Study links hormone to addiction, risk-taking

LONDON (Reuters) - People with high levels of the hormone dopamine in the brain, and low sensitivity to it, tend to be greater risk takers and may be more prone to addictive behavior, drug abuse and gambling, a study has found.

Scientists from Denmark and Japan said they had proved in research that a need for stimulation is greater on average among those who have more of the gratification hormone, dopamine, in their brains, partly because of their lower sensitivity to it.

The study by Albert Gjedde of Copenhagen University, and published in the Proceedings of the National Academy of Sciences (PNAS) journal on Monday, scanned the brains of healthy volunteers to look at dopamine and dopamine receptor levels.

"People at the higher end of the scale get less effect from the same amount of dopamine as people lower on the scale, until they get so low in dopamine that there is too little...to have an effect," Gjedde told Reuters in an email.

The findings could help scientists develop ways to prevent or treat addictive behavior, they said, and throw new light on drug approaches to conditions like attention deficit hyperactivity disorder, commonly called ADHD.

The researchers said their findings showed people at the low and high ends of the scale have very different dopamine and dopamine receptor profiles, suggesting it may be better to try to increase or decrease levels of the dopamine itself, rather than to block the receptors.

Drugs like AstraZeneca's Seroquel and Eli Lilly's Zyprexa, which belong to a class of drugs known as antipsychotics, work by blocking the action of dopamine in the brain.

They are approved for mental illnesses such as depressions, schizophrenia and bipolar disorder but also increasingly are prescribed for children with ADHD.

(Editing by Michael Roddy)