How do you deal with post partum depressions and how long does it usually last?

Vent if she must. She should find relief in her partner. If there's anyone who should understand her best at what she's going through, it's her spouse. Ask for a time out whenever rest is needed. Studies show that post-partum depression is triggered by lack of sleep and rest. Tell her to always try to start the day with something good to remember, like her child or her family. Never forget to ask for guidance from the Almighty, if she believes in such. Usually, it starts from a few weeks after giving birth until one year. It's most evident, however, within the first three months. Here's a link from Fox News regarding coping with post-partum depression: http://www.foxnews.com/health/2013/07/07/10-ways-to-cope-with-postpartum-depression.html