Unaware of the damage

Everything usually seems easier for those who see the situation from the outside, it's true. But if the damage caused by addiction is so obvious to non-addicted friends and family members—the distortion of priorities, family breakdown, financial costs, not to mention involvement with drug trafficking when the object of addiction is illegal, and the risks of overdose and death—how is it possible for the addict to continue using?

One explanation, quite convenient for some, is that addiction is a disease. But it is not: addicts are still capable of leading reasonably normal lives—as long as they keep their brains properly supplied with the substance. Anyone who needs several doses of caffeine a day, legally available in coffee and soft drinks, would hardly be considered sick for that.

All addictive substances have in common that they overactivate the brain's reward system, which gives us pleasure and signals what is good. As excess desensitizes the system, everything that was once good ceases to be so, and thus increasingly larger doses of the drug are needed to generate sufficient well-being.

But the story doesn't end there. One of the hottest topics at the annual meeting of the Society for Neuroscience, which ended yesterday in Washington, DC, is the additional modification caused by drugs in two regions of the cortex involved in behavior control. One is the insular cortex, which becomes hyperactive in addiction. Since this part of the cortex monitors the state of the body and allows for various bodily sensations of discomfort, hyperactivation makes addicts especially sensitive to the negative sensations of withdrawal, which then dictate their behavior.

The other change, perhaps caused precisely by the hyperactive insula, is the “hijacking” of the prefrontal cortex, which becomes hypoactive. In addicts, this deficiency is associated with less concern about the long-term consequences of addiction and a lack of insight into their own condition. In other words, the brain is unaware of the damage it is causing itself—which is very convenient for its purpose of obtaining more drugs, and only prolongs the situation.

But there is hope: the addicted brain is still capable of assessing the damage caused by the addicted brain of others. And perhaps this is why group therapy, such as meetings for addicts, is so useful: using one clueless brain as an example to sensitize another clueless brain...

Excerpted from Suzana Herculano-Houzel (2025) Neuroscience of Everyday Life, originally published in Folha de São Paulo in November 2008.