Happiness Run Amok

Why would we ask UAB’s expert in nicotine neurobiology to speak about the biology of happiness? Because, as counterintuitive as it sounds, happiness—as far as you want to define it neurobiologically—and addiction have a lot in common.

The structures and chemical signals that make up the reward pathway in the brain are central to both positive affect (the scientist’s term for happiness) and addiction. Too much stimulation of that pathway can take a brain from feelings of happiness to cravings for what makes it happy, be that gambling, alcohol abuse, or addiction to nicotine.

Nicotine interacts with the reward system in a very powerful way, says Lester. “When it initially stimulates that pathway, it’s very rewarding or pleasurable. And when this system is stimulated, it will tend to be associated with repeated desire for that behavior,” particularly in brains that are genetically predisposed to nicotine addiction. As the system is exposed to nicotine over time, it becomes altered so it is actually dependent on nicotine. “If it doesn’t get nicotine, it’ll keep sending out signals saying, ‘Where is my nicotine?’” Lester says.

Is that to say that smokers’ brains are happy when they get nicotine? “That’s more of a philosophical question,” says Lester. “Do I now get pleasure from the nicotine or am I just returning myself to a normal state? I think the latter. Most smokers do derive some pleasure, but is it because now they’re just putting themselves back to normal, relieving a craving, rather than getting real pleasure from it.”

Lester’s lab focuses on understanding the brain mechanisms that are responsible for relapse. “Craving and subsequent relapse is one of the biggest hurdles in combating drug addiction, even after long periods of abstinence,” he says. “So one of the central goals in my lab is to look for persistent or even permanent changes in brain function after periods of drug exposure—nicotine, in this case.”

Lester says that some drugs are more viscerally linked to the pleasure pathway than others. “Many people in my field make the distinction between dependence and addiction. Our brains can become dependent on a number of different pharmaceutical medications, but people don’t tend to abuse all of those drugs. So there has to be something more. We think the ‘something more’ is a strong stimulation of this particular reward pathway. Drugs that do that, such as alcohol, nicotine, heroin, cocaine, and valium, are the substances that are most often abused.”

— Kathleen Yount