Addiction as a brain disease revised: why it still matters, and the need for consilience

A scoping review of electroencephalographic (EEG) markers for tracking neurophysiological changes and predicting outcomes in substance use disorder treatment

Substance use disorders (SUDs) constitute a growing global health crisis, yet many limitations and challenges exist in SUD treatment research, including the lack of objective brain-based markers for tracking treatment outcomes. Electroencephalography (EEG) is a neurophysiological technique for measuring brain activity, and although much is known about EEG activity in acute and chronic substance use, knowledge regarding EEG in relation to abstinence and treatment outcomes is sparse. We performed a scoping review of longitudinal and pre-post treatment EEG studies that explored putative changes in brain function associated with abstinence and/or treatment in individuals with SUD. Following PRISMA guidelines, we identified studies published between January 2000 and March 2022 from online databases. Search keywords included EEG, addictive substances (e.g., alcohol, cocaine, methamphetamine), and treatment related terms (e.g., abstinence, relapse). Selected studies used EEG at least at one time point as a predictor of abstinence or other treatment-related outcomes; or examined pre- vs. post-SUD intervention (brain stimulation, pharmacological, behavioral) EEG effects. Studies were also rated on the risk of bias and quality using validated instruments. Forty-four studies met the inclusion criteria. More consistent findings included lower oddball P3 and higher resting beta at baseline predicting negative outcomes, and abstinence-mediated longitudinal decrease in cue-elicited P3 amplitude and resting beta power. Other findings included abstinence or treatment-related changes in late positive potential (LPP) and N2 amplitudes, as well as in delta and theta power. Existing studies were heterogeneous and limited in terms of specific substances of interest, brief times for follow-ups, and inconsistent or sparse results. Encouragingly, in this limited but maturing literature, many studies demonstrated partial associations of EEG markers with abstinence, treatment outcomes, or pre-post treatment-effects. Studies were generally of good quality in terms of risk of bias. More EEG studies are warranted to better understand abstinence- or treatment-mediated neural changes or to predict SUD treatment outcomes. Future research can benefit from prospective large-sample cohorts and the use of standardized methods such as task batteries. EEG markers elucidating the temporal dynamics of changes in brain function related to abstinence and/or treatment may enable evidence-based planning for more effective and targeted treatments, potentially pre-empting relapse or minimizing negative lifespan effects of SUD.

Effect of Voluntary Wheel-Running Exercise on the Endocrine and Inflammatory Response to Social Stress: Conditioned Rewarding Effects of Cocaine

The present paper evaluates the effect of physical activity on the increase of the conditioned rewarding effects of cocaine induced by intermittent social stress and on the neuroinflammatory response that contributes to the enhancement of drug response. For that purpose, three studies were designed in which social stress was induced in different samples of mice through a social-defeat protocol; the mice underwent an increase of physical activity by different modalities of voluntary wheel running (continuous and intermittent access). The results showed that continuous access to running wheels prior to stress enhanced the establishment of cocaine place preference, whereas an intermittent access exerted a protective effect. Wheel running contingent to cocaine administration prevented the development of conditioned preference, and if applied during the extinction of drug memories, it exerted a dual effect depending on the stress background of the animal. Our biological analysis revealed that increased sensitivity to cocaine may be related to the fact that wheel running promotes inflammation though the increase of IL-6 and BDNF levels. Together, these results highlight that physical exercise deeply impacts the organism’s response to stress and cocaine, and these effects should be taken into consideration in the design of a physical intervention.

From concepts to treatment: a dialog between a preclinical researcher and a clinician in addiction medicine

The debate surrounding the brain disease model and the associated questioning of the relevance of animal models is polarizing the field of addiction, and tends to widen the gap between preclinical research and addiction medicine. Here, we aimed at bridging this gap by establishing a dialog between a preclinical researcher and a clinician in addiction medicine. Our objective was to evaluate animal models and the neuroscientific conceptualization of addiction in light of alcohol or drug dependence and treatment in patients struggling with an addiction. We sought to determine how preclinical research influenced addiction medicine over past decades, and reciprocally, what can preclinical researchers learn from addiction medicine that could lead to more effective approaches. In this dialog, we talk about the co-evolution of addiction concepts and treatments from neuroscientific and medical perspectives. This dialog illustrates the reciprocal influences and mutual enrichment between the two disciplines and reveals that, although preclinical research might not produce new pharmacotherapies, it does shape the theoretical conceptualization of addiction and could thereby contribute to the implementation of therapeutic approaches.

Is a brain-based understanding of addiction predominant? An assessment of addiction researchers' conceptions of addiction and their evaluation of brain-based explanations

INTRODUCTION

Brain-based explanations of addiction have become a prominent explanatory model in recent decades. Although opposing views have been published, there is no large-scale study of researchers' opinions, unlike for treatment staff, the public and affected individuals. Therefore, this study aimed to examine international addiction researchers' perspectives on: (i) brain-based explanations of addiction; (ii) the perceived dominance of the concept in science, society, treatment and among those affected; and (iii) researchers' general conception of addiction in terms of ontologies and causes.

METHODS

A sample of 1440 international addiction researchers was compiled. Views were assessed online via LimeSurvey using a 'mixed methods light' approach (Likert-type scales, free-text fields). Qualitative content analyses of free-text comments complemented descriptive statistics.

RESULTS

One hundred and ninety researchers participated (13.19% response). The classification of substance use disorders as brain diseases/disorders was shared by about 60% of the respondents. Approximately 80% considered it the dominant view in science, but fewer in treatment, society and affected persons. Approximately 75% found it an oversimplification, but regarded it as helpful for understanding substance use disorders. Altogether, various biological, psychological and social factors were considered causal. Comments indicated that an over-simplistic nature of brain-based explanations of addiction was viewed as particularly problematic.

DISCUSSION AND CONCLUSIONS

A rejection of a simplistic view of addiction in favour of a multi-causal concept in which the brain plays a role seems to be the majority view of participating researchers. Therefore, the orientation of future research, treatment and support for addicted persons need to be reconsidered accordingly.

Differential association between the GLP1R gene variants and brain functional connectivity according to the severity of alcohol use

Growing evidence suggests that the glucagon-like peptide-1 (GLP-1) system is involved in mechanisms underlying alcohol seeking and consumption. Accordingly, the GLP-1 receptor (GLP-1R) has begun to be studied as a potential pharmacotherapeutic target for alcohol use disorder (AUD). The aim of this study was to investigate the association between genetic variation at the GLP-1R and brain functional connectivity, according to the severity of alcohol use. Participants were 181 individuals categorized as high-risk (n = 96) and low-risk (n = 85) alcohol use, according to their AUD identification test (AUDIT) score. Two uncommon single nucleotide polymorphisms (SNPs), rs6923761 and rs1042044, were selected a priori for this study because they encode amino-acid substitutions with putative functional consequences on GLP-1R activity. Genotype groups were based on the presence of the variant allele for each of the two GLP-1R SNPs of interest [rs6923761: AA + AG (n = 65), GG (n = 116); rs1042044: AA + AC (n = 114), CC (n = 67)]. Resting-state functional MRI data were acquired for 10 min and independent component (IC) analysis was conducted. Multivariate analyses of covariance (MANCOVA) examined the interaction between GLP-1R genotype group and AUDIT group on within- and between-network connectivity. For rs6923761, three ICs showed significant genotype × AUDIT interaction effects on within-network connectivity: two were mapped onto the anterior salience network and one was mapped onto the visuospatial network. For rs1042044, four ICs showed significant interaction effects on within-network connectivity: three were mapped onto the dorsal default mode network and one was mapped onto the basal ganglia network. For both SNPs, post-hoc analyses showed that in the group carrying the variant allele, high versus low AUDIT was associated with stronger within-network connectivity. No significant effects on between-network connectivity were found. In conclusion, genetic variation at the GLP-1R was differentially associated with brain functional connectivity in individuals with low versus high severity of alcohol use. Significant findings in the salience and default mode networks are particularly relevant, given their role in the neurobiology of AUD and addictive behaviors.

The roles of the circadian hormone melatonin in drug addiction

Given the devastating social and health consequences of drug addiction and the limitations of current treatments, a new strategy is needed. Circadian system disruptions are frequently associated with drug addiction. Correcting abnormal circadian rhythms and improving sleep quality may thus be beneficial in the treatment of patients with drug addiction. Melatonin, an essential circadian hormone that modulates the biological clock, has anti-inflammatory, analgesic, anti-depressive, and neuroprotective effects via gut microbiota regulation and epigenetic modifications. It has attracted scientists' attention as a potential solution to drug abuse. This review summarized scientific evidence on the roles of melatonin in substance use disorders at the cellular, circuitry, and system levels, and discussed its potential applications as an intervention strategy for drug addiction.

A Pilot Study on the Association of Lead, 8-Hydroxyguanine, and Malondialdehyde Levels in Opium Addicts' Blood Serum with Illicit Drug Use and Non-Addict Persons

While a large body of literature has shown the health problems of illicit drug use, research is needed on how substance abuse impacts DNA damage and contaminants in blood, especially given Pb-contaminated opium. This pilot study aimed to evaluate the levels of lead (Pb), 8-hydroxy di-guanine (8-oxo-Gua), and malondialdehyde (MDA) in the blood serum of opium addicts and non-addict people. The current study is a case–control study with a cross-sectional design. A sample of 50 opium-addicted and non-addict adults were chosen for this study using convenience and random sampling methods. Participants were divided into two groups: addicts and non-addicts. The atomic absorption spectroscopy method was used to measure the quantity of Pb, and the Enzyme-Linked Immunosorbent Assay (ELISA) method was used to measure the amount of 8-oxo-Gua and MDA. The data were analyzed using an independent t-test. The results show that the amount of Pb in the blood serum of addicted women and men was higher than levels in non-addict men and women, for the study participants (p-value = 0.001). Blood levels were not significantly different between addicts and non-addicts for men or women for 8-oxo-Gua (p-value = 0.647 for women and p-value = 0.785 for men) and MDA (p-value = 0.867 for women and p-value = 0.995 for men). In general, addicts’ blood Pb levels were found to be substantially higher than those of normal non-addict persons in this pilot study. As a result, testing for blood Pb levels in addicts may be informative in instances when symptoms are inconclusive.

A Bayesian learning model to predict the risk for cannabis use disorder

BACKGROUND

The prevalence of cannabis use disorder (CUD) has been increasing recently and is expected to increase further due to the rising trend of cannabis legalization. To help stem this public health concern, a model is needed that predicts for an adolescent or young adult cannabis user their personalized risk of developing CUD in adulthood. However, there exists no such model that is built using nationally representative longitudinal data.

METHODS

We use a novel Bayesian learning approach and data from Add Health (n = 8712), a nationally representative longitudinal study, to build logistic regression models using four different regularization priors: lasso, ridge, horseshoe, and t. The models are compared by their prediction performance on unseen data via 5-fold-cross-validation (CV). We assess model discrimination using the area under the curve (AUC) and calibration by comparing the expected (E) and observed (O) number of CUD cases. We also externally validate the final model on independent test data from Add Health (n = 570).

RESULTS

Our final model is based on lasso prior and has seven predictors: biological sex; scores on personality traits of neuroticism, openness, and conscientiousness; and measures of adverse childhood experiences, delinquency, and peer cannabis use. It has good discrimination and calibration performance as reflected by its respective AUC and E/O of 0.69 and 0.95 based on 5-fold CV and 0.71 and 1.10 on validation data.

CONCLUSION

This externally validated model may help in identifying adolescent or young adult cannabis users at high risk of developing CUD in adulthood.

Sex Disparities in Outcome of Patients with Alcohol-Related Liver Cirrhosis within the Eurotransplant Network—A Competing Risk Analysis

Alcohol use disorder (AUD) is one of the most important risk factors for the development of alcohol-related liver cirrhosis (ALC). Importantly, psychiatrists are an integral part of the interdisciplinary care for patients with AUD and ALC. The aim of the current study was to investigate whether sex influences the outcome within this group of patients. For this purpose, data of all registrations for liver transplantations due to ALC within the Eurotransplant region from 2010 to 2019 were analyzed for sex disparities using competing risk models and in-between group comparisons. Relevant sex differences in registration numbers (24.8% female) and investigated outcomes were revealed. Risk ratios for a positive outcome, i.e., transplantation (0.74), and those of adverse outcomes, i.e., removal from waiting list (1.44) and death on waiting list (1.10), indicated a relative disadvantage for female patients with ALC. Further, women listed for liver transplantations were significantly younger than their male counterparts. Notably, sex disparities found in registration and outcome parameters were independent of differences found in the prevalence of AUD and liver transplantations. Further research is necessary to identify the underlying mechanisms and establish strategies to ensure equity and utility in liver transplantations due to ALC.

The Impact of Alcohol-Induced Dysbiosis on Diseases and Disorders of the Central Nervous System

The human digestive tract contains a diverse and abundant microbiota that is important for health. Excessive alcohol use can disrupt the balance of these microbes (known as dysbiosis), leading to elevated blood endotoxin levels and systemic inflammation. Using QIAGEN Ingenuity Pathway Analysis (IPA) bioinformatics tool, we have confirmed that peripheral endotoxin (lipopolysaccharide) mediates various cytokines to enhance the neuroinflammation signaling pathway. The literature has identified alcohol-mediated neuroinflammation as a possible risk factor for the onset and progression of neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD), and psychiatric disorders such as addiction to alcohol and other drugs. In this review, we discuss alcohol-use-induced dysbiosis in the gut and other body parts as a causal factor in the progression of Central Nervous System (CNS) diseases including neurodegenerative disease and possibly alcohol use disorder.

Warum die Sucht eine Erkrankung des Gehirns ist

Die Ansicht, dass es sich bei Drogenabhängigkeit um eine Erkrankung des Gehirns handelt, ist in den letzten Jahren auf verschiedene Kritik gestoßen. So wurde ein dysregulierter Substanzkonsum als selbstverschuldeter Zustand wahrgenommen und die Sichtweise einer Gehirnerkrankung als deterministisch gewertet. Mit dieser Kritik setzten sich Heilig et al. nun auseinander und plädieren für die Anerkennung der Sucht als Gehirnerkrankung.

Logical fallacies and misinterpretations that hinder progress in translational addiction neuroscience

Substance use disorders (SUDs) are heterogeneous and complex, making the development of translationally predictive rodent and nonhuman primate models to uncover their neurobehavioral underpinnings difficult. Neuroscience-focused outcomes have become highly prevalent, and with this, the notion that SUDs are disorders of the brain embraced as a dominant theoretical orientation to understand SUD etiology and treatment. These efforts, however, have led to few efficacious pharmacotherapies, and in some cases (as with cocaine or methamphetamine), no pharmacotherapies have translated from preclinical models for clinical use. In this theoretical commentary, we first describe the development of animal models of substance use behaviors from a historical perspective. We then define and discuss three logical fallacies including 1) circular explanation, 2) affirming the consequent, and 3) reification that can apply to developed models. We then provide three case examples in which conceptual or logical issues exist in common methods (i.e., behavioral economic demand, escalation, and reinstatement). Alternative strategies to refocus behavioral models are suggested for the field to better bridge the translational divide between animal models, the clinical condition of SUDs, and current and future regulatory pathways for intervention development.

Is addiction a brain disease? A plea for agnosticism and heterogeneity

RATIONALE

Although increasingly subject to criticism, the brain disease model of addiction (BDMA) remains dominant within addiction science. Yet few advocates or critics of the BDMA have provided an account of what a brain disease is. The aim of this review is to conceptually clarify what it would mean for the BDMA to be true, rather than to argue decisively for or against it.

OBJECTIVES

Conceptual clarification of the BDMA requires consideration of possible models of disease and their relationship to the BDMA. A barrier to such consideration is belief that the BDMA is necessary to combatting addiction stigma. To address this barrier, I begin with discussion of what we know about the effects of the brain disease label on addiction stigma, and why labelling effects should have no bearing on the validity of the BDMA. I then distinguish strong, minimal, network, and mismatch models of disease, and I argue that the BDMA aligns with a strong disease model. This means that underlying brain pathology is hypothesized to be the cause of the personal-level observable signs and experienced symptoms characteristic of addiction. Evaluation of the BDMA therefore requires analysis of the concepts of brain dysfunction and causation, and their application to addiction science.

RESULTS

Brain dysfunction cannot be analyzed merely as brain changes or brain differences; nor can it be inferred merely from the presence of personal-level signs and symptoms. It is necessary to have an account of normal brain function by which to measure it. The theoretical and empirical challenges to developing such an account are not insurmountable, but they are substantial. Although there exist competing analyses of causation, there is a relatively standard method used to establish it within experimental science: intervention. Using this method, the causal significance of brain states, such as, e.g., extensive gray matter loss and/or neuroadapations in the mesocorticolimbic dopamine system, is not yet fully demonstrated. Further studies are necessary to determine their effect compared with other possible variables, such as, e.g., alternative reinforcers.

CONCLUSIONS

Conceptual clarification and preliminary empirical assessment of the BDMA recommends agnosticism about its validity and an openness to heterogeneity; in some cases addiction may be a brain disease, in others not. Either way, addiction stigma can be combatted by fighting moralism about drugs and moralistic drug policies directly, as opposed to resting hopes on the brain disease label.

Spiritual Addiction: Searching for Love in a Coldly Indifferent World

I describe “spiritual” addiction as a felt compulsion to seek surrogates in the absence of that spirit of unconditional love underlying core personality change. We awaken to a “real” world akin to a prison in which all sides seem morally compromised, so any choice seems to necessitate sacrificing our conscientious relationship to the truth. Thus, spiritual addiction runs deeper than physical and psychological addictions to include socially accepted “addictions” to all we associate with “success”—including our morality and religion. All that we seek may be grounded in a collectively imbibed prejudice toward truth itself. If so, such a prejudice, underlying spiritual addiction, compromises our will, reason, feelings, actions, and character—including all of our relationships. It underlies the reality of a collective moral crisis which, we show, is more deeply a religious crisis tempting us to doubt the reality and attainability of that unconditional love that provides a foundation for hope. To overcome the prejudice underlying spiritual addiction, we show how unconditional love can be realized by placing conscientiousness in the foreground of concern as we are guided by the most reliable moral and spiritual witnesses in our history distinct from any religious group claiming to speak in their name.

Internet Addiction and Its Associated Factors Among African High School and University Students: Systematic Review and Meta-Analysis

Introduction

Internet addiction is characterized by excessive and uncontrolled use of the internet affecting everyday life. Adolescents are the primary risk group for internet addiction. Data on internet addiction is lacking in Africa. Thus, this review aimed to determine the pooled prevalence of internet addiction and its associated factors among high school and university students in Africa.

Methods

A comprehensive literature search was conducted using electronic databases (PubMed/MEDLINE, Web of science, Hinari, and Google scholar) to locate potential studies. Heterogeneity between studies was checked using Cochrane Q test statistics and I2 test statistics and small-study effects were checked using Egger's statistical test at a 5% significance level. A sensitivity analysis was performed. A random-effects model was employed to estimate the pooled prevalence and associated factors of internet addiction among students. The primary outcome of measure of this review was the prevalence of internet addiction and the secondary outcome of measures are the factors associated with internet addiction.

Results

A total of 5,562 studies were identified among the five databases. Of these, 28 studies from 10 countries with 14,946 high school and university students were included in this review. The overall pooled prevalence of internet addiction among the students was 34.53% [95% Confidence Interval (CI): 26.83, 42.23, I2 = 99.20%]. Male sex [Pooled Odds Ratio (POR) = 1.92, 95% CI:1.43, 2.57 I2 = 0.00], urban residence (POR = 2.32, 95% CI:1.19, 4.53, I2 = 59.39%), and duration of daily internet use for more than 4 h (POR = 2.25, 95% CI:1.20, 4.21, I2 = 0.00%, were significantly associated with internet addiction among adolescents.

Conclusion

Almost one-third of university and high school students in Africa are addicted to the internet. Male students, those from urban areas, and those who use the internet for more than 4 h per day have higher odds of internet addiction. Thus, we recommend that health planners and policymakers pay attention to the use of the internet and internet addiction in Africa.

Pattern of predictive features of continued cannabis use in patients with recent-onset psychosis and clinical high-risk for psychosis

Continued cannabis use (CCu) is an important predictor for poor long-term outcomes in psychosis and clinically high-risk patients, but no generalizable model has hitherto been tested for its ability to predict CCu in these vulnerable patient groups. In the current study, we investigated how structured clinical and cognitive assessments and structural magnetic resonance imaging (sMRI) contributed to the prediction of CCu in a group of 109 patients with recent-onset psychosis (ROP). We tested the generalizability of our predictors in 73 patients at clinical high-risk for psychosis (CHR). Here, CCu was defined as any cannabis consumption between baseline and 9-month follow-up, as assessed in structured interviews. All patients reported lifetime cannabis use at baseline. Data from clinical assessment alone correctly classified 73% (p < 0.001) of ROP and 59 % of CHR patients. The classifications of CCu based on sMRI and cognition were non-significant (ps > 0.093), and their addition to the interview-based predictor via stacking did not improve prediction significantly, either in the ROP or CHR groups (ps > 0.065). Lower functioning, specific substance use patterns, urbanicity and a lack of other coping strategies contributed reliably to the prediction of CCu and might thus represent important factors for guiding preventative efforts. Our results suggest that it may be possible to identify by clinical measures those psychosis-spectrum patients at high risk for CCu, potentially allowing to improve clinical care through targeted interventions. However, our model needs further testing in larger samples including more diverse clinical populations before being transferred into clinical practice.

Acute effects of alcohol on social and personal decision making

Social drinking is common, but it is unclear how moderate levels of alcohol influence decision making. Most prior studies have focused on adverse long-term effects on cognitive and executive function in people with alcohol use disorders (AUD). Some studies have investigated the acute effects of alcohol on decision making in healthy people, but have predominantly used small samples and focused on a narrow selection of tasks related to personal decision making, e.g., delay or probability discounting. Here, we conducted a large (n = 264), preregistered randomized placebo-controlled study (RCT) using a parallel group design, to systematically assess the acute effects of alcohol on measures of decision making in both personal and social domains. We found a robust effect of a 0.6 g/kg dose of alcohol on both moral judgment and altruistic behavior, but no effects on several measures of risk taking or waiting impulsivity. These findings suggest that alcohol at low to moderate doses selectively moderates decision making in the social domain, and promotes utilitarian decisions over those dictated by rule-based ethical principles (deontological). This is consistent with existing theory that emphasizes the dual roles of shortsighted information processing and salient social cues in shaping decisions made under the influence of alcohol. A better understanding of these effects is important to understand altered social functioning during alcohol intoxication.

From a systems view to spotting a hidden island: A narrative review implicating insula function in alcoholism

Excessive use of alcohol promotes the development of alcohol addiction, but the understanding of how alcohol-induced brain alterations lead to addiction remains limited. To further this understanding, we adopted an unbiased discovery strategy based on the principles of systems medicine. We used functional magnetic resonance imaging data from patients and animal models of alcohol addiction-like behaviors, and developed mathematical models of the 'relapse-prone' network states to identify brain sites and functional networks that can be selectively targeted by therapeutic interventions. Our systems level, non-local, and largely unbiased analyses converged on a few well-defined brain regions, with the insula emerging as one of the most consistent finding across studies. In proof-of-concept experiments we were able to demonstrate that it is possible to guide network dynamics towards increased resilience in animals but an initial translation into a clinical trial targeting the insula failed. Here, in a narrative review, we summarize the key experiments, methodological developments and knowledge gained from this completed round of a discovery cycle moving from identification of 'relapse-prone' network states in humans and animals to target validation and intervention trial. Future concerted efforts are necessary to gain a deeper understanding of insula function a in a state-dependent, circuit-specific and cell population perspective, and to develop the means for insula-directed interventions, before therapeutic targeting of this structure may become possible.

Insights from system dynamics applications in addiction research: A scoping review

BACKGROUND AND AIMS

Substance misuse and use disorders are dynamic and complex problems, situated within systems of interacting social, environmental, and neurobiological factors. System dynamics (SD) methods broaden, test, and improve understanding of complex systems and can help inform effective action. We sought to systematically review the use of SD tools in addiction-related research.

METHODS

Following PRISMA guidelines, we searched several databases from 1958 to 2019. We included studies focused on addiction-related screening and diagnosis, treatment, and return to use, as well as studies focused on earlier stages that may begin a path to addiction (e.g., experimentation, misuse onset).

RESULTS

We extracted information from 59 articles with a median publication year of 2014. In addition to using SD to understand the underlying complexity driving addiction-related trends, other commonly cited reasons for use of SD included assessing impacts of potential actions (n = 35), predicting future trends (n = 28), and supporting strategic planning processes (n = 22). Most studies included simulation models (n = 43); however, some presented insights from qualitative SD diagrams (n = 9) and concept models (n = 6). The majority of studies focused on stages leading to potential addiction: initiation/ experimentation (n = 42) and misuse onset (n = 38). One-third (n = 20) engaged persons with lived experience or other stakeholders during the modeling process.

CONCLUSIONS

Addiction-related SD research has increased over the last few decades with applications varying in several ways, from model purpose and types of data used to stakeholder involvement. Future applications should consider the benefits of stakeholder engagement throughout the modeling process and expanding models to include concomitant substance use.

Contextual extinction of drug-associated discriminative stimuli fails to attenuate drug-vs-food choice in rhesus monkeys

Relapse within the context of a substance use disorder can be triggered by cues that function as discriminative stimuli to signal contingencies of drug availability and promote drug-taking behavior. Extinction procedures can weaken this association between drug-associated cues and drug-taking behavior and may reduce the probability of relapse. This study evaluated a regimen of extinction training on cocaine and heroin self-administration in rhesus monkeys under a drug-vs-food choice procedure. Behavior was initially maintained under a concurrent schedule of food (1-g food pellets; fixed-ratio 100 schedule) and cocaine injections (0-0.1 mg/kg/injection; fixed-ratio 10) (n = 4 males) or heroin injections (0-0.01 mg/kg/injection; fixed-ratio 10) (n = 3 females and 1 male) during daily 2-hr choice sessions. Subsequently, choice sessions were supplemented by daily 20-hr saline self-administration sessions for 14 consecutive days. During saline self-administration sessions, only drug-associated discriminative stimuli were presented and responding produced saline injections. Drug continued to be available during choice sessions. Prior to extinction training, both cocaine and heroin maintained dose-dependent increases in drug-vs-food choice. Exposure to 14 saline self-administration sessions failed to significantly decrease drug choice and increase food choice. These preclinical results do not support the effectiveness of extinguishing drug-associated discriminative stimuli as a nonpharmacological treatment strategy for reducing drug choice.

The Utility of Research Domain Criteria in Diagnosis and Management of Dual Disorders: A Mini-Review

The Research Domain Criteria (RDoC) initiative has been considered a comprehensive alternative classification framework for understanding neuropsychiatric ailments, as opposed to the longstanding, traditional DSM framework. Where the DSM categorizes neuropsychiatric disorders as each being distinct and diagnostically defined by the presence of specified symptoms, RDoC provides a multidimensional conceptualization of psychiatric disorders with neurobiological roots. By taking a multidimensional approach, RDoC overcomes two major constraints of the DSM framework: that is, that the DSM is categorical in its approach to psychiatric disorders to the point of understating the intersectionality between concomitant disorders, and that the DSM focuses mainly on clinical features. RDoC seems to better account for the intersection between dual disorders and considers a range of factors, from the more microscopic (e.g., genetics or molecular functions) to the more macroscopic (e.g., environmental influences). The multidimensional approach of RDoC is particularly appealing in the context of dual disorders. Dual disorders refers to a concurrent psychiatric disorder with an addiction disorder. RDoC accounts for the fact that there is often overlap in symptoms across and bidirectional influence between various disorders. However, to date, there is limited research into the clinical utility of RDoC, and less so in the context of the clinical management of dual disorders. In this Mini-Review, we discuss how RDoC differs from the DSM, what outcomes have been reported in utilizing RDoC clinically, the utility of RDoC for the diagnosis, management, and monitoring of psychopathology, and the limitations of RDoC as well as avenues for future research.

Differences between users' and addiction medicine experts' harm and benefit assessments of licit and illicit psychoactive drugs: Input for psychoeducation and legalization/restriction debates

BACKGROUND

There is a lack of benefit/harm assessments of illicit and licit psychoactive substances performed by substance-dependent users in comparison to addiction medicine experts.

METHODS

We extended the analyses of substance harm/benefit assessments of German addiction medicine experts (N = 101), in parts reported recently in this journal [doi.org/10.3389/fpsyt.2020.59219], by the perspectives of substance-addicted persons. The same questionnaire as used for the abovementioned "experts-study" was handed out to inpatient detoxification or rehab treatment seeking German substance-dependent adults (N = 117) for a subsequent structured interview about harms and benefits of 33 new and traditional psychoactive substances comprising also prescription drugs.

RESULTS AND DISCUSSION

Both, users and experts, ranked the traditional illicit psychoactive substances heroin, cocaine and amphetamines within the top overall harm level group. Synthetic cannabinoids, alcohol and benzodiazepine were in a subordinate top-harm level position. Both cohorts also ranked methadone, nicotine and cannabis within the midrange and buprenorphine as well as psychotropic mushrooms within the lowest harm level positions. Experiences with prescription drugs (including opioidergic analgesics and gabapentinoids), cathinones, GHB, methamphetamine and methylphenidate was not prevalent in our user population. The same applied to barbiturates, propofol, kratom, ayahuasca with nearly zero assessments for each substance. The most user-experiences (>50% per assessed substance) were reported with nicotine, cannabis, alcohol, cocaine, heroin, amphetamine and methadone (core group). The user's overall harm ratings in terms of these psychoactive substances were similar to those of the experts with the exception of the methadone assessment which was rated by the experts to be significantly less harmful if compared with the users' estimation (supposed "treatment bias" of experts). The users' benefit ratings for the traditional illicit psychoactive substances, cannabis as well as for nicotine were significantly more positive in comparison to those of the experts (supposed "attraction bias" of users). Both, experts and users, ranked the harms arising from the use of alcohol or benzodiazepines (usually unregulated substances) higher than the harms caused by the use of methadone, cannabis or psychotropic mushrooms (regulated by most Western narcotic acts). Users attributed the most benefits to buprenorphine, methadone and cannabis. This might reflect a main limitation of the study as the data are from an user population comprising over 50% patients who sought detoxification-treatment of opiates where methadone and buprenorphine are usual transient medications (supposed "selection bias").

CONCLUSION

This study addressed current trends of psychoactive substance abuse (e.g., synthetic cannabinoids, prescription drugs) and provides from both perspectives (that of the user and that of the addiction medicine experts) robust harm/benefit evaluations at least of a core group of psychoactive substances (traditional illicit psychoactive substances, cannabis, methadone, alcohol and nicotine). The results of this study can be valuable to the psychoeducation of substance-addicted individuals and to current restriction/legalization debates, especially in the Western-EU.

The protective effect of operant social reward on cocaine self-administration, choice, and relapse is dependent on delay and effort for the social reward

Social reinforcement-based treatments are effective for many, but not all, people with addictions to drugs. We recently developed an operant rat model that mimics features of one such treatment, the community-reinforcement approach. In this model, rats uniformly choose social interaction over methamphetamine or heroin. Abstinence induced by social preference protects against the incubation of drug-seeking that would emerge during forced abstinence. Here, we determined whether these findings generalize to cocaine and whether delaying or increasing effort for social interaction could reveal possibly human-relevant individual differences in responsiveness. We trained male and female rats for social self-administration (6 days) and then for cocaine self-administration, initially for 2-h/day for 4 days, and then for 12-h/day continuously or intermittently for 8 days. We assessed relapse to cocaine seeking after 1 and 15 days. Between tests, the rats underwent either forced abstinence or social-choice-induced abstinence. After establishing stable social preference, we manipulated the delay for both rewards or for social reward alone, or the response requirements (effort) for social reward. Independent of cocaine-access conditions and sex, operant social interaction inhibited cocaine self-administration and prevented incubation of cocaine seeking. Preference for social access was decreased by the delay of both rewards or social reward alone, or by increased response requirements for social reward, with notable individual variability. This choice procedure can identify mechanisms of individual differences in an animal model of cocaine use and could thereby help screen medications for people who are relatively unresponsive to treatments based on rewarding social interaction.

Environmental influence on the preclinical evaluation of substance use disorder therapeutics

Substance use disorders (SUD) develop as a result of complex interactions between the environment, the subject, and the drug of abuse. Preclinical basic research investigating each of these tripartite components of SUD individually has resulted in advancements in our fundamental knowledge regarding the progression from drug abuse to SUD and severe drug addiction and the underlying behavioral and neurobiological mechanisms. How these complex interactions between the environment, the subject, and the drug of abuse impact the effectiveness of candidate or clinically used medications for SUD has not been as extensively investigated. The focus of this chapter will address the current state of our knowledge how these environmental, subject, and pharmacological variables have been shown to impact candidate or clinical SUD medication evaluation in preclinical research using drug self-administration procedures as the primary dependent measure. The results discussed in this chapter highlight the importance of considering environmental variables such as the schedule of reinforcement, concurrent availability of alternative nondrug reinforcers, and experimental housing conditions in the context of SUD therapeutic evaluation. The thesis of this chapter is that improved understanding of environmental variables in the context of SUD research will facilitate the utility of preclinical drug self-administration studies in the evaluation and development of candidate SUD therapeutics.

Dose-Response Relationships between Levels of Alcohol Use and Risks of Mortality or Disease, for All People, by Age, Sex, and Specific Risk Factors

Alcohol use has been causally linked to more than 200 disease and injury conditions, as defined by three-digit ICD-10 codes. The understanding of how alcohol use is related to these conditions is essential to public health and policy research. Accordingly, this study presents a narrative review of different dose-response relationships for alcohol use. Relative-risk (RR) functions were obtained from various comparative risk assessments. Two main dimensions of alcohol consumption are used to assess disease and injury risk: (1) volume of consumption, and (2) patterns of drinking, operationalized via frequency of heavy drinking occasions. Lifetime abstention was used as the reference group. Most dose-response relationships between alcohol and outcomes are monotonic, but for diabetes type 2 and ischemic diseases, there are indications of a curvilinear relationship, where light to moderate drinking is associated with lower risk compared with not drinking (i.e., RR < 1). In general, women experience a greater increase in RR per gram of alcohol consumed than men. The RR per gram of alcohol consumed was lower for people of older ages. RRs indicated that alcohol use may interact synergistically with other risk factors, in particular with socioeconomic status and other behavioural risk factors, such as smoking, obesity, or physical inactivity. The literature on the impact of genetic constitution on dose-response curves is underdeveloped, but certain genetic variants are linked to an increased RR per gram of alcohol consumed for some diseases. When developing alcohol policy measures, including low-risk drinking guidelines, dose-response relationships must be taken into consideration.

Determining the sex-specific distributions of average daily alcohol consumption using cluster analysis: is there a separate distribution for people with alcohol dependence?

BACKGROUND

It remains unclear whether alcohol use disorders (AUDs) can be characterized by specific levels of average daily alcohol consumption. The aim of the current study was to model the distributions of average daily alcohol consumption among those who consume alcohol and those with alcohol dependence, the most severe AUD, using various clustering techniques.

METHODS

Data from Wave 1 and Wave 2 of the National Epidemiologic Survey on Alcohol and Related Conditions were used in the current analyses. Clustering algorithms were applied in order to group a set of data points that represent the average daily amount of alcohol consumed. Gaussian Mixture Models (GMMs) were then used to estimate the likelihood of a data point belonging to one of the mixture distributions. Individuals were assigned to the clusters which had the highest posterior probabilities from the GMMs, and their treatment utilization rate was examined for each of the clusters.

RESULTS

Modeling alcohol consumption via clustering techniques was feasible. The clusters identified did not point to alcohol dependence as a separate cluster characterized by a higher level of alcohol consumption. Among both females and males with alcohol dependence, daily alcohol consumption was relatively low.

CONCLUSIONS

Overall, we found little evidence for clusters of people with the same drinking distribution, which could be characterized as clinically relevant for people with alcohol use disorders as currently defined.

The "black box" of treatment: Patients' perspective on what works in opioid maintenance treatment for opioid dependence

BACKGROUND

A lack of conceptual modeling of how the components of opioid maintenance treatment (OMT) for opioid dependence (OD) work causes it to occasionally be labeled the "black-box" of treatment. This study had a two-fold objective: First, to analyze which factors related to OMT for OD contribute to the abstinence of problematic use of non-prescribed opioids and sustain recovery, from the patients' perspective; second, to understand which changes OMT produced in the individuals' lives might significantly contribute to relapse prevention.

METHODS

We used qualitative methods of design, inquiry, and analysis from a convenience sample of 19 individuals in a Swedish treatment setting.

RESULTS

All the participants reported previous cycles of problematic use of non-prescribed opioids and other non-prescribed psychoactive substances, treatment, abstinence, recovery, and relapse before starting the current OMT program. During the pre-treatment stage, specific events, internal processes, and social environments enhanced motivation toward abstinence and seeking treatment. During the treatment stage, participants perceived the quality of the human relationships established with primary social groups as important as medication and the individual plan of care in sustaining recovery. From the participants' perspective, OMT was a turning point in their life course, allowing them a sense of self-fulfillment and the reconstruction of personal and social identity. However, they still struggled with the stigmatization produced by a society that values abstinence-oriented over medication-assisted treatments.

CONCLUSION

OMT is not an isolated event in individuals' lives but rather a process occurring within a specific social context. Structural factors and the sense of acceptance and belonging are essential in supporting the transformation. Treatment achievements and the risk for relapse vary over time, so the objectives of the treatment plan must account for characteristics of the pre-treatment stage and the availability and capacity of individuals to restructure their social network, besides the opioid maintenance treatment and institutional social care.

Estimating the economic consequences of substance use and substance use disorders

INTRODUCTION

This contribution gives an overview on estimating the economic impact of substance use (SU) and substance use disorders (SUDs) from a societal perspective.

AREAS COVERED

In this Expert Review, we first discuss the scope of the economic costs of SU to society and the methods used to estimate them. In general, cost studies should not be limited to SUDs, but should also include costs related to the consequences of any type of SU to achieve a comprehensive picture of the societal burden. Further, estimating potentially avoidable costs will increase the value of cost studies. Importantly, methodologically sound cost studies shed light on the magnitude of societal problems related to SU and can be used as a reference point to evaluate regulatory policies and other preventive measures. The area of estimating potential economic benefits of SU is understudied and lacks a theoretical and methodological framework.

EXPERT OPINION

Overall, economic studies on the impact of SU and SUDs can strongly contribute to better-informed decision-making in the creation of regulatory and control policies. The least developed area of research refers to a consensus methodology that could be used in studies which compare economic costs to potential economic benefits.