sky, taking a mulitvitiam, can help you to feel better because it may give you the vitamns and minerals you are missing from not either eating correctly (i'm on a limb) and if you do not do this taking one can help..
The best medicane for deperssion is of course talking to your p doc and your thearpist, and of course stayin on the treatment that you have been on..
I have started a new diet, and it says that exersice and mulitvatiamns can help with the deperssion only if you want to lose the wieght, and want to feel better
I hope this helps, with what you were aksing..
as for Folic acid, it is manly for pregnant woman and does not have any studies shown for depession.. I could not find any on the net
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take time to heal thyself before trying to help others, or you will never get better