This post was originally published on August 20, 2014.
There are precious few positive things to be said about addiction, but there may be one: it does illustrate the incredible flexibility of the human brain. Neuroscientists use the term “plasticity” to refer to the brain’s ability to adapt. Usually we think of adaptation as a good thing, but no matter how one chooses to define addiction, it’s Exhibit A for just how plastic our brains really are.
Layers: Not Just Your Vacation Wardrobe
Over the decades, our understanding of addiction has evolved. But paradoxically, the more we’ve learned about addiction, the less it seems we actually know. That’s because addiction is far more complex and individualized than we once believed. Both the outdated notion of addiction as a moral weakness and the more accepted idea that it’s a heritable disease are concepts anyone can wrap their head around. Yet although it would be helpful if we could pinpoint an addiction gene, the reality is that heredity is just part of the picture. Environmental factors (think childhood trauma) also play a key role. And then there’s the question of what exactly is happening in the addicted brain itself.
Some researchers have characterized addiction as a disorder of learning, or a hijacking of the brain’s reward system. But these definitions are just different ways of looking at the problem of plasticity. Our brains actually adapt—though not, of course, in any healthy sense—to the presence of addictive drugs. These adaptations make it harder to kick the habit.
In the words of George Koob, director of the National Institute on Alcohol Abuse and Alcoholism, “Drug abuse is not just feeling good about drugs. Your brain is changed when you misuse drugs. It is changed in ways that perpetuate the problem.”
Let’s Talk Science Stuff
So it’s not simply the fact that getting high sends a spike of dopamine through your brain, as scientists in the 1980s believed; it’s that your brain responds at a structural level by changing its concentration of dopamine receptors. As Koob explains, even a single hit of a drug can initiate “a whole series of plastic changes to those receptors, to the brain cells that connect with them. The more you do it, the more it becomes ingrained and permanent.”
Permanent changes to the brain are exactly what the old fried egg PSA warned us about. But some experts believe the brain’s endless plasticity has a flip side and these harmful adaptations can be reversed, creating new, alternative neuropathways to replace the destructive ones of addiction.
“Any behavioral disorder is exactly the same: It involves learning and plasticity,” says Paul Kenny, a neurobiologist at the Icahn School of Medicine at Mount Sinai. “The problem we have with addiction is that we still don’t understand what connections in the brain are doing.”
The Brain Game
Scientists have pinpointed some common patterns that addicts’ brains share, like decreased gray matter in parts of the brain that control learning and reward processes. Even in the absence of drugs, addicts’ brains also tend towards deficits in decision-making and emotional self-awareness. But Rita Goldstein, an addiction neuroimaging researcher at Mount Sinai, cautions that “it’s always the chicken-and-egg question: Are these deficits there before addiction developed or did they develop with addiction?”
While researchers may spend decades untangling the confounding web of genetics, environment and neurological factors underlying addiction, one thing is clear: addictive substances are mind-altering in the most literal sense.