Additional Study Information: This is a pre-marketing (Phase 2A) multi-site study of an investigational drug, ganaxolone, as a potential treatment for non-psychotic post-partum depression. Eligible subjects who agree by signing informed consent will spend four days on the 5-South Research Unit (5-S) of the New York State Psychiatric Institute. For 6 hours they will have an tube in a vein into which randomly assigned intravenous ganaxolone or placebo will be infused. Mood and adverse events will be assessed throughout their 5-S stay and at weeks 1, 2, 3 and 4. Cohort #1 (9 patients), Cohort #2 (12 patients) and Cohort #3 (13 patients) have completed. Their lack of adverse reactions (side effects) determined that optional dose ranging Cohorts #4 & #5 could be skipped and Cohort #6 can begin recruitment of up to 20 subjects. Furthermore, ganaxolone has shown efficacy in oral formulation for other disorders so is an active compound with which there is considerable human experience. Nevertheless, this on-going study is its first use in post-partum women.