I assume the technology for anti-depression drugs will keep improving. That seems reasonable. And I assume that being in jail would make the average person depressed. Prisons have healthcare for the inmates, and depression is a legitimate health problem. Here's the dilemma: Do you give a prisoner drugs that will make him happy despite being in jail, or do you have an obligation to keep him depressed? After all, you don't want people thinking that committing a crime will improve their happiness whether they get caught or not.
I expect some quibbling about the definition of depression. I understand there is a big difference between the debilitating form and the type where you are sad for a perfectly good reason. But if your reason for being depressed is a long prison sentence, that reason probably won't pass for years. And if you are having suicidal thoughts, that is generally considered a sign of the serious type of depression. I have to think most people with a long prison sentence entertain the thought of suicide. At what point is it ethically appropriate to treat prison-induced depression?