Remember, med school requires you to be at the top of your brain game. Taking any medication is going to affect you. However, depression will affect you to a much greater degree than any SSRI will. One warning. Do not overmedicate with an SSRI. They may tend to make you feel laize faire about stuff and that would be bad.
Other than that, I think you will be safe. If I had to give advice, I would try to be prescribed one with some norepi in it. Might give you the ability to focus a little more than just serotonin script would.