Research to date shows that pathological gamblers and drug addicts share many of the same genetic predispositions for impulsivity and reward seeking. Just as substance users require increasingly strong hits to get high, compulsive gamblers pursue ever riskier ventures. Likewise, both drug addicts and problem gamblers endure symptoms of withdrawal when separated from the chemical or thrill they desire. And a few studies suggest that some people are especially vulnerable to both drug addiction and compulsive gambling because their reward circuitry is inherently under-active,which may partially explain why they seek big thrills in the first place.
Even more compelling, neuroscientists have learned that drugs and gambling alter many of the same brain circuits in similar ways. These insights come from studies of blood flow and electrical activity in people’s brains as they complete various tasks on computers that either mimic casino games or test their impulse control. In some experiments, virtual cards selected from different decks earn or lose a player money; other tasks challenge someone to respond quickly to individual images that flash on a screen but not to react to others.
Further evidence that gambling and drugs change the brain in similar ways surfaced in an amazing group of people: those with the neurodegenerative disorder Parkinson’s disease. Characterized by muscle stiffness and tremors, Parkinson’s is caused by the death of dopamine-producing neurons in a section of the midbrain. Over the decade’s researchers noticed that a remarkably high number of Parkinson’s patients between 2 and 7 percent are compulsive gamblers. Treatment for one disorder most likely contributes to another. Researchers think that in some cases the resulting chemical influx modifies the brain in a way that makes risks and rewards say, those in a game of poker more appealing and rash decisions harder to resist.
A new understanding of compulsive gambling has also helped scientists redefine addiction itself. Whereas experts used to think of addiction as dependency on a chemical, they now define it as repeatedly pursuing a rewarding experience despite serious repercussions. That experience could be the high of cocaine or heroin or the thrill of doubling one’s money at the casino.