The Knocked Up star wed moviemaker Judd Apatow in 1997 and the couple has two daughters, Maude, 14, and 10-year-old Iris.
Mann's career was in the ascendancy when the couple started a family, and she eventually enrolled in therapy after being plunged into years of despair over her sudden change of lifestyle.
The actress tells British magazine Stella, ""It was so hard to go from being totally self-involved, a young actress living in Hollywood, to being a full-time mom living in the suburbs and going to 'Mummy and me' classes and not having anything in common with the other mums. Judd was working all the time and I was just alone at home with a new baby.
""I went to some therapists and, although nobody was talking about it at the time, I'm pretty sure I was suffering from postpartum depression for a few years.""