Estimated probability of becoming a case of drug dependence in relation to duration of drug-taking experience: a functional analysis approach

DNA Epigenetics in Addiction Susceptibility

Addiction is a chronically relapsing neuropsychiatric disease that occurs in some, but not all, individuals who use substances of abuse. Relatively little is known about the mechanisms which contribute to individual differences in susceptibility to addiction. Neural gene expression regulation underlies the pathogenesis of addiction, which is mediated by epigenetic mechanisms, such as DNA modifications. A growing body of work has demonstrated distinct DNA epigenetic signatures in brain reward regions that may be associated with addiction susceptibility. Furthermore, factors that influence addiction susceptibility are also known to have a DNA epigenetic basis. In the present review, we discuss the notion that addiction susceptibility has an underlying DNA epigenetic basis. We focus on major phenotypes of addiction susceptibility and review evidence of cell type-specific, time dependent, and sex biased effects of drug use. We highlight the role of DNA epigenetics in these diverse processes and propose its contribution to addiction susceptibility differences. Given the prevalence and lack of effective treatments for addiction, elucidating the DNA epigenetic mechanism of addiction vulnerability may represent an expeditious approach to relieving the addiction disease burden.

Accelerated development of cocaine-associated dopamine transients and cocaine use vulnerability following traumatic stress

Post-traumatic stress disorder and cocaine use disorder are highly co-morbid psychiatric conditions. The onset of post-traumatic stress disorder generally occurs prior to the development of cocaine use disorder, and thus it appears that the development of post-traumatic stress disorder drives cocaine use vulnerability. We recently characterized a rat model of post-traumatic stress disorder with segregation of rats as susceptible and resilient based on anxiety-like behavior in the elevated plus maze and context avoidance. We paired this model with in vivo fast scan cyclic voltammetry in freely moving rats to test for differences in dopamine signaling in the nucleus accumbens core at baseline, in response to a single dose of cocaine, and in response to cocaine-paired cues. Further, we examined differences in the acquisition of cocaine self-administration across groups. Results indicate that susceptibility to traumatic stress is associated with alterations in phasic dopamine signaling architecture that increase the rate at which dopamine signals entrain to cocaine-associated cues and increase the magnitude of persistent cue-evoked dopamine signals following training. These changes in phasic dopamine signaling correspond with increases in the rate at which susceptible rats develop excessive cocaine-taking behavior. Together, our studies demonstrate that susceptibility to traumatic stress is associated with a cocaine use-vulnerable phenotype and suggests that differences in phasic dopamine signaling architecture may contribute to the process by which this vulnerability occurs.

The Molecular Basis of Drug Addiction: Linking Epigenetic to Synaptic and Circuit Mechanisms

Addiction is a disease in which, after a period of recreational use, a subset of individuals develops compulsive use that does not stop even in light of major negative consequences. Here, we review the evidence for underlying epigenetic remodeling in brain in two settings. First, excessive dopamine signaling during drug use may modulate gene expression, altering synaptic function and circuit activity and leading over time to maladaptive behaviors in vulnerable individuals. Second, on a longer timescale, life experience can shape the epigenetic landscape in brain and thereby may contribute to an individual's vulnerability by amplifying drug-induced changes in gene expression that drive the transition to addiction. We conclude by exploring how epigenetic mechanisms might serve as therapeutic targets for addiction treatments.

Personal experience and attitudes of pain medicine specialists in Israel regarding the medical use of cannabis for chronic pain

Introduction

The scientific study of the role of cannabis in pain medicine still lags far behind the growing use driven by public approval. Accumulated clinical experience is therefore an important source of knowledge. However, no study to date has targeted physicians who actually use cannabis in their daily practice.

Methods

Registered, active, board-certified pain specialists in Israel (n=79) were asked to complete a Web-based survey. The survey was developed using the Qualtrics Online Survey Software. Questions were formulated as multiple-choice questions, and these addressed three areas of interest: 1) doctors’ personal experience; 2) the role of cannabis in pain medicine; and 3) cannabis medicalization and legalization.

Results

Sixty-four percent of all practicing pain specialists in Israel responded. Almost all prescribe cannabis. Among them, 63% find cannabis moderately to highly effective, 56% have encountered mild or no side effects, and only 5% perceive it as significantly harmful. Common indications are neuropathic pain (65%), oncological pain (50%), arthralgias (25%), and any intractable pain (29%). Leading contraindications are schizophrenia (76%), pregnancy/breastfeeding (65%), and age <18 years (59%). Only 12% rated cannabis as more hazardous than opiates. On a personal note, 45% prefer cannabis for themselves or a family member. Lastly, 54% would like to see cannabis legalized in Israel.

Conclusion

In this survey, pain clinicians experienced in prescribing cannabis over prolonged periods view it as an effective and relatively safe treatment for chronic pain, based on their own experience. Their responses suggest a possible change of paradigm from using cannabis as the last resort.

Nicotine dependence predicts cannabis use disorder symptoms among adolescents and young adults

PURPOSE

We evaluate if cigarette smoking and/or nicotine dependence predicts cannabis use disorder symptoms among adolescent and young adult cannabis users and whether the relationships differ based on frequency of cannabis use.

METHODS

Data were drawn from seven annual surveys of the NSDUH to include adolescents and young adults (age 12-21) who reported using cannabis at least once in the past 30 days (n = 21,928). Cannabis use frequency trends in the association between cigarette smoking, nicotine dependence and cannabis use disorder symptoms were assessed using Varying Coefficient Models (VCM's).

RESULTS

Over half of current cannabis users also smoked cigarettes in the past 30 days (54.7% SE 0.48). Cigarette smoking in the past 30 days was associated with earlier onset of cannabis use, more frequent cannabis use and a larger number of cannabis use disorder symptoms compared to those who did not smoke cigarettes. After statistical control for socio-demographic characteristics and other substance use behaviors, nicotine dependence but not cigarette smoking quantity or frequency was positively and significantly associated with each of the cannabis use disorder symptoms as well as the total number of cannabis symptoms endorsed. Higher nicotine dependence scores were consistently associated with the cannabis use disorder symptoms across all levels of cannabis use from 1 day used (past month) to daily cannabis use, though the relationship was strongest among infrequent cannabis users.

CONCLUSION

Prevention and treatment efforts should consider cigarette smoking comorbidity when addressing the increasing proportion of the US population that uses cannabis.

Estimated probability of becoming a case of drug dependence in relation to duration of drug-taking experience: a functional analysis approach

Measured as elapsed time from first use to dependence syndrome onset, the estimated "induction interval" for cocaine is thought to be short relative to the cannabis interval, but little is known about risk of becoming dependent during first months after onset of use. Virtually all published estimates for this facet of drug dependence epidemiology are from life histories elicited years after first use. To improve estimation, we turn to new month-wise data from nationally representative samples of newly incident drug users identified via probability sampling and confidential computer-assisted self-interviews for the United States National Surveys on Drug Use and Health, 2004-2013. Standardized modules assessed first and most recent use, and dependence syndromes, for each drug subtype. A four-parameter Hill function depicts the drug dependence transition for subgroups defined by units of elapsed time from first to most recent use, with an expectation of greater cocaine dependence transitions for cocaine versus cannabis. This study's novel estimates for cocaine users one month after first use show 2-4% with cocaine dependence; 12-17% are dependent when use has persisted. Corresponding cannabis estimates are 0-1% after one month, but 10-23% when use persists. Duration or persistence of cannabis smoking beyond an initial interval of a few months of use seems to be a signal of noteworthy risk for, or co-occurrence of, rapid-onset cannabis dependence, not too distant from cocaine estimates, when we sort newly incident users into subgroups defined by elapsed time from first to most recent use. Copyright © 2016 John Wiley & Sons, Ltd.

Compulsive methamphetamine taking under punishment is associated with greater cue-induced drug seeking in rats

Methamphetamine (METH) addicts lose control over drug consumption despite suffering multiple adverse medicolegal consequences. To mimic the negative events associated with drug addiction in humans, we recently introduced a rat model of self-administration (SA) with response-contingent punishment on METH intake. These procedures allowed us to distinguish between two addiction-like phenotypes in rats, those that sustained METH taking despite negative consequences (shock-resistant, SR) and rats that significantly reduced their METH intake (shock-sensitive, SS). Here, we further developed our adverse consequence model and examined incubation of METH craving by measuring cue-induced drug seeking in SR and SS rats. Male Sprague-Dawley rats were trained to self-administer METH (0.1mg/kg/injection) or saline intravenously (i.v.) during twenty-two 9-h sessions that consisted of 3 separate 3-h sessions separated by 30min. Subsequently, rats were subjected to incremental footshocks during thirteen additional 9-h METH SA sessions performed in a fashion identical to the training phase. Cue-induced drug craving was then assessed at 2 and 21days after the footshock phase. All rats escalated their intake of METH, with both phenotypes showing similar drug taking patterns during SA training. In addition, rats that continued their METH intake despite negative consequences showed even greater cue-induced drug craving following withdrawal than the rats that reduced METH intake following negative consequences. Taken together, our adverse consequence-based model highlights the possibility of identifying rats by addiction-like phenotypes and subsequent vulnerability to relapse-like behaviors. The use of similar SA models should help in the development of better therapeutic approaches to treat different stages of METH addiction.

Cannabis Epidemiology: A Selective Review

BACKGROUND

Globally, the most widely used set of compounds among the internationally regulated drugs is cannabis.

OBJECTIVE

To review evidence from epidemiological research on cannabis, organized in relation to this field's five main rubrics: quantity, location, causes, mechanisms, and prevention/ control.

METHOD

The review covers a selection of evidence from standardized population surveys, official statistics, and governmental reports, as well as published articles and books identified via MEDLINE, Web of Science, and Google Scholar as of July 2016.

RESULTS

In relation to quantity, an estimated 3% to 5% of the world population is thought to have tried a cannabis product, with at least one fairly recent use, mainly extra-medical and outside boundaries of prescribed use. Among cannabis users in the United States, roughly one in 7-8 has engaged in medical marijuana use. In relation to location, prevalence proportions reveal important variations across countries and between subgroups within countries. Regarding causes and mechanisms of starting to use cannabis, there is no compelling integrative and replicable conceptual model or theoretical formulation. Most studies of mechanisms have focused upon a 'gateway sequence' and person-to-person diffusion, with some recent work on disability-adjusted life years. A brief review of cannabis use consequences, as well as prevention and control strategies is also provided.

CONCLUSION

At present, we know much about the frequency and occurrence of cannabis use, with too little replicable definitive evidence with respect to the other main rubrics. Given a changing regulatory environment for cannabis products, new institutions such as an independent International Cannabis Products Safety Commission may be required to produce evidence required to weigh benefits versus costs. It is not clear that governmentsponsored research will be sufficient to meet consumer demand for balanced points of view and truly definitive evidence.