What do drugs such as heroin do to the brain to make them so addictive? Over the past 20 years, research into drug addiction has identified several chemical and physical changes to the brain brought on by addictive substances.

There is a wad of nerve cells in the central part of your brain called the nucleus accumbens. When you eat a doughnut, have sex or do something else that your brain associates with survival and breeding, this region is inundated with dopamine. This chemical transaction is partly responsible for the experience of pleasure.

Drugs such as heroin also trigger this response, but the dopamine surge from drugs is faster and long-lasting. The brain reacts by dampening its dopamine response — not just to heroin or cocaine, but probably to all forms of pleasurable behavior. As a result, hyperstimulating drugs become the only way to trigger a palpable dopamine response.

Sights, sounds and smells associated with the drug high prime this dopamine response, and the motivation to seek the big reward of a drug hit builds. Recent research suggests that the connection between these cues and the motivation to seek a high strengthens over time in the brain of a hardened addict. Eventually, so much of his or her life become associated with getting high that it becomes nearly impossible to resist the urge.

The situation is not hopeless. Some pharmaceuticals are being studied that may help degrade transmission along the neural pathway that leads from the cue to the craving. But until there is a medical solution, it helps to replace the negative voice in an addict’s head with the supportive voices of friends and family.

— The Washington Post