There are doctors and psychologists who deal with psychological addictions to behavioural ticks and compulsions, including sexual addiction. Yes, some denominations seem intent on making it a much bigger problem than it is, but that doesn't mean it does not exist.
Also, a person can get mentally (even when there is no physical addiction present) to most any substance, including viagra. It's probably pretty rare if it happens, but it could.
As for pornography... yes, again, some religious sects/denominations/orders do exagerate the "problem of pornography". For most, it's not really a big problem, just a naughty little distraction.
But there are people who get addicted to images, texts, and repetitive behaviours and movements. In mild forms, they are bad habits; in more severe forms, they are addictions. And just as a minority of people are addicted to pulling out their hair, eating or not eating or eating in certain rituals only (each of these is an illness in their own right) some have an illness that causes them to be "addicted" to certain sexual acts/behaviours/repetive movements.
In other words, some religious sects harp on it way too much. But there are real problems, dealt with by medical professionals, just a much smaller scale than many religious figures would have us believe.
And for those who have a healthy sexual appetite but have trouble with the physical aspect, there's Viagra.