I have been taking 50 mg of Zoloft for a month now. My dd is 6 months old. I didn't feel depressed at all. I was irritated, but I have four kids ranging in age from 6 months to 14 years, my dh and I work opposite shifts and share a car and we don't live near any family, so I chalked it up to being busy and stressed. One day while driving to a nearby town I visit at least several times a week, I forgot how to get there. I had my 6 month old with me and had to pull over because I was crying and freaking out. When I went to the doctor the next day and he suggested I was depressed, I thought he was nuts. He did an MRI to be sure it was nothing to worry about and talked me into trying Zoloft. I'm a breastfeeding counselor and he knows that work is a little stressful too, I carry a pager 24/7 and work only with moms who are limited in their resources. Zoloft has worked wonders. The only thing I have noticed is that my supply is more regulated and I think that is due to my stress level finally dropping off. My dd has not shown any signs of anything. She's an exceptionally content infant too so if it had effected her, I think it would have been very obvious. I'm also a very paranoid mom, we co-sleep and she has a stay at home sitter and daddy so I am sure if there had been any changes in her at all, one of us would have noticed.
Thomas Hales's book, A Medication Guide for Breastfeeding Moms, states "clinically relevant plasma levels in infants is remote at maternal doses less than 150 mg per day." It has a lactation risk catagory of L2, with L1 being the safest and L4 being the highest risk.
I was very against trying meds and now I have no intention of going off Zoloft until I am sure I am ready. I feel SOOOOOOOOOOOOOOO much better. I had no idea how bad I had gotten until after the medication started working. It had become normal to me. If you think you need to take something, you probably do. I wish I had sooner. Good luck.