I don't think employers are able to screen for gambling problems. How would they be able to do that? Waste of time and resources for them. It is not like someone steals money from the company everyday to feed their gambling addiction. They can't screen their employees, but I am pretty much sure that if they somehow gets to know about their gambling problem (even if they don't steal money from the company), they will get into trouble and likely lose their job.
Totally a waste of time because you cant know if those applicants would be telling the truth or not once you do ask them for some personal things like hobbies or any activities that they are involved with.
The way on where people could be caught up on doing gambling activities is on the time that they've been already get hired and then doing all of those things which there's someone could
make out some report but knowing previous or things in life before getting the job is impossible.Everything could really be denied if they wanted to.
I believe you, there no way an applicant will disclose this kind of information knowing that he will not be getting the position once the hiring officers know his gambling background, they will surely denied things and the only way that it can be revealed is when problem start to show up, but if there's nothing that will affect the employee's job role there's nothing that the company should held them responsibility.
It's their life, and it's outside the business, unless, again, if there's any effect with the job and the company.
Employers can quickly terminate the employee, it's part of their right when proven that there's a problem with the person involve.