Parkinson's drug likely triggering gambling addiction, study finds

Patients with Parkinson's disease are about five times more likely to become problem or pathological gamblers than others, concludes a new Canadian study that offers some of the most dramatic evidence to date of the unusual link.

Almost one in 10 of the Parkinson's patients studied by psychiatrists in Calgary was found to have a gambling addiction of some sort, with the likely culprit being a type of drug prescribed to most people suffering from the condition, the researchers said.

In a paper just published in the Journal of Gambling Studies, they urge that all Parkinson's patients now be screened for possible gambling problems, and monitored through the course of their treatment.

"The problem has often been hidden and it's only when the spouse realizes they're being foreclosed upon, the house goes, [that it comes to light]," said Dr. David Crockford, lead author and a Calgary psychiatrist. "The loss can be in the hundreds of thousands. It's just a phenomenal amount."

Other research has also pointed to such a connection, and scientists theorize that the problem is caused by drugs that counter the shortage of dopamine in Parkinson's patients' brains, the main cause of their symptoms. As well as managing movement and balance, the chemical influences the pleasure and reward centres of the brain, perhaps encouraging such compulsive behaviour as gambling.

Dr. Crockford and colleagues recruited 140 Parkinson's patients aged 44 to 88 in three Alberta centres, through the University of Calgary Movement Disorders Clinic, and assessed them for gambling addiction using standard tests. They concluded that 3.6% were problem gamblers and 5.7% pathological gamblers, a more serious form of compulsion. The 9.3% total compares with a rate of about 1.6% among similarly aged people in the general population.

One leading expert in the field, though, said she is doubtful the prevalence is that high. Other research would indicate it is probably in the 3-6% range, said Dr. Valerie Voon, a Canadian psychiatrist now based at the U. S. National Institute for Neurological Disorders and Stroke in Washington.

The problem with looking at patients who have been referred to a specialist clinic like the one in Calgary is that they are more likely to be suffering from complications such as pathological gambling, she said, creating a bias in the research.

Dr. Crockford's paper, though, argues the research methodology avoided such "selection bias."

Meanwhile, separate research is showing it is the drugs, not the Parkinson's, causing problems. Recent studies by Dr. Voon and others have found a link to problem gambling in patients taking dopamine agonists for different conditions, such as shaking-leg syndrome.