Risk of Heroin Dependence in Newly Incident Heroin Users

Cannabis use to manage opioid cravings among people who use unregulated opioids during a drug toxicity crisis

BACKGROUND

Accumulating evidence has indicated that cannabis substitution is often used as a harm reduction strategy among people who use unregulated opioids (PWUO) and people living with chronic pain. We sought to investigate the association between cannabis use to manage opioid cravings and self-reported changes in opioid use among structurally marginalized PWUO.

METHODS

The data were collected from a cross-sectional questionnaire administered to PWUO in Vancouver, Canada. Binary logistic regression was used to analyze the association between cannabis use to manage opioid cravings and self-reported changes in unregulated opioid use.

RESULTS

A total of 205 people who use cannabis and opioids were enrolled in the present study from December 2019 to November 2021. Cannabis use to manage opioid cravings was reported by 118 (57.6%) participants. In the multivariable analysis, cannabis use to manage opioid cravings (adjusted Odds Ratio [aOR] = 2.13, 95% confidence interval [CI]: 1.07, 4.27) was significantly associated with self-reported reductions in opioid use. In the sub-analyses of pain, cannabis use to manage opioid cravings was only associated with self-assessed reductions in opioid use among people living with moderate to severe pain (aOR = 4.44, 95% CI: 1.52, 12.97). In the sub-analyses of males and females, cannabis use to manage opioid cravings was only associated with self-assessed reductions in opioid use among females (aOR = 8.19, 95% CI: 1.20, 55.81).

CONCLUSIONS

These findings indicate that cannabis use to manage opioid cravings is a prevalent motivation for cannabis use among PWUO and is associated with self-assessed reductions in opioid use during periods of cannabis use. Increasing the accessibility of cannabis products for therapeutic use may be a useful supplementary strategy to mitigate exposure to unregulated opioids and associated harm during the ongoing drug toxicity crisis.

Cross-phenotype relationship between opioid use disorder and suicide attempts: new evidence from polygenic association and Mendelian randomization analyses

Clinical epidemiological studies have found high co-occurrence between suicide attempts (SA) and opioid use disorder (OUD). However, the patterns of correlation and causation between them are still not clear due to psychiatric confounding. To investigate their cross-phenotype relationship, we utilized raw phenotypes and genotypes from >150,000 UK Biobank samples, and genome-wide association summary statistics from >600,000 individuals with European ancestry. Pairwise association and a potential bidirectional relationship between OUD and SA were evaluated with and without controlling for major psychiatric disease status (e.g., schizophrenia, major depressive disorder, and alcohol use disorder). Multiple statistical and genetics tools were used to perform epidemiological association, genetic correlation, polygenic risk score prediction, and Mendelian randomizations (MR) analyses. Strong associations between OUD and SA were observed at both the phenotypic level (overall samples [OR = 2.94, P = 1.59 ×10-14]; non-psychiatric subgroup [OR = 2.15, P = 1.07 ×10-3]) and the genetic level (genetic correlation rg = 0.38 and 0.5 with or without conditioning on psychiatric traits, respectively). Consistently, increasing polygenic susceptibility to SA is associated with increasing risk of OUD (OR = 1.08, false discovery rate [FDR] =1.71 ×10-3), and similarly, increasing polygenic susceptibility to OUD is associated with increasing risk of SA (OR = 1.09, FDR = 1.73 ×10-6). However, these polygenic associations were much attenuated after controlling for comorbid psychiatric diseases. A combination of MR analyses suggested a possible causal association from genetic liability for SA to OUD risk (2-sample univariable MR: OR = 1.14, P = 0.001; multivariable MR: OR = 1.08, P = 0.001). This study provided new genetic evidence to explain the observed OUD-SA comorbidity. Future prevention strategies for each phenotype needs to take into consideration of screening for the other one.

A National Strategy for Preventing Substance and Opioid Use Disorders Through Evidence-Based Prevention Programming that Fosters Healthy Outcomes in Our Youth

The recently released National Drug Control Strategy (2022) from the White House Office of National Drug Control Policy (ONDCP) lays out a comprehensive plan to, not only enhance access to treatment and increase harm reduction strategies, but also increase implementation of evidence-based prevention programming at the community level. Furthermore, the Strategy provides a framework for enhancing our national data systems to inform policy and to evaluate all components of the plan. However, not only are there several missing components to the Strategy that would assure its success, but there is a lack of structure to support a national comprehensive service delivery system that is informed by epidemiological data, and trains and credentials those delivering evidence-based prevention, treatment, and harm reduction/public health interventions within community settings. This paper provides recommendations for the establishment of such a structure with an emphasis on prevention. Systematically addressing conditions known to increase liability for behavioral problems among vulnerable populations and building supportive environments are strategies consistently found to avert trajectories away from substance use in general and substance use disorders (SUD) in particular. Investments in this approach are expected to result in significantly lower rates of SUD in current and subsequent generations of youth and, therefore, will reduce the burden on our communities in terms of lowered social and health systems involvement, treatment needs, and productivity. A national strategy, based on strong scientific evidence, is presented to implement public health policies and prevention services. These strategies work by improving child development, supporting families, enhancing school experiences, and cultivating positive environmental conditions.

Epigenome-wide study of brain DNA methylation following acute opioid intoxication

BACKGROUND

Opioid abuse poses significant risk to individuals in the United States and epigenetic changes are a leading potential biomarker of opioid abuse. Current evidence, however, is mostly limited to candidate gene analysis in whole blood. To clarify the association between opioid abuse and DNA methylation, we conducted an epigenome-wide analysis of DNA methylation in brain samples of individuals who died from acute opioid intoxication and group-matched controls.

METHODS

Tissue samples were extracted from the dorsolateral prefrontal cortex of 153 deceased individuals (Mage = 35.42; 62 % male; 77 % European ancestry). The study included 72 opioid samples, 53 psychiatric controls, and 28 normal controls. The epigenome-wide analysis was implemented using the Illumina MethylationEPIC BeadChip; analyses adjusted for sociodemographic characteristics, negative control principal components, ancestry principal components, cellular composition, and surrogate variables. Horvath's epigenetic age and Levine's PhenoAge were calculated, and gene set enrichment analyses were performed.

RESULTS

Although no CpG sites survived false-discovery rate correction for multiple testing, 13 sites surpassed a relaxed significance threshold (p < 1.0 × 10-5). One of these sites was located within Netrin-1, a gene implicated in kappa opioid receptor activity. There was an association between opioid use and accelerated PhenoAge (b = 2.24, se = 1.11, p = .045). Gene set enrichment analyses revealed enrichment of differential methylation in GO and KEGG pathways broadly related to substance use.

CONCLUSIONS

Netrin-1 may be associated with opioid overdose, and future research with larger samples across stages of opioid use will elucidate the complex genomics of opioid abuse.

Identification and Characterization of Biomarkers and Their Role in Opioid Addiction by Integrated Bioinformatics Analysis

Although numerous studies have confirmed that the mechanisms of opiate addiction include genetic and epigenetic aspects, the results of such studies are inconsistent. Here, we downloaded gene expression profiling information, GSE87823, from the Gene Expression Omnibus database. Samples from males between ages 19 and 35 were selected for analysis of differentially expressed genes (DEGs). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and Gene Ontology (GO) enrichment analyses were used to analyze the pathways associated with the DEGs. We further constructed protein-protein interaction (PPI) networks using the STRING database and used 10 different calculation methods to validate the hub genes. Finally, we utilized the Basic Local Alignment Search Tool (BLAST) to identify the DEG with the highest sequence similarity in mouse and detected the change in expression of the hub genes in this animal model using RT-qPCR. We identified three key genes, ADCY9, PECAM1, and IL4. ADCY9 expression decreased in the nucleus accumbens of opioid-addicted mice compared with control mice, which was consistent with the change seen in humans. The importance and originality of this study are provided by two aspects. Firstly, we used a variety of calculation methods to obtain hub genes; secondly, we exploited homology analysis to solve the difficult challenge that addiction-related experiments cannot be carried out in patients or healthy individuals. In short, this study not only explores potential biomarkers and therapeutic targets of opioid addiction but also provides new ideas for subsequent research on opioid addiction.

Non-Opioid Treatments for Opioid Use Disorder: Rationales and Data to Date

Opioid use disorder (OUD) represents a major public health problem that affects millions of people in the USA and worldwide. The relapsing and recurring aspect of OUD, driven by lasting neurobiological adaptations at different reward centres in the brain, represents a major obstacle towards successful long-term remission from opioid use. Currently, three drugs that modulate the function of the opioidergic receptors, methadone, buprenorphine and naltrexone have been approved by the US Food and Drug Administration (FDA) to treat OUD. In this review, we discuss the limitations and challenges associated with the current maintenance and medication-assisted withdrawal strategies commonly used to treat OUD. We further explore the involvement of glutamatergic, endocannabinoid and orexin signaling systems in the development, maintenance and expression of addiction-like behaviours in animal models of opioid addiction, and as potential and novel targets to expand therapeutic options to treat OUD. Despite a growing preclinical literature highlighting the role of these potential targets in animal models of opioid addiction, clinical and translational studies for novel treatments of OUD remain limited and inconclusive. Further preclinical and clinical investigations are needed to expand the arsenal of primary treatment options and adjuncts to maximise efficacy and prevent relapse.

Escalated Oxycodone Self-Administration and Punishment: Differential Expression of Opioid Receptors and Immediate Early Genes in the Rat Dorsal Striatum and Prefrontal Cortex

Opioid use disorder (OUD) is characterized by compulsive drug taking despite adverse life consequences. Here, we sought to identify neurobiological consequences associated with the behavioral effects of contingent footshocks administered after escalation of oxycodone self-administration. To reach these goals, Sprague-Dawley rats were trained to self-administer oxycodone for 4 weeks and were then exposed to contingent electric footshocks. This paradigm helped to dichotomize rats into two distinct behavioral phenotypes: (1) those that reduce lever pressing (shock-sensitive) and (2) others that continue lever pressing (shock-resistant) for oxycodone during contingent punishment. The rats were euthanized at 2-h after the last oxycodone plus footshock session. The dorsal striata and prefrontal cortices were dissected for use in western blot and RT-qPCR analyses. All oxycodone self-administration rats showed significant decreased expression of Mu and Kappa opioid receptor proteins only in the dorsal striatum. However, expression of Delta opioid receptor protein was decreased in both brain regions. RT-qPCR analyses documented significant decreases in the expression of c-fos, fosB, fra2, junB, egr1, and egr2 mRNAs in the dorsal striatum (but not in PFC) of the shock-sensitive rats. In the PFC, junD expression was reduced in both phenotypes. However, egr3 mRNA expression was increased in the PFC of only shock-resistant rats. These results reveal that, similar to psychostimulants and alcohol, footshocks can dichotomize rats that escalated their intake of oxycodone into two distinct behavioral phenotypes. These animals also show significant differences in the mRNA expression of immediate early genes, mainly, in the dorsal striatum. The increases in PFC egr3 expression in the shock-resistant rats suggest that Egr3 might be involved in the persistence of oxycodone-associated memory under aversive conditions. This punishment-driven model may help to identify neurobiological substrates of persistent oxycodone taking and abstinence in the presence of adverse consequences.

Cocaine dependence: "Side effects" and syndrome formation within 1-12 months after first cocaine use

BACKGROUND

This project offers new epidemiological estimates for DSM-IV cocaine dependence among sub-groups of newly incident cocaine users in the United States (US), including estimated attack rates for 21 dependence-related cocaine side effect problems and experiences occurring <12 months after onset.

METHOD

In 2002-2016, US National Surveys on Drug Use and Health (NSDUH) sampled, recruited, and assessed cocaine experiences of non-institutionalized civilians. Unweighted estimates for year-pairs (2002-3,…,2015-16) are from 3488 cocaine powder-only initiates and 275 powder-then-crack initiates (all evaluated <12 months after onset). Analysis-weighted attack rate estimates are incidence proportions with 95% confidence intervals (CI), summarized via meta-analysis.

RESULTS

Evaluated <12 months after onset, meta-analysis summaries show 5% of powder-only initiates developed cocaine dependence (95% CI = 4%, 6%) versus 22% of powder-then-crack initiates (95% CI = 17%, 29%). For several cocaine side effect problems and experiences (e.g., 'loss of control' indicators) there is a statistically robust crack-associated excess risk.

CONCLUSIONS

Three interpretations of observed crack-associated excess risk are especially cogent and deserving of continued inquiry: (1) Powder-then-crack initiates start with heightened dependence risk susceptibilities (i.e., pre-dating onset); (2) Powder-using initiates become cocaine dependent and then start using crack; (3) The cocaine delivery variant of 'crack-smoking' is more toxic than powder insufflation. For powder-then-crack initiates, the cocaine dependence risk (22%) is modestly lower but statistically undifferentiable from a recently estimated risk of heroin dependence <12 months after heroin onset (30%). Clinicians can use these side effect estimates in an evidence-based diagnostic workup when patients disclose new onsets of cocaine use.

Global patterns of opioid use and dependence: harms to populations, interventions, and future action

We summarise the evidence for medicinal uses of opioids, harms related to the extramedical use of, and dependence on, these drugs, and a wide range of interventions used to address these harms. The Global Burden of Diseases, Injuries, and Risk Factors Study estimated that in 2017, 40·5 million people were dependent on opioids (95% uncertainty interval 34·3-47·9 million) and 109 500 people (105 800-113 600) died from opioid overdose. Opioid agonist treatment (OAT) can be highly effective in reducing illicit opioid use and improving multiple health and social outcomes-eg, by reducing overall mortality and key causes of death, including overdose, suicide, HIV, hepatitis C virus, and other injuries. Mathematical modelling suggests that scaling up the use of OAT and retaining people in treatment, including in prison, could avert a median of 7·7% of deaths in Kentucky, 10·7% in Kiev, and 25·9% in Tehran over 20 years (compared with no OAT), with the greater effects in Tehran and Kiev being due to reductions in HIV mortality, given the higher prevalence of HIV among people who inject drugs in those settings. Other interventions have varied evidence for effectiveness and patient acceptability, and typically affect a narrower set of outcomes than OAT does. Other effective interventions focus on preventing harm related to opioids. Despite strong evidence for the effectiveness of a range of interventions to improve the health and wellbeing of people who are dependent on opioids, coverage is low, even in high-income countries. Treatment quality might be less than desirable, and considerable harm might be caused to individuals, society, and the economy by the criminalisation of extramedical opioid use and dependence. Alternative policy frameworks are recommended that adopt an approach based on human rights and public health, do not make drug use a criminal behaviour, and seek to reduce drug-related harm at the population level.