Why are my wife's moods swinging all over the place? post partum depression?

It might: If you and your wife recently had a baby than depending on the time passed, it could be either baby blues or post-partum depression. Encourage your wife to get evaluated (you can get a referral from her obgyn or child's pediatrician), be supportive, share chores to decrease feelings of being overwhelmed. Eval and treatment are necessary for the well-being of your family, your wife and your baby.

Ppd: Cycling is more common in pod if there is history of mood disorder prior to pregnancy, if complications during pregnancy, or unknown.