I've been asked this question twice this week. I think the question is more interesting for the reason why it is being asked than for the actual answer. Even after I've explained the diagnosis and what it means, discussed my treatment recommendations and the risks and benefits of treatment, even after the patient has agreed to try the treatment, they still have to ask if the medication will work.
In prison the obvious reason why someone would ask me this is because it's a prison. Inmates inherently aren't going to trust what they're told or the people treating them. When I hear this, I know that what the patient is really saying is: "Are you telling me the truth? Or are you just giving me something to placate me and get me out of your office?" At other times they are asking this because underneath it all they worry that they may never get well. By the time I see some of these guys they have already been treated by with a list of medications the length of your arm. They may be frustrated and nihilistic about trying anything new, or anything they think they've tried before. Remoralization is the key here, to remind people that they should never give up or lose the hope of getting well. Building trust is a secondary issue, one that may not get accomplished during a single incarceration. Trust is an individual issue that is built up gradually with each patient contact. It can also be fostered (or undermined) by your reputation within the facility. My patients talk to one another, sometimes because they're celling together. The trust question is usually settled before they come to my office on that basis alone; it usually is only an issue nowadays for the guys who have never met me before.
When I am sked, "Will this medication help me?" I know the best answer I can give is, "I believe it will. I know I will do my best to help you."