i've always found it very strange that things like alcohol, drug and gambling addiction are described as diseases.
it seems much more like a psychological condition to me. to cure it your need your behavior patterns restructured which is not something an operation or drug is likely to solve.
on top of that addiction implies a physical need whereas gambling is a craving or compulsion. an alcoholic or heroin addict may suffer severe physical consequences if they don't get what they're addicted to. it's not quite the same for a gambler but no doubt they're gonna be sad.
But it's a fact that some antidepressants and mood stabilizers may be effective in reducing gambling behavior. Unfortunately drugs are not effective in treating gambling addiction in around 50% of cases but surely there are some positive results. Even if it was just a placebo effect it doesn't matter because the final result is what counts. For example Lithium is one of the best mood stabilizers according to most researchers. You can find a mineral water which contains trace amounts of Lithium and drinking it can help you to overcome gambling addiction.
Of course, people are different and any particular issue should be considered on a case-by-case basis, but I'm sure that for some people just drinking water with Lithium can be helpful.
Disease and addiction are two different things and you cannot say that gambling is a disease. It is an addiction and cannot be leaved easily. On the other hand disease can be controlled easily if minor problem. Other big difference is that disease is harmful only for the patient, but gambling is evil for the whole community. It has destroyed lot of individuals and families as well.