N-Acetyl Cysteine for Depressive Symptoms in Bipolar Disorder-A Double-Blind Randomized Placebo-Controlled Trial. (http://www.ncbi.nlm.nih.gov/pubmed/18534556)

I dont have bipolar but I take 1200 mg of N-Acetyl Cysteine daily though. Not sure how much the study used.

http://en.wikipedia.org/wiki/Acetylcysteine#Investigational