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. To ease symptoms of Parkinson's, some patients take levodopa and other drugs that increase dopamine levels. 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.
"The past idea was that you need to ingest a drug that changes neurochemistry in the brain to get addicted, but we now know that just about anything we do alters the brain,"
says Timothy Fong, a psychiatrist and addiction expert at the University of California, Los Angeles.
"It makes sense that some highly rewarding behaviors, like gambling, can cause dramatic physical changes, too."