Sage Therapeutics Inc and Biogen's experimental drug to treat postpartum depression met the main goal of a late-stage study, the companies said on Wednesday.

The drug, zuranolone, showed improvement in depressive symptoms among women with postpartum depression at day 15.

It also met its secondary goals, leading to improvement in symptoms as early as the third day of treatment compared with placebo.

Postpartum depression occurs after having a baby, with symptoms similar to depression but which may also include excessive worrying, crying and feelings of anger.

About 1 in 8 women experience symptoms of postpartum depression, according to the U.S. Centers of Disease Control and Prevention (CDC).

The drug is also being developed for the treatment of major depressive disorder.