I have never heard of anyone recommending this. My concerns are twofold: I don't believe that marijuana has useful effects on depression (if it does, I have never heard of them), and I don't think it's particularly safe to care for an infant while using psychedelic drugs.
I agree with MeepyCat. I would also be concerned that IME marijuana use can increase anxiety and paranoid thoughts. Good luck in your journey to feel better.
SWIM has used cannabis to treat regular depression before, and I would assume it would have similar effects for PPD. Magnesium supplements also have anecdotal evidence to help.
Do you know any doctors who would be open to prescribing it, who you can ask?
If you are under the care of a doctor, then I would not caution against it so much.
Regarding using a psychedelic drug (not hallucinogenic) with a baby: that's something for you and your doc to decide. If you can be free of distractions when you use it, then the potential is that it might make you more focused and attentive to the babe, not less. If you're breastfeeding, THC can pass through breastmilk so that's another thing to consider.
As stated above, it might also make you more anxious or paranoid, but that is true with nearly any antidepressant. I wouldn't take it without changing some other things too. You should make sure your environment is positive and relaxing. If your house is a mess and it makes you anxious, then using medical mj would probably be a bad idea unless you can walk around outside or something.
It would also be good to have a doc to whom you can describe any negative effects that you notice.
Some other natural treatments for depression would be to improve your diet, exercise and try to find some way to get involved in social activities (you may already do these things, and still need help. I understand that, and I'm not trying to make any assumptions here.)
I stayed home with my son for the first two years and I had a lot of depression. I worked through it on my own, but in retrospect, I do wish I would have gone to a doctor for the support, if nothing else. Sometimes just having someone to reassure you & talk to you about options can be helpful, if the ppd is mild. My doc recommended daily exercise, so I began running and weight training and I have improved my life a lot. I still suffer with mood swings, but I would not say I have experience full-blown depression since those early years after my son was born.
As others have said, the psychoactive properties of MJ might really amp up the stuff your feeling with PPD. I really suggest finding therapist/dr who specialize in treating PPD and taking a standard antidepresent. There are a lot of other meds besides Zoloft. I bf'ed while taking clexia with no side effects to baby. Is always a benefit and risk balance, but I was encouraged that biggest concern my ped had was lack of weight gain for the baby (besides having a crazed mama for the baby!). The first med you take might not be the right match and you do have to be pro-active about your treatment which is really hard when you feel like you can barely move off the couch. But you have a little one who needs you.
You said that you've already tried other non-pharm treatments (exercise, st. john's wort) maybe now is the time to try more mainstream things. I can tell you that I could have written what you described 2 years ago. I never really felt "sad" but just totally out of it, lacked any kind of maternal bond with my child (and felt intense guilt about that), wanting to be away from all of it or getting really angry about everything. You don't have to feel this way. Your baby deserves a happy mama. You deserve to feel like a normal person and to enjoy your life.
I got on meds and did therapy with the RIGHT therapist and worked my stuff out. The meds were only a crutch to get me stable. I can tell you that for me, the right med was an almost immediate relief from the worst of it. I did continue the therapy for 6 months but I look back to the first year of my kiddo's life and think why did I wait until she was 6 months old to get this under control. The good part is that she didn't know that I wasn't really there.
Best of luck but know that you are not alone. There are probably post-partum support groups in your area. Contact the health department or local L&D dept of your hospital to get in touch with some support. Keep talking and reaching out to people, IT WILL GET BETTER!
No way! I'd stay away from it. Smoking pot makes a person more mellow and more likely to get depressed. When I was younger - I always felt sad and paranoid after smoking it and it gets worse the longer you smoke it.