Forty-one-year-old "Derrick" and 63-year-old"
George" had two things in common: both had Parkinson's disease
and both, within one to two months after starting to take a dopamine-agonist
medication, felt a strong urge to gamble.
George had gambled at casinos about four times a year, and he had never
overspent his self-allotted gambling limit. Now, he said, he felt an"
incredible compulsion" to gamble two or three times a week, even
when he "logically knew it was time to quit."
As for Derrick, he had never gambled before, but began gambling on the
Internet and lost $5,000 within a few months.
The cases of Derrick and George were reported July 11 on the Web site of
Archives of Neurology, along with those of nine other individuals who
also had Parkinson's disease and had started to show signs of pathological
gambling after taking a dopamine agonist. The report came from a group of
psychiatrists and neurologists at the Mayo Clinic. The lead author was M.
Leann Dodd, M.D., a psychiatrist and senior associate consultant in Mayo's
Department of Psychiatry and Psychology.
Dodd and her group also conducted a MEDLINE search for any mention of
Parkinson's patients engaging in pathological gambling after getting a
dopamine agonist. They found 17, they stated in their report.
Twenty-eight cases hardly constitute compelling evidence that there is a
connection between dopamine agonists and pathological gambling. Moreover, most
Parkinson's patients who take dopamine agonists do not experience the desire
to gamble excessively, Dodd told Psychiatric News. In fact, she said,
she has never heard of any other medication having been linked with
Nonetheless, she and her colleagues suspect that dopamine agonists
triggered the pathological gambling in the cases they reported and
hypothesized why this may have occurred.
For example, they were able to follow up eight of the 11 individuals they
cited, and once these individuals tapered or stopped taking a dopamine
agonist, their urge to engage in pathological gambling ceased as well.
Also, after taking dopamine agonists, six of the patients felt a strong
desire not just to gamble but also to engage to excess in other behaviors such
as eating, drinking alcohol, having sex, and making purchases. And once these
patients stopped taking the drug or took less, their urges in all of these
domains declined dramatically. One of these patients was George. He stopped
taking his dopamine agonist abruptly. Two days later, he felt his longings to
engage in such behaviors rapidly resolve. It was "like a light switch
being turned off," he said.
Two pathological gambling authorities—Suck Won Kim, M.D., a professor
of psychiatry at the University of Minnesota, and Jon Grant, M.D., an
associate professor of psychiatry there—told Psychiatric News
that they have little doubt that dopamine agonists can trigger an impulse to
gamble. Indeed, Grant said, "Those of us who treat pathological gamblers
have also seen many movement-disordered patients who report pathological
gambling onset secondary to starting dopamine agonists."
And the reason why dopamine agonists might trigger pathological gambling,
Kim explained, is that they exert their pharmacological actions not only in
the basal ganglia that govern Parkinson's symptoms, but in the nucleus
accumbens. The nucleus accumbens is known to give rise to craving and
pleasure, which in turn are mediated by dopamine. Thus, if a dopamine agonist
overly excites dopamine receptors in the nucleus accumbens, it might well"
trigger cravings to gamble and excitement when winning," Kim
But if dopamine agonists can truly ignite the urge to gamble, then why do
they awaken it in only a few patients who take them? Dodd suspects that the
answer may lie in which genetic version of dopamine receptors one has
In other words, one version of the receptors might be more receptive to
dopamine stimulation than another. In fact, Dodd said, she and her colleagues
may be "doing a genetic study looking for possible polymorphisms in the
gene that codes for the dopamine D3 receptors that may be
contributing to the way this small population of patients is responding to the
Grant believes that in addition to genetic research, functional brain
imaging could help answer an even more intriguing question: Why did the
patients who only gambled secondary to taking dopamine agonists not also
develop problems with sex, alcohol, or eating?
"Pathological Gambling Caused by Drugs Used to Treat Parkinson
Disease" can be accessed at<http://archneur.amaassn.org>
by searching on the study title. ▪