Mark Thomas is a professor of neuroscience and director of the Medical Discovery Team on Addiction. His research examines how addictive drugs alter the brain and how these changes can lead to compulsive drug use. His lab is now focusing on ways to disrupt addiction relapse.
★ Newly Hired
Dr. Groman is an Assistant Professor in the Department of Neuroscience and a member of the Medical Discovery Team on Addiction. Her work is focused on understanding why some individuals are more susceptible to developing addiction compared to others. Her lab integrates measures of decision making and reinforcement learning with neuroimaging, pharmacology, proteomics, and genomic analyses across different developmental stages in animals with the goal of identifying biomarkers of addiction risk and new targets for treating addiction.
★ Newly Hired
Alexander Herman is an Assistant Professor of Psychiatry at the University of Minnesota Medical School and member of the Medical Discovery Team on Addiction. Dr. Herman's human neuroscience lab studies neural mechanisms of decision making that are impaired in addiction and amenable to treatment with neuromodulation. His lab combines invasive and non-invasive methods including intracranial electrophysiology, direct brain stimulation, magnetoencephalography and transcranial magnetic stimulation.
★ Newly Hired
Dr. Zilverstand is an assistant professor in the Department of Psychiatry and member of the University of Minnesota's Medical Discovery Team on Addiction. Her work is focused on investigating how individual differences contribute to human drug addiction. Her research group combines the analysis of existing large-scale multimodal data sets with the acquisition of new data through a variety of techniques such as interviewing, neurocognitive testing, questionnaires and multi-modal neuroimaging. Novel computational methods are employed for linking social, demographic, neurocognitive, personality and clinical measures to the neuroimaging data, to explore the existence of neurobiological subtypes within the addicted population. The goal of this research is to develop neuroscience-derived individualized treatment for individuals who are at risk for either escalation of drug use or relapse.
★ Newly Hired
Dr. Jan Zimmermann is an Assistant Professor in the Department of Neuroscience and the Center for Magnetic Resonance Research. His lab studies how the brain represents and constructs subjective value and how that signal is used to guide decision making. The lab is particularly interested in how the brain adaptively changes its coding strategy to encode statistical regularities within a changing environment. Using electrophysiology, ultra high field MRI and computational modeling the lab tries to understand how changes in reward encoding sensitivity could relate to a propensity for drug addiction.
★ Newly Hired
Marco Pravetoni is an associate professor of Medicine at the University of Minnesota Medical School. His research interest focuses on novel and more effective treatments for substance use disorders. Dr. Pravetoni’s has developed vaccines for the treatment of heroin and prescription opioid abuse and overdose. His group is also implementing a variety of strategies to generate more effective vaccines or antibody-based therapies against drugs of abuse and other unmet medical needs such as antibiotic-resistant bacteria.
★ Newly Hired
Dr. Widge is a psychiatrist and biomedical engineer. Clinically, he provides brain stimulation treatments for mood, anxiety, and substance disorders. These include deep brain stimulation, cortical stimulation, and transcranial magnetic stimulation. His research focuses on developing these treatments further, particularly the creation of new "closed loop" devices. These devices sense brain signals in real-time and deliver energy in a planned and rational fashion, compensating for each patient's specific brain network abnormalities. Dr. Widge's laboratory prototypes new stimulation paradigms and targets in rodent models, conducts clinical trials of these new technologies, and searches for biomarkers of illness and recovery to guide next-generation therapies.
★ Newly Hired
Jocelyn Richard is an Assistant Professor in the Department of Neuroscience, investigating how external cues interact with stress and negative emotional states to drive drug and alcohol seeking, even after long periods of abstinence. By measuring the activity of neurons critical for normal reward seeking, Dr. Richard can predict how intensely rats will seek out rewards like alcohol when they are exposed to environmental cues that have been previously associated with these rewards. She aims to determine what causes these neurons to be more active when animals are especially vulnerable to relapse, such as during times of intense stress or anxiety.
★ Newly Hired
Benjamin Saunders is an assistant professor of neuroscience and member of the UMN Center for Addiction Neuroscience and Medical Discovery Team on Addiction. His research explores how drug-associated cues in the environment engage the brain to trigger drug use and relapse, with the goal of identifying biological pathways that can be targeted to prevent these behaviors.
★ Newly Hired
Steven Graves is an Assistant Professor in the Department of Pharmacology. His research is focused on the neurotoxic effects of particular psychostimulants like methamphetamine and their associations with neurodegenerative diseases.
★ Newly Hired
Sade Spencer is an assistant professor of Pharmacology and a new MDT faculty hire. The broad goal of her research is to understand the synaptic mechanisms and neurocircuitry underlying drug addiction and comorbid neuropsychiatric diseases. More specifically, her research examines specific changes in synaptic transmission during and after drug self-administration. To accomplish this goal, her lab studies neuroadaptations and behavior in rodent models of addiction using standard approaches in protein biochemistry and behavioral pharmacology as well as incorporating novel techniques to genetically isolate specific cell types and circuits implicated in addiction.
★ Newly Hired
Julia Lemos is an Assistant Professor of Neuroscience and member of the University’s Medical Discovery Team on Addiction. Her laboratory investigates how stress is processed and encoded in the brain. In particular, they interested in understanding how stress-associated neuropeptides regulate the function of neural circuits important for motivation and emotion in individuals with different life histories. Her laboratory also works to understand how chronic or traumatic stress renders the brain vulnerable to disease states such as depression, anxiety, and addiction.
★ Newly Hired
Ben Hayden is an associate professor in the Department of Neuroscience and the Center for Magnetic Resonance Research. His lab studies the role of the brain activity in making reward-based decisions, and in changing strategies in demanding circumstances. They do this with recordings of activity of populations of neurons in subjects making and adjusting simple decisions. They then compare these patterns with those obtained from subjects exposed to cocaine for long periods of times. This research contributes to a basic understanding of the brain circuitry of drug addiction.
★ Newly Hired
Sarah Heilbronner is an assistant professor in the Department of Neuroscience. She studies the "wiring diagram" of the brain. She and her team are trying to determine how different brain regions connect with one another. She is especially interested in circuits responsible for abnormal motivation and decision-making in addiction. Heilbronner uses these connectivity studies to figure out how to translate results from humans to nonhuman animal model species, and vice versa.
Dr. al’Absi is a Professor in the Department of Family Medicine and Biobehavioral Health, the Director of Duluth Global Health Research Institute. Dr. al’Absi has been leading a research program integrating basic, laboratory, and clinical methods to elucidate the mechanisms by which acute and chronic stress plays a role in addiction and relapse. An important, replicated finding from his program is the blunted hormonal stress response among smokers and other stimulant users, which manifests as enhanced basal pituitary-adrenocortical activity and decreased response to a range of stressors. This dysregulated pattern of response predicts early relapse. He is currently examining the role of endogenous opioids and cannabinoids in the blunting of the stress response in cannabis users and cigarette smokers.
Dr. Anker received his PhD in Cognitive and Biological Psychology from the University of Minnesota. As a graduate student and postdoctoral trainee, Dr. Anker’s work focused on the biological and behavioral factors that influence vulnerability to addiction and treatment response. Dr. Anker’s current work focuses on translational research that combines methods of assessing biological stress with clinical addiction treatment methods.
Alfonso Araque is a professor in the Department of Neuroscience. His research interests focus on the mechanisms, properties and physiological consequences of the communication between neurons and astrocytes. His research seeks to understand how the communication between neurons and astrocytes affects physiological and pathological aspects of brain function. While most studies on drug addiction are focused on neuronal mechanisms, his team aims to elucidate the involvement of astrocytes in behaviors associated with reward signaling and psychostimulant drugs, which may reveal astrocytes as potential targets for treatment of motivation disorders such as drug addiction.
Dr. Bart is an associate professor of Medicine at the University of Minnesota and director of the division of Addiction Medicine at Hennepin Healthcare. He is an internist and addiction medicine specialist. His areas of expertise include clinical pharmacology and the pharmacological management of opioid use disorders. His current research areas include the population pharmacokinetics of methadone, genetic influences of methadone pharmacology and treatment outcome, and improving strategies to integrate treatment of opioid use disorders into general medical settings. Dr. Bart is co-PI of NorthStar Node of the NIDA National Drug Abuse Treatment Clinical Trials Network and he is co-Director of the PEPFAR-SAMHSA funded Vietnam HIV-Addiction Technology Transfer Center.
Dr. Belgrade is a pain physician at the Minneapolis VA Health Care System and Medical Director for Pain Tele-health at the VA. He also is a staff physician at the Minnesota Head & Neck Pain Clinic. He is an associate professor in the Department of Rehabilitation Medicine and Adjunct Professor of Neurology at the University of Minnesota Medical School. He has participated in the development of national guidelines for the management of neuropathic pain and chronic pain and has published widely on a broad spectrum of pain topics. Dr. Belgrade developed the DIRE Score, a tool used internationally to help clinicians determine who is an appropriate candidate for long-term opioid prescribing for chronic pain.
Dr. Birnbaum is a Professor in the Department of Experimental and Clinical Pharmacology and Director of Graduate Studies for the ECP Graduate Program. Her research examines the pharmacokinetic variability in drug exposure and response relationships in special populations.
Dr. Camchong investigates the neurobiological basis of addiction. Using neuroimaging techniques such as fMRI, she studies the relationship between patterns of brain circuit activity and treatment outcome, and the ability of non-invasive brain stimulation methods to strengthen brain circuits that support abstinence. Her goal is to develop effective non-drug, non-invasive brain stimulation interventions that aid recovery from addiction and complement existing treatment programs.
Marilyn Carroll is a Professor in the Department of Psychiatry and Behavioral Science. Her research is focused on factors that underlie drug and food addiction, such as genetic differences, impulsivity, and hormonal influences. As Director of a recent P50 Center grant, she conducts translational research with animal and human subjects on sex differences, stimulant addiction and novel treatments. Currently, she is developing animal models of novel self-initiated and -maintained long-term treatments for addiction with the translational goal of having addicted drug users manage their treatment and recovery over long periods of time.
Wei Chen is a Professor of the Departments of Radiology. His research at the Center for Magnetic Resonance Research (CMRR) focuses on development of magnetic resonance imaging (MRI)/spectroscopy (MRS) methodologies and technologies for non-invasively studying cellular metabolism, bioenergetics, function and dysfunction of the brain and other organs, which could be valuable for addiction research.
Dr. Chen is an Assistant Professor in the Department of Neuroscience. Her research investigates the development of nerve projections that regulate reward and motivation. Miswiring of these neural circuits can negatively impact self-control and addictive behaviors. Dr. Chen’s lab utilizes a combination of molecular, genetic, and imaging approaches.
Professor and Head, Department of Neuroscience
Tim Ebner is a professor and Head of the Department of Neuroscience. His laboratory is interested in how information in the brain is represented spatially and temporally in populations of neurons during behavior.
Brenna Greenfield is a licensed clinical psychologist and assistant professor in the Department of Family Medicine and Biobehavioral Health on the Duluth Campus of the University of Minnesota Medical School. Her research focuses on substance use disorder treatment and recovery, with an emphasis on behavioral treatments such as mindfulness-based relapse prevention and motivational interviewing, mechanisms of behavior change, longitudinal health services research, and the promotion of health equity. She primarily collaborates with American Indian tribal nations.
Andrew Harris is a senior investigator at the Hennepin Healthcare Research Institute and an associate professor in Medicine and Psychology at the University of Minnesota. His research involves the use of preclinical models to study the behavioral pharmacology of addiction to nicotine, opioids, and other drugs of abuse.
Dorothy K. Hatsukami is a Professor in the Department of Psychiatry and is the Associate Director for the Masonic Cancer Center. Her research is focused on understanding tobacco addiction, testing novel tobacco cessation treatments and exploring ways to make currently marketed tobacco products less toxic, appealing and addictive.
Professor & Associate Department Head
Dr. Haskell-Luevano is the Philip S. Portoghese Endowed Chair in Chemical Neuroscience, Professor Associate Department Head in the Department of Medicinal Chemistry, and an Institute for Translational Neuroscience Scholar. Her research program focuses on the chemical biology of a variety of G protein-coupled receptors, including the opioid receptors. In her lab, projects involving the opioid receptors include the design and synthesis of novel probes and lead compounds, investigating ligand-receptor interactions, and exploring novel receptor signaling domains. By characterizing and modulating opioid receptor pharmacology, her work provides novel tools to probe pain management and advances ligand design strategies for opioid receptor based therapeutics.
Suhasa Kodandaramaiah is an Assistant Professor in the Department of Mechanical Engineering at the University of Minnesota. His laboratory focuses on engineering neurotechnologies to interface with the brain at multiple spatial and temporal scales. These include robotic tools for single cell recording and manipulation and #d printed polymer implants for large scale neural activity readout and perturbation.
Michael Kotlyar is an associate professor in the Department of Experimental and Clinical Pharmacology at the University of Minnesota College of Pharmacy. His research focuses on evaluating various aspects of tobacco dependence including assessing medications to assist in the smoking cessation attempt and assessing the role of stress on smoking behavior.
Dr. Krentzman is an Associate Professor at the University of Minnesota School of Social Work. She studies the phenomenon of addiction recovery and therefore studies recovery-oriented systems of care such as sober living houses, 12-step programs such as Alcoholics Anonymous, and recovery concepts such as spirituality and gratitude. Dr. Krentzman also designs interventions to support early recovery and prevent relapse. Her current work focuses on "Positive Peer Journaling" which uses a combination of positive psychology and behavioral activation.
Esther Krook-Magnuson is an Assistant Professor in the Department of Neuroscience. Her work focuses on brain circuitry, including the different types of neurons in the brain and their responsiveness to drugs like opioids.
Dr. Kushner is a Professor of Psychiatry who studies the association of addiction and comorbid psychiatric disorders. His current research, funded by NIAAA, focuses on developing and testing cognitive behavioral treatments that can improve the alcohol use disorder treatment outcomes for individuals with co-occurring anxiety and depressive disorders.
Anna Lee is an Assistant Professor in the Department of Pharmacology. Her research focuses on the mechanisms of alcohol and nicotine co-addiction, and the role of nicotinic acetylcholine receptors in mediating alcohol and nicotine addiction. Recent interests also include the abuse liability of electronic cigarettes, and sex differences in nicotinic receptor function.
Mark LeSage is a Senior Investigator in the Department of Medicine at the Hennepin Healthcare Research Institute, and Professor in the Department of Medicine and Adjunct Associate Professor in Psychology at the University of Minnesota. His research is primarily focused on the behavioral pharmacology of nicotine and tobacco, with a focus on using nonhuman drug self-administration and other models to address issues related to tobacco harm reduction and FDA regulation of tobacco products. He also employs nonhuman models to study the behavioral pharmacology of other drugs of abuse (cocaine, opioids) and develop immunotherapies (e.g. vaccines, antibodies) and other types of pharmacotherapies to treat drug abuse.
The misuse of and addiction to prescribed and illegally obtained opioids has caused a national crisis that affects public health and welfare. Our research is focused upon the structural and functional deficits in dendritic spines caused by neurological diseases and disorders. We found that opioids caused collapse of dendritic spines, which are the fundamental structural units for information storage and processing in the brain. The opioid-induced changes in dendritic spines may contribute to opioid addictions as well as opioid-induced cognitive deficits.
Dr. Lim is Professor and Vice Chair for Research in the Department of Psychiatry where he holds the Drs. T.J. and Ella M. Arneson Land Grant Chair in Human Behavior. Dr. Lim’s research interest is in the use of neuroimaging approaches to identify circuit abnormalities in brain disorders such as schizophrenia, traumatic brain injury and addiction and then to use these circuits as treatment targets for noninvasive neuromodulation interventions.
Dr. Luciana is a Distinguished McKnight University Professor in the Department of Psychology. Her research examines brain/behavior relationships in adults and children and the neuroplasticity of neural circuitry during development, as a function of substance use, and in the context of psychopathology. Specifically, she is interested in the neurobiology of executive functions that are mediated by the brain's prefrontal cortex, including working memory, planning, and emotional control as well as reward processing and the neural circuits that promote incentive motivation.
Robert Meisel is a professor in the Department of Neuroscience. A key question addressed by his lab is what makes some people more vulnerable than others to the addictive effects of drugs? One idea he has been testing in an animal model of addiction vulnerability is that the converging neural plasticity of behavioral experience and drug use renders the brain more susceptible to the addictive properties of drugs.
Paul Mermelstein is a professor in the Department of Neuroscience. His laboratory researches sex differences in the brain. Specifically, how sex hormones (estrogen in females, testosterone in males) alter the synaptic connections in the brain to influence motivated behaviors. He and his team have discovered that when estrogen concentrations rise in females, their vulnerability to abuse addictive drugs increases. They are seeking to determine the mechanisms by which estrogens impart vulnerability to drug addiction, and ways to circumvent these changes in brain plasticity, ultimately in hopes of improving therapeutic interventions.
Jessica Nielson is a neurobiologist and data scientist working at the intersection of computer science and psychiatry to understand the neurobiological mechanisms of mental health disorders that underlie addictive behaviors. She brings her expertise in neuroscience, big-data and precision medicine techniques to the group for data-driven discovery of clinically relevant models of addictive behaviors, with an interest in researching and developing novel therapies to treat the root causes of addiction.
Laura Palombi is an assistant professor at the College of Pharmacy in Duluth. She works with rural community members and coalitions to find community-specific solutions to the opioid crisis and to capitalize on community recovery capital. She also works closely with public health, health professions, and harm reduction professionals to increase access to naloxone.
Dr. Pham is a physician and assistant professor in the Department of Medicine and Pediatrics at the University of Minnesota Medical School. He works clinically as a hospitalist at the University of Minnesota Medical Center and as a primary care physician at the Community University Health Care Center (CUHCC). His work on academic medical education in health equity as well as with the underserved communities in the Twin Cities has led him to focus on Community-Based Participatory Research. His current research is in collaboration with the local urban American Indian community to develop a culturally-centered and family-centered approach to opioid use disorder treatment in primary care settings.
The Portoghese Research Group is focused on the design and synthesis of compounds that target opioid receptors, both as pharmacologic tools and as agents for treatment of pain. Novel concepts and approaches are employed for development of analgesics that are highly selective for different types of opioid receptors.
David Redish is a Distinguished McKnight University Professor in the Department of Neuroscience. He and his team explore the computational processes that underlie decision-making. His research addresses questions of addiction from the perspective of addiction as dysfunctions in those decision-making processes. His research interests span the neurophysiology of behavior, including computational, experimental, theoretical, and clinical approaches. His laboratory has major research efforts in theoretical explanations of the interactions of multiple decision-making systems, in the neurophysiology of the information processing in those decision-making systems, and in the clinical consequences of dysfunction in those decision-making systems. Through collaborations with other neuroscientists and psychologists translating their novel decision tasks to human populations, and clinicians testing consequences of their proposed explanations for dysfunction, Dr. Redish and his team explore the similarities and differences across species as a means of understanding addiction and its treatment.
Dr. Reznikoff practices in addiction medicine and is an addiction medicine doctor at Hennepin Healthcare. He is also an associate professor of medicine at the University of Minnesota. He maintains a clinical addiction medicine practice, while he is actively involved in public advocacy and regulatory issues surrounding controlled substances at the state and federal level, including the opioid prescribing workgroup and the governor's medical cannabis task force. He teaches on addiction medicine and opioid prescribing practices at the University of Minnesota Medical and Dental schools.
Patrick Rothwell is an Assistant Professor in the Department of Neuroscience. His research lab investigates the synaptic organization and behavioral function of basal ganglia circuits in health and disease. His interests include regulation of these circuits by endogenous opioid signaling, as well as the detrimental effects of chronic exposure to exogenous opioids, with a broad goal of reducing the abuse liability of opioid-based clinical therapies.
Mark Sanders is the Program Director of the University Imaging Centers and member of the Medical Discovery Team on Addiction Structural Circuits Center. His efforts in multimodal imaging and sample preparation will help explore large areas of the intact brain at microscopic resolution with a goal to help investigators identify biological pathways that can be targeted to prevent addictive behaviors.
Scientific Director, Center for Translational Medicine
Dr. Schumacher is the Scientific Director of the University of Minnesota’s Center for Translational Medicine and adjunct assistant professor in the Department of Experimental and Clinical Pharmacology. His research focuses on the preclinical testing and clinical translation of innovative drugs, biologics, cell therapies, and devices.
Professor & Chair
Dr. Simone is a Professor and Chair of the of Department of Diagnostic and Biological Sciences. His lab studies neural mechanisms underlying cancer pain, pain following chemotherapy, and pain associated with sickle cell disease. Studies are primarily focused on neural encoding of pain by primary afferent and spinal cord neurons, biochemical and molecular changes in DRG and spinal cord that contribute to persistent pain, and pharmacological modulation.
Linda Rinehart is a licensed clinical psychologist who specializes in assessment and treatment for individuals with substance use disorders. Dr. Rinehart's research focuses on understanding how cannabis use impacts relapse to alcohol among patients with an alcohol use disorder. She also examines how cannabis use impacts treatment outcomes for mood, anxiety, and other drug use disorders.
Dr. Specker is an Associate Professor and addiction psychiatrist in the Department of Psychiatry. She is Program Director for the Addiction Medicine Fellowship which trains physicians of all specialties in addiction and co-occurring psychiatric disorders. Her research interests include screening and brief intervention for adolescents at risk for substance use disorder and also is co-investigator on the use of neuroimaging approaches to identify circuit abnormalities in addiction. Pharmacotherapies for the treatment of cocaine use disorder has also been a focus of research.
Dr. Swanson works primarily as an Addiction Psychiatrist at the Minneapolis VA Medical Center. She is also an Assistant Professor in the Department of Psychiatry, Program Director for the Addiction Psychiatry fellowship, and VA Site Director for the University's Addiction Medicine fellowship. In terms of research, she currently serves as Lead Site Investigator in a multicenter clinical trial, entitled "Comparative Effectiveness of Two Formulations of Buprenorphine for Treating Opioid Use Disorder in Veterans (VA-BRAVE)".
Dr. Thayer is a professor of Pharmacology. His laboratory studies endocannabinoid signaling. Cannabinoids, analogs of the psychoactive ingredient in marijuana, act on receptors that are part of this system. Current studies examine the role of the endocannabinoid system in regulating synaptic transmission, neuroinflammation, and neurotoxicity.
Phu Tran is an Assistant Professor in the Department of Pediatrics. His research focuses on the role of epigenetics in long-term effects of early-life adversity on neural development. His lab has been investigating whether opioids exposure during pregnancy alters the epigenetic signatures of the infant’s cord blood stem cells and whether such change can be a determining factor for addictive behaviors in adolescence and adulthood.
Dr. Vrieze's lab investigates the etiology of addiction in humans in two ways. He partners with hundreds of investigators around the world to conduct large genetic association studies of millions of people to find genetic variants and genes that protect or predispose to addiction. The ultimate goal of this research is to identify specific biological and psychological risk factors for addiction, leading to novel therapeutics. He also partners with investigators at the Minnesota Center for Twin and Family Research to conduct longitudinal studies of the development of addiction and psychopathology. The goal is to understand the causes and consequences of addiction.
Research in the Vulchanova lab is focused on mechanisms underlying persistent pain. Our long-term goal is to contribute to the development of novel non-addictive chronic pain treatments. We are interested in elucidating the spinal circuits that mediate pain signaling, and in the discovery of novel signaling pathways involved in the development and maintenance of chronic pain. We are employing cutting-edge circuit-tracing, functional imaging, and transcriptomic approaches to investigate the organization of spinal pain circuits, and to quantify the contribution of novel signaling mediators (VGF-derived peptides) to chronic pain.
Research Associate Professor
Michael A. Walters is a Research Associate Professor in the Department of Medicinal Chemistry. He is also a director in the Institute for Therapeutics Discovery and Development (ITDD), a full-service drug discovery and development unit within the College of Pharmacy. His research focuses on the synthesis and characterization of novel compounds for the treatment of pain without the abuse liabilities associated with opioids. He is currently collaborating on the development of a compound called MMG22 (Portoghese Laboratory) which shows promise for the non-addictive treatment of cancer pain.
Professor & Head of the Department of Pharmacology
Kevin Wickman is a professor and department head of the Department of Pharmacology. His research program seeks to elucidate inhibitory signaling pathways that regulate the excitability of neurons in the reward circuitry. His team's recent efforts have shown that inhibitory G protein-dependent signaling pathways in the ventral tegmental area and prefrontal cortex normally serve to limit addiction-related behaviors evoked by administration of opioids and psychostimulants, but that the influence of these pathways is diminished with repeated drug exposure. They employ intracranial viral genetic and pharmacologic approaches, together with electrophysiological and behavioral analyses, to understand the molecular and cellular mechanisms underlying the reciprocal relationship between inhibitory signaling pathways in the reward circuitry and drugs of abuse. The premise behind their efforts is that if endogenous inhibitory signaling pathways can be strengthened to prevent their suppression by drugs of abuse, then the risk of addiction in susceptible individuals and/or relapse in recovering addicts might be reduced or prevented.