Speaking at a question and answer session at the 23rd Singapore Law Review Annual Lecture, Mr Magnus said that the study concluded that gambling addiction numbers before and after the establishment of the IRs remained the same.
What the IRs did, though, was provide "just another avenue for gambling", said Mr Magnus.
He added: "The thinking is that some of these gamblers moved away from the traditional gambling areas and move into casinos."
Responding to a question on the social impact of casinos, CRA chief executive Lau Peet Meng, who was also at the event, revealed that the authorities are studying overseas models where it is compulsory for gamblers to declare how much they want to lose before they step into the casino.
Currently, patrons to the IRs here can voluntarily cap their gambling outlay.
On the call for greater transparency with regard to the number of Singaporeans entering the casinos, Mr Lau agreed that this could be looked into.