It isn't. Everyone who takes certain drugs will have his or her brain activated ("lit up") in the same way. The puzzle of addiction is not which section of the brain is stimulated, but why some people who take alcohol and other drugs feel compelled to use them repeatedly, while others do not. Alas, no imaging technology can explain this central mystery.
That something else is going on in addiction becomes self-evident when we examine the facts. For one thing, not all addictive behaviors involve drugs. It is well-known that people with addictions can shift their behavior back and forth from drug use to non-drug compulsive activities such as shopping, gambling, even cleaning house. Such astonishing variety clearly cannot be attributed to narcotic effect or a "brain disease."
For another, even where physical addiction is present, there are no simple rules. After the Vietnam War, thousands of soldiers who had become physically dependent on heroin stopped using it once they returned home, despite the famously "addictive" nature of this drug. Once they weren't subject to the stress of war, over 90 percent of these veterans readily gave up using -- a result that cannot be explained on a neurobiological basis.
Indeed, a more modern understanding of addiction reveals an interesting fact -- most addicts feel better not when they use the drug, but when they decide to use the drug. That means there is an emotional and psychological element at play here. In fact, the critical moment of decision to perform an addictive act can occur hours or even days before the act itself. It is the emotional content of this moment that is key to understanding addiction from the inside out, and what is important in that moment is a need to remedy a sense of helplessness as I've described in a number of academic papers and my book, The Heart of Addiction (HarperCollins, 2002).
We live in a time of neurobiological reductionism in which we are repeatedly told that the mind can be reduced to the brain. Yet this will never be true. Just as chemicals that make up living things are not alive themselves, cells that make up the brain have none of the psychology that make us human. Our emotional lives come into existence only when billions of cells work together, and what they produce can not be predicted by looking at a single cell and extrapolating. As Nobel laureate Philip Anderson pointed out in a seminal paper on complex systems, "Psychology is not applied biology, nor is biology applied chemistry." Those who study brain biochemistry are doing useful work in understanding biologically-based major mental illness such as schizophrenia. But they make a mistake when they believe they are discovering something about the vast area of conflicts and emotional issues that make up the lives of the rest of us.
If we could take a more accurate image of addiction in the brain, it would encompass much of the history and many of the events that make us who we are. The intolerable helplessness that drives addiction is different for each person, but this much is known -- it is far more personal and complex than a bright spot on a screen. Until we invent a machine that can read our souls, a compassionate understanding of ourselves and talk therapy remain the most effective tools we have.
In subsequent posts on this blog I will describe the psychology that is the basis of addiction.