Odd drug warnings

So, while still awake late last night, DH and I were watching one of those medical shows (this one was about diagnosing a runner who's blood was turning to iron). Anyways, there was this - to me - really odd side-effect for one of the drugs advertised during the show:

compulsive gambling

Now, I don't recall the exact name of the drug being advertised, nor what it was supposed to treat. I can't tell the latter on most drug commercials. But I did find this from a quick google search.

[A specific drug is] prescribed for Parkinson’s, fibromyalgia, restless leg syndrome, depression, and sleep disorders.

[It] has been the focus of controversy since a 2003 and a 2005 study showed that [the drug] has been linked to compulsive pleasure-seeking behavior, particularly compulsive gambling, in patients who have taken it for Parkinson’s.

Actual article although I have no idea about its correctness and have thus edited out the drug name above.

I do find it odd that any drug would lead in specific to compusive gambling.