Researchers used sophisticated brain imaging scans to show that levels of a brain chemical called glutamate are higher in the brain's prefrontal cortex among women with postpartum depression compared to those without it. Glutamate is a brain chemical that is involved with memory and learning.
Other studies have shown that glutamate levels are decreased in people with major depression.
The findings, which appear online in Neuropsychopharmacology, suggest that there may be important differences between postpartum depression and major depression.
Postpartum depression occurs in up to 20% of new moms. More severe and incapacitating than baby blues, postpartum depression is marked by feelings of hopelessness, severe sadness or emptiness, withdrawal from family and friends, and even thoughts of suicide. These emotions can begin two or three weeks after birth and can last up to a year or longer if it goes unrecognized and untreated.
"Our results suggest that the biology may be different than major depression," says researcher Jean-Michel Le Melledo, MD. He is a psychiatrist at University Hospital in Edmonton, Alberta, Canada. "In most depression studies, glutamate was shown to be decreased in the brain, but it was increased in postpartum depression in this study."
Although the study was small, and the findings do need to be confirmed, it could change how postpartum depression is treated. New compounds in the works target glutamate and seem to kick in much faster than antidepressants aimed at other neurochemicals. These drugs have not yet been tried in women with postpartum depression, but they may have a role.
Still, the reason for the differences in glutamate may be the timing in which the scans were taken. Brain scans in people with major depression are usually done months or years after the onset, while these scans were taken early in the course of postpartum depression.
Postpartum Depression Is Real
"The findings help legitimize postpartum depression for any non-believers," says Catherine Birndorf, MD. She's a reproductive psychiatrist at New York-Presbyterian/Weill Cornell Medical Center in New York City.
Greater awareness about postpartum depression and education about its symptoms will help more women seek treatment. "It is super-treatable and this is such an incredibly important time of life," she says. Still, many women don't come forward because of shame, guilt, and embarrassment associated with postpartum depression.
Dan Iosifescu, MD, urges caution in drawing any conclusions based on this study. He is the director of Mood Disorders at Mount Sinai Medical Center in New York City. But "this study [confirms] ... that there is clear biologic abnormality in the brains of women with postpartum depression," he says. "It is not just them feeling tired and unhappy after having a child."
That said, the study compared women with postpartum depression to healthy volunteers -- not people with depression. For this reason, it is hard to say if the two conditions really do differ. Plus, some studies have shown that glutamate levels are also elevated in people with depression. The literature is mixed, he says.