It seems like a no-brainer idea: screen women after they give birth for postpartum depression and you will find more of the disorder. But a University of Minnesota study, released today, found that it isn't so simple.

The number of new mothers seeking treatment in New Jersey didn't change, the study found, even after the state became the first to mandate screening. The finding has implications for Minnesota. The state already requires that information on postpartum depression be distributed to new mothers. But state leaders are reportedly mulling a mandate as well. Screening recommendations also exist in federal health reforms.

Postpartum depression is a temporary series of symptoms, including sadness, fatigue, anxiety and lack of concentration. Nearly one in five women who give birth suffer from the disorder, but far fewer seek treatment because they don't recognize the symptoms or are too tired or ashamed to act on them.

Mayo Certified Nurse Midwife Mary Murry described the dilemma recently:

After waiting months for your baby's birth, maybe with some anxiety, you marvel at the miracle of the newborn in your arms. You begin to weave the new member of the family into the fabric of your days and nights.

At the same time, you might find yourself sitting on the couch in the middle of the afternoon, still in your pajamas and needing a shampoo. You see dishes in the sink, dirty laundry overflowing the hampers and dust bunnies lurking under the furniture. The tears might start to flow as you wonder when you'll get more than an hour and a half of sleep at a time. Perhaps you're angry or resentful of your partner, who's out in the world with other adults — not up all night with the baby, and not doing laundry or evicting at least some of the dust bunnies. A fear of being discovered to be a bad mother may be lurking in the back of your mind. Is this baby blues or postpartum depression?

One of the clues is the length of time you've been feeling this way. The anxiety, mood swings and irritability of baby blues tend to last a few days or weeks. Postpartum depression is more severe and long-lasting. Symptoms tend to get worse, rather than better.

No doubt confusion also exists because of the high-profile cases, such as the deaths of the Andrea Yates' babies in 2001. Few cases result in psychotic symptoms, yet people may associate the disorder with that level of tragedy.

Which brings us back to why mandatory screening would seem to offer so much promise. The lead author of the U study, Katy Kozhimannil, said a series of policy missteps may have doomed the New Jersey effort. The state didn't enact any way to monitor whether screening takes place, or to enforce that doctors provide screening.

The state required screening before women were discharged from hospitals with their newborns -- too soon to really detect symptoms. And while the state also called for screening at a later time, there was confusion whether it would be done by the womens' doctors or their kids' pediatricians.

The U study had some limitations. It only examined whether low-income women on Medicaid received medication, counseling or other treatment for postpartum depression after giving birth. So it's possible that screening did work for the privately insured or more affluent mothers. Kozhimannil said it is important to focus on the low-income population, though, because they might be at greater risk for the disorder and have more financial barriers to accessing treatment.

Kozhimannil said other states should study screening at smaller levels first before mandating it. Studies like that would identify what approach to screening works best, and why some women with positive screenings for postpartum depression don't then seek treatment.