The elusive science of addiction

Markus Heilig LINKÖPING, SWEDEN – I still remember a conversation I had more than 25 years ago, when I was a young physician, just starting in my work with patients struggling with drugs and alcohol. “You know, doc,” a patient told me. “Getting drunk or taking heroin feels like being hugged by mom.” I have since heard countless variations on that theme, and I’ve found them moving and fascinating. But my training had taught me not to conduct science by anecdote. So I tucked what my patients told me in the touchy-feely part of my mind. Then I went back to the lab and the rat brains that I hoped would help me figure out how to address mental health problems. But if I had stepped back and given it some thought, it would have been pretty obvious that people with addictive disorders have strong incentives to seek whatever can make them feel like being hugged. It is important that neuroscientists start to make sense of the fact that there are, for the most part, not too many other hugs available to them. The science of social epidemiology, built on Émile Durkheim’s concept of social integration (and its opposite, social exclusion), has shown the importance of relationships, social support, and productive social interactions for mental health and addictions. The data are clear and important. But there is a problem with the research on social integration: You will be hard pressed to find in it the word “brain.” Worse, if a neuroscientist like me suggests looking at the brain to understand these social processes, or that medications targeting the brain, such as methadone or buprenorphine, should be used to help people with addiction, many people in this important field become surprisingly hostile. The problem is not quite as bad on my side of the fence. I don’t know any neuroscientists who would deny the importance of social processes in driving addiction. But once we have paid lip service to this idea, most of us go back to the lab and study addiction the way we have for decades: one brain at a time. Since the discovery of the brain’s reward systems more than a half-century ago, a canonical view of addiction has emerged: addictive drugs plug into these reward systems, activate them more intensely than natural stimuli do, and thus highjack the brain. (This is an oversimplification that ignores insights into the changing function of brain circuits over time; but it is the basis of the theory.) In terms of basic science and intellectual discovery, this line of research has been highly fruitful. Today, my colleagues can genetically modify selected brain cells to make them controllable by laser light. Others can use brain imaging to visualize and measure the activity of human brains. This type of research has yielded fascinating insights into the function of the neural machinery behind motivated behavior. And yet, despite the billions of dollars and all the hopes poured into it, we have no new treatments for patients with addictions. Some clinicians and scientists have begun to question whether researchers should be so heavily focused on the brain’s reward systems and the high that their activation by drugs can produce. As patients have known for a long time, highs are important early on, when drug use begins. But while most users get a high, only about one in five develops an addiction – and only after years of using. By the time people seek treatment for an addiction, they are no longer pursuing a high. Indeed, the highs have for the most part burned out. Their brain function has changed. Their stress- and aversion systems are out of control. The chief complaint that brings patients into my office is that, without drugs, they become anxious and suffer from depression, anxiety, and disrupted sleep. This is a very painful state to be in, and they have had years to learn that there is a quick fix: to resume their drug use, though this obviously makes things worse in the long term. The basic science on this process once nurtured hope for anti-stress addiction treatments. I, together with a large team of coworkers, spent over a decade trying to develop one. It failed miserably, as have similar approaches to every other stress-related psychiatric disorder, including depression and anxiety, for which hopes were equally high. What have we been missing? I would be foolish to claim to have the final answer; addiction is a hard disease to treat. But I think an important part of the answer is that people with addictions are very different from the mice and rats we have mostly been using in the pursuit of new treatments. And there are better ways to look at addiction than the way we have done, for the most part, in our studies: one brain at a time. Stress is indeed a critical factor in triggering relapse. But in people, the most important stressors are social. For many patients, exclusion, marginalization, poverty, and loneliness are part and parcel of the addictive process. Research is beginning to find that social exclusion drives the same brain circuits that drive drug seeking. I hope that research guided by these insights will finally result in new treatments. At a minimum, however, it should make it obvious that confrontational, repressive approaches to addictive disorders are very likely to make things worse, rather than better. And that is a neurobiological fact. The writer is is Professor and Chief at the Center for Social and Affective Neuroscience, Linköping University, Sweden. Copyright: Project Syndicate

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The elusive science of addiction