From Scientific American:
Researchers have identified a strange side effect to a treatment for Parkinson’s disease: excessive gambling. Some patients taking medications known as dopamine agonists developed the problem within three months of starting treatment, even though they had previously gambled only occasionally or never at all. All of the patients in the new study were using dopamine agonists, compounds that mimic the behavior of the neurotransmitter in the brain, as part of their treatment regimes. The researchers report in the current issue of the Archives of Neurology that their newly-developed gambling problems cost patients upwards of $100,000 and, in the case of one patient, led to the break-up of her marriage.