionnaire to adult patients undergoing outpatient plastic surgery. Data were collected at preoperative appointments from participating patients (n = 27). Although the sample size was small, two patients (7%) were identified as having a history of substance abuse, and both of those patients reported they had also received treatment for their substance abuse. In addition, six patients (22%) reported having a family history of substance abuse. Such findings suggest that clinicians working in outpatient plastic surgery should screen their patients for substance abuse and misuse.

Genetic association of human Corticotropin-Releasing Hormone Receptor 1 (CRHR1) with Internet gaming addiction in Korean male adolescents

BACKGROUND

The number of people with Internet gaming addiction (IGA) is increasing around the world. IGA is known to be associated with personal characteristics, psychosocial factors, and physiological factors. However, few studies have examined the genetic factors related to IGA. This study aimed to investigate the association between IGA and stress-related genetic variants.

METHODS

This cross-sectional study was conducted with 230 male high school students in a South Korean city. We selected five stress-related candidate genes: DAT1, DRD4, NET8, CHRNA4, and CRHR1. The DAT1 and DRD4 genes were genotyped by polymerase chain reaction, and the NET8, CHRNA4, and CRHR1 genes were genotyped by pyrosequencing analysis. We performed a Chi-square test to examine the relationship of these five candidate genes to IGA.

RESULTS

Having the AA genotype and the A allele of the CRHR1 gene (rs28364027) was associated with higher odds of belonging to the IGA participant group (p = .016 and p = .021, respectively) than to the non-IGA group. By contrast, the DAT1, DRD4, NET8, and CHRNA4 gene polymorphisms showed no significant difference between the IGA group and control group.

CONCLUSIONS

These results indicate that polymorphism of the CRHR1 gene may play an important role in IGA susceptibility in the Korean adolescent male population. These findings provide a justification and foundation for further investigation of genetic factors related to IGA.

Genome-wide Association Study Identifies a Regulatory Variant of RGMA Associated With Opioid Dependence in European Americans

BACKGROUND

Opioid dependence (OD) is at epidemic levels in the United States. Genetic studies can provide insight into its biology.

METHODS

We completed an OD genome-wide association study in 3058 opioid-exposed European Americans, 1290 of whom met criteria for a DSM-IV diagnosis of OD. Analysis used DSM-IV criterion count.

RESULTS

By meta-analysis of four cohorts, Yale-Penn 1 (n = 1388), Yale-Penn 2 (n = 996), Yale-Penn 3 (n = 98), and SAGE (Study of Addiction: Genetics and Environment) (n = 576), we identified a variant on chromosome 15, rs12442183, near RGMA, associated with OD (p = 1.3 × 10^-8). The association was also genome-wide significant in Yale-Penn 1 taken individually and nominally significant in two of the other three samples. The finding was further supported in a meta-analysis of all available opioid-exposed African Americans (n = 2014 [1106 meeting DSM-IV OD criteria]; p = 3.0 × 10^-3) from three cohorts; there was nominal significance in two of these samples. Thus, of seven subsamples examined in two populations, one was genome-wide significant, and four of six were nominally (or nearly) significant. RGMA encodes repulsive guidance molecule A, which is a central nervous system axon guidance protein. Risk allele rs12442183*T was correlated with higher expression of a specific RGMA transcript variant in frontal cortex (p = 2 × 10^-3). After chronic morphine injection, the homologous mouse gene (Rgma) was upregulated in C57BL/6J striatum. Coexpression analysis of 1301 brain samples revealed that RGMA messenger RNA expression was associated with that of four genes implicated in other psychiatric disorders, including GRIN1.

CONCLUSIONS

This is the first study to demonstrate an association of RGMA with OD. It provides a new lead into our understanding of OD pathophysiology.

Contribution of psychiatric diagnoses to extent of opioid prescription in the first year post-head and neck cancer diagnosis: A longitudinal study

PURPOSE

The purpose of this study was to determine, within the first-year post-head and neck cancer (HNC) diagnosis, the contribution of past and upon HNC psychiatric diagnoses (ie, substance use disorder, major depressive disorder, and anxiety disorder) to the extent (ie, cumulated dose) of opioid prescription.

METHODS

Prospective longitudinal study of 223 consecutive adults (on 313 approached; 72% participation) newly diagnosed (<2 weeks) with a first occurrence of primary HNC, including Structured Clinical Interviews for DSM-IV disorders, validated psychometric measures, and medical chart reviews. Opioid doses were translated into standardized morphine milligram equivalents (MME) using CDC guidelines. A model of variables was tested using multiple linear regression.

RESULTS

Fifty-five percent (123/223) of patients received opioids at some point during the first 12 months post-HNC diagnosis, 37.7% (84/223) upon HNC diagnosis (pre-treatment), 40.8% (91/223) during treatments, and 31.4% (70/223) post-treatment. The multiple linear regression indicated that an AD (P = 0.04) upon HNC diagnosis in early stage contributes to cumulated MME dose in the first year post-HNC diagnosis.

CONCLUSION

This study underlines how anxiety has important repercussions on the management of pain and illustrates the importance of screening for AD upon HNC diagnosis to allow for early prophylactic treatment and support.

Implication of OPRM1 A118G Polymorphism in Opioids Addicts in Pakistan: In vitro and In silico Analysis

Single nucleotide polymorphism in OPRM1 gene is associated with hedonic and reinforcing consequences of opioids. Risk and protective alleles may vary in different populations. One hundred healthy controls and 100 opioids (predominantly heroin) addicts from Pakistani origin were genotyped for A118G (N40D) polymorphism in OPRM1. Structural and functional impact of the polymorphism on encoded protein was predicted by in silico analysis. Results show significant association between homozygous GG genotype and opioid addiction in Pakistani population (p value = 0.016). In silico analysis by SIFT (TI = 0.61), PolyPhen (PISC = 0.227), PANTHER (subPSEC = -1.7171), and SNP effect predicted this SNP benign for encoded protein. Superimposing wild-type and mutated proteins by MODELLER shows no change (RMSD = 0.1) in extracellular ligand binding domain of μ-opioid receptor. However, Haploreg and RegulomeDB predicted OPRM1 gene repression by chromatin condensation and increased binding affinity of RXRA transcription factor that may reduce protein translation and hence the number of available receptors to bind with drugs, which may trigger underlying mechanisms for opioids addiction. Thus, this study outlines causal relationship between opioids addiction and genetic predisposition in Pakistani population.

GABRA2 rs279858-linked variants are associated with disrupted structural connectome of reward circuits in heroin abusers

The reward system plays a vital role in drug addiction. The purpose of this study is to investigate the structural connectivity characteristics and driving-control subnetwork patterns of reward circuits in heroin abusers and assess the genetic modulation on the reward network. We first defined the reward network based on systematic literature review, and built the reward network based on diffusion tensor imaging data of 78 heroin abusers (HAs) and 79 healthy controls (HCs) using structural connectomics. Then we assessed genetic factors that might modulate changes in the reward network by performing imaging-genetic screening for 22 addiction-related polymorphisms. The genetic association was validated by performing genetic associations (1032 HAs and 2863 HCs) and expanded-variant analysis. Finally, we estimated the association between these genetic variations, reward network, and clinical performance. We found that HAs had widespread deficiencies in the structural connectivity of the reward circuit (center in VTA-linked connections), which correlated with cognition deficiency. The disruptions synchronously were shown on the reward driving system and reward control system. GABRA2 rs279858-linked variants might be a key genetic modulator for heroin vulnerability by affecting the connections of reward network and cognition. The role of the reward network connections that mediates the effects of rs279858 on cognition would be disrupted by heroin addiction. These findings provide new insights into the neurocircuitry and genetic mechanisms of addiction.

Opioid Initiation to Substance Use Treatment: "They Just Want to Feel Normal"

BACKGROUND

Opioid use disorder has drastically increased in recent years within adult populations. Limited understanding exists regarding how people enter medication-assisted treatment (MAT) for opioid use disorder-particularly those who initiate opioid use to treat a painful condition.

OBJECTIVES

This research examines the process involved when adults first initiate the use of opioid medicines to treat pain through enrollment in an outpatient MAT program.

METHODS

Grounded theory methodology guided the study. Data analysis included interpretation of interview transcripts from 10 adults who were enrolled in a single outpatient MAT program in the Pacific Northwest. Inclusion criteria were adults in MAT reporting that their initial use of opioids was to treat their pain. Corbin and Strauss' approach to theory development was followed.

RESULTS

A newly developed theory titled Living With Persistent Pain: From Opioid Initiation to Substance Use Treatment was supported by three predominant categories emerging from the data: "addiction pathway," "becoming normal," and "relationship spectrum." The core category "living with pain" was described as a complex and tumultuous process spanning the emergence of pain, to the initial use of opioid medicines, through opioid addiction and MAT. A notable aspect of this process was the turning point to enter MAT, which was both helped and hindered by significant relationships.

CONCLUSIONS

The decision to enter MAT for opioid addiction was key to helping participants gain a sense of normalcy. Insights gained from participants' experiences-particularly in relationships with healthcare providers-can be used to guide treatment approaches.

Pharmacogenetics in Pain Treatment

Pain is an unpleasant feeling usually resulting from tissue damage that can persist along weeks, months, or even years after the injury, turning into pathological chronic pain, the leading cause of disability. Currently, pharmacology interventions are usually the first-line therapy but there is a highly variable analgesic drug response. Pharmacogenetics (PGx) offers a means to identify genetic biomarkers that can predict individual analgesic response opening doors to precision medicine. PGx analyze the way in which the presence of variations in the DNA sequence (single-nucleotide polymorphisms, SNPs) could be responsible for portions of the population reaching different levels of pain relief (phenotype) due to gene interference in the drug mechanism of action (pharmacodynamics) and/or its concentration at the place of action (pharmacokinetics). SNPs in the cytochrome P450 enzymes genes (CYP2D6) influence metabolism of codeine, tramadol, hydrocodone, oxycodone, and tricyclic antidepressants. Blood concentrations of some NSAIDs depend on CYP2C9 and/or CYP2C8 activity. Additional candidate genes encode for opioid receptors, transporters, and other molecules important for pharmacotherapy in pain management. However, PGx studies are often contradictory, slowing the uptake of this information. This is likely due, in large part, to a lack of robust evidence demonstrating clinical utility and to its polygenic response modulated by other exogenous or epigenetics factors. Novel therapies, including targeting of epigenetic changes and gene therapy-based approaches, broaden future options to improve understanding of pain and the treatment of people who suffer it.

Use and Misuse of Opioids in Chronic Pain

The prescribing of opioid analgesics for pain management-particularly for management of chronic noncancer pain (CNCP)-has increased more than fourfold in the United States since the mid-1990s. Yet there is mounting evidence that opioids have only limited effectiveness in the management of CNCP, and the increased availability of prescribed opioids has contributed to upsurges in opioid-related addiction cases and overdose deaths. These concerns have led to critical revisiting and modification of prior pain management practices (e.g., guidelines from the Centers for Disease Control and Prevention), but the much-needed changes in clinical practice will be facilitated by a better understanding of the pharmacology and behavioral effects of opioids that underlie both their therapeutic effects (analgesia) and their adverse effects (addiction and overdose). With these goals in mind, this review first presents an overview of the contemporary problems associated with opioid management of CNCP and the related public health issues of opioid diversion, overdose, and addiction. It then discusses the pharmacology underlying the therapeutic and main adverse effects of opioids and its implications for clinical management of CNCP within the framework of recent clinical guidelines for prescribing opioids in the management of CNCP.

Drug Addiction: From Neuroscience to Ethics

In the present paper, we suggest a potential new ethical analysis of addiction focusing on the relationship between aware and unaware processing in the brain. We take the case of the opioids epidemics to argue that a consideration of both aware and unaware processing provides a more comprehensive ethical framework to discuss the ethical issues raised by addiction. Finally, our hypothesis is that in addition to identified Central Nervous System's neuronal/neurochemical factors contributing to addictive dynamics, the socio-economic status plays a causal role through epigenetic processes, originating the need for additional reward in the brain. This provides a strong base for a socio-political form of responsibility for preventing and managing addiction crisis.

Association Between Initial Opioid Prescribing Patterns and Subsequent Long-Term Use Among Opioid-Naïve Patients: A Statewide Retrospective Cohort Study

BACKGROUND

Long-term efficacy of opioids for non-cancer pain is unproven, but risks argue for cautious prescribing. Few data suggest how long or how much opioid can be prescribed for opioid-naïve patients without inadvertently promoting long-term use.

OBJECTIVE

To examine the association between initial opioid prescribing patterns and likelihood of long-term use among opioid-naïve patients.

DESIGN

Retrospective cohort study; data from Oregon resident prescriptions linked to death certificates and hospital discharges.

PARTICIPANTS

Patients filling opioid prescriptions between October 1, 2012, and September 30, 2013, with no opioid fills for the previous 365 days. Subgroup analyses examined patients under age 45 who did not die in the follow-up year, excluding most cancer or palliative care patients.

MAIN MEASURES

Exposure: Numbers of prescription fills and cumulative morphine milligram equivalents (MMEs) dispensed during 30 days following opioid initiation ("initiation month").

OUTCOME

Proportion of patients with six or more opioid fills during the subsequent year ("long-term users").

KEY RESULTS

There were 536,767 opioid-naïve patients who filled an opioid prescription. Of these, 26,785 (5.0 %) became long-term users. Numbers of fills and cumulative MMEs during the initiation month were associated with long-term use. Among patients under age 45 using short-acting opioids who did not die in the follow-up year, the adjusted odds ratio (OR) for long-term use among those receiving two fills versus one was 2.25 (95 % CI: 2.17, 2.33). Compared to those who received < 120 total MMEs, those who received between 400 and 799 had an OR of 2.96 (95 % CI: 2.81, 3.11). Patients initiating with long-acting opioids had a higher risk of long-term use than those initiating with short-acting drugs.

CONCLUSIONS

Early opioid prescribing patterns are associated with long-term use. While patient characteristics are important, clinicians have greater control over initial prescribing. Our findings may help minimize the risk of inadvertently initiating long-term opioid use.

Analysis of morphine responses in mice reveals a QTL on Chromosome 7

In this study we identified a quantitative trait locus (QTL) on mouse Chromosome 7 associated with locomotor activity and rearing post morphine treatment. This QTL was revealed after correcting for the effects of another QTL peak on Chromosome 10 using composite interval mapping. The positional candidate genes are Syt9 and Ppfibp2. Several other genes within the interval are linked to neural processes, locomotor activity, and the defensive response to harmful stimuli.

Association between genetic variations of NMDA receptor NR3 subfamily genes and heroin addiction in male Han Chinese

Growing amounts of evidence suggest that N-Methyl-d-aspartate (NMDA) receptor mediated glutamate neurotransmission may be involved in the pathophysiology of drug dependence. The NMDA receptor consists of three subfamilies (NR1, NR2, and NR3). The ability of subunit NR3 to negatively modulate the NMDA receptor function makes it an attractive candidate gene of heroin addiction. The purpose of this study is to explore the association between four single nucleotide polymorphisms (SNPs) of NR3 gene and heroin addiction. Genotyping of two SNPs (rs3739722 and rs17189632) in GRIN3A and two SNPs (rs4807399 and rs2240158) in GRIN3B was performed using TaqMan SNP genotyping method. The association between heroin addiction and these SNPs was assessed among 332 male heroin dependent patients and 400 male normal control subjects. The results showed the genotype and allele frequencies of rs17189632 and rs2240158 were significantly different between the cases and the controls (nominal P values were 0.0284, 0.0136 for rs17189632; 0.0048, 0.0013 for rs2240158, respectively). After Bonferroni correction, rs2240158 of GRIN3B was still found to be associated with heroin addiction. The frequencies of haplotype C-A at GRIN3A (rs3739722-rs17189632) and of C-C and C-T at GRIN3B (rs4807399-rs2240158) differed significantly between the cases and the controls. The genotype and allele distributions of rs3739722 and rs4807399 were not significantly different between in the cases and in the controls (P>0.05). These results suggest that GRIN3A rs17189632 and GRIN3B rs2240158 may contribute to the susceptibility of heroin addiction.

Who Benefits from Chronic Opioid Therapy? Rethinking the Question of Opioid Misuse Risk

Beginning in the late 1990s, a movement began within the pain management field focused upon the underutilization of opioids, thought to be a potentially safe and effective class of pain medication. Concern for addiction and misuse were present at the start of this shift within pain medicine, and an emphasis was placed on developing reliable and valid methods and measures of identifying those at risk for opioid misuse. Since that time, the evidence for the safety and effectiveness of chronic opioid therapy (COT) has not been established. Rather, the harmful, dose-dependent deleterious effects have become clearer, including addiction, increased risk of injuries, respiratory depression, opioid induced hyperalgesia, and death. Still, many individuals on low doses of opioids for long periods of time appear to have good pain control and retain social and occupational functioning. Therefore, we propose that the question, “Who is at risk of opioid misuse?” should evolve to, “Who may benefit from COT?” in light of the current evidence.

Adding Genetic Testing to Evidence-Based Guidelines to Determine the Safest and Most Effective Chronic Pain Treatment for Injured Workers

Published guidelines for treating injured workers include the need for personalized treatment to manage chronic pain symptoms and increase functional status. However, they often fail to clarify how to objectively personalize these treatments. Further, certain patients need analgesic relief beyond the short term. In these cases, it is not sufficient or reasonable to utilize the typical broad protocol-based justifications for reduction of opioids and other medications in a haphazard manner based purely on poor response, without attempting to elucidate possible pharmacogenetic reasons for this. These guidelines acknowledge the problem of substance abuse and set forth methods for treatment and prevention. Although it has been established in the scientific community that an individual's experience of pain and likelihood for addiction both have genetic components, genetic testing is not routinely included as part of the overall treatment plan for injured workers with chronic pain. Because decisions in cases of workplace injury should be based on scientific evidence, genetic testing results can add some objective information to the existing subjective and objective clinical data; help ascertain the efficacy and potential for toxicity of treatment; and therefore provide more information for accurate clinical decisions. We propose the addition of genetic testing to consensus guidelines for treating injured workers in order to improve patients' functional status, increase productivity, improve safety of prescribing, decrease the likelihood of substance abuse, and save on overall healthcare costs.

Replication of ZNF804A gene variant associations with risk of heroin addiction

Heroin addiction is heritable, but few specific genetic variants have been reproducibly associated with this disease. The zinc finger protein 804A (ZNF804A) gene is a biologically plausible susceptibility gene for heroin addiction, given its function as a transcription factor in human brain. Novel associations of two common ZNF804A single nucleotide polymorphisms (SNPs), rs7597593 and rs1344706, with heroin addiction have been reported in Han Chinese. Both SNPs have also been implicated for regulating ZNF804A expression in human brain, including the addiction-relevant dorsolateral prefrontal cortex. In this independent replication study, we tested the rs7597593 and rs1344706 SNP genotypes and their corresponding haplotypes for association with heroin addiction using cases drawn from the Urban Health Study and population controls: total N = 10 757 [7095 European Americans (EAs) and 3662 African Americans (AAs)]. We independently replicated both ZNF804A SNP associations in EAs: the rs7597593-T (P = 0.016) and rs1344706-A (P = 0.029) alleles both being associated with increased risk of heroin addiction, consistent with the prior report. Neither SNP was associated in AAs alone, but meta-analysis across both ancestry groups resulted in significant associations for rs1344706-A [P = 0.016, odds ratio (95% confidence interval) = 1.13 (1.02-1.25)] and its haplotype with rs7597593-T [P = 0.0067, odds ratio (95% confidence interval) = 1.16 (1.04-1.29)]. By showing consistent associations across independent studies and diverse ancestry groups, our study provides evidence that these two ZNF804A SNPs and their risk haplotype are among the few replicable genetic associations with heroin addiction.