About one in ten women experience depression during pregnancy or shortly after giving birth. This is among the most common complications related to pregnancy, and is generally treatable if recognized. In early August the FDA approved the first rapid-acting pill, zuranolone (Zurzuvae) to treat severe postpartum depression.

Currently, if a woman experiences a new onset of depression anytime during pregnancy or in the first four weeks postpartum, it is classified as the same condition—“peripartum” or “perinatal” depression—in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) used by psychiatrists to make diagnoses.

However, in many cases and in particular ways, depression during pregnancy may be different from postpartum depression. Several past studies have shown that depression during pregnancy is often (although not always) linked to depression before pregnancy, and can be associated with a number of potential causes: lack of social support, unplanned pregnancy, a history of physical or sexual abuse, or cessation of antidepressant medicines once pregnancy begins.

Depression that begins following childbirth—“postpartum depression”—may be more likely to be associated with the dramatic drop in such hormones as estrogen and progesterone after giving birth.

It is also notable that some of the symptoms of depression during pregnancy and depression that begins after childbirth can differ dramatically. Postpartum depression much more often involves intrusive violent thoughts, and/or obsessive-compulsive and sometimes suicidal thoughts and behaviors.

“Some researchers have argued that postpartum depression might be considered a distinct disorder,” notes Nina M. Molenaar, M.D., Ph.D., of the Icahn School of Medicine at Mount Sinai and the Erasmus Medical Center in the Netherlands. But she acknowledges that more research is needed in order to reconsider the DSM-5 classification.

Dr. Molenaar led a team to study moderate and severe depression before, during, and after pregnancy from a dataset of depressive episodes—both first-time and recurring—surrounding first pregnancies in Denmark from 1999 to 2015, which included 392,287 pregnancies. Anna-Sophie Rommel, Ph.D., of the Icahn School of Medicine at Mount Sinai, a 2020 BBRF Young Investigator, was a member of the team. They reported results in the Journal of Affective Disorders.

The Danish data has the advantage of including all residents in the country, who are all part of a Civil Registration System that links people to their health records, including psychiatric inpatient and outpatient visits. Because healthcare in Denmark is free, anyone who seeks access to care is able to get it, potentially giving more data about depression than in a country where residents have to pay to access mental healthcare.

The team’s analysis revealed several surprising trends. First, both the incidence and recurrence of depression treated in an office setting (i.e. outpatient) increased during the first two trimesters of pregnancy, but not in the third trimester. “This finding is novel, because prior reviews and meta-analyses have concluded that no conclusions can be made regarding the relative incidence of depression among pregnant (and postpartum) women compared with women at non-childbearing times,” Dr. Molenaar explains. The team speculates that this increase in depression prevalence in the first two trimesters could be due to women decreasing or ceasing antidepressant medication, which up to half of pregnant women taking such treatments are reported to do.

For more severe depression with inpatient treatment (i.e. hospitalization) during pregnancy, the data showed incidence and recurrence of psychiatric admission was lower than before pregnancy.

Also noted in the Danish dataset: after women gave birth, the rates of both inpatient and outpatient depression incidence increased considerably. Consistent with other studies, the team observed that “the first-time and recurrent number of depressive episodes treated at psychiatric inpatient facilities were highest during the 12 months after childbirth, with a peak in incidence in the second month after childbirth,” according to Dr. Molenaar. First-time treatment at outpatient facilities, the team’s data indicated, was most common in the first 5 months after childbirth.

These data suggest that the DSM-5 classification of “peripartum depression”—occurring through the first 4 weeks after birth—does not therefore capture a large number of birth-related cases that extend out a full year following childbirth.

“In light of our findings and those of others, we suggest distinguishing the timing of depression onset,” the team wrote. This would yield two rather different diagnoses: depression with pregnancy onset OR depression with postpartum onset (and without limiting postpartum depression to only the first 4 weeks following childbirth).

Changing the definition based on timing of depression onset has the potential to improve treatment of depression during pregnancy and following childbirth, Dr. Molenaar and colleagues propose. “Not immediately,” Dr. Molenaar says. “But after we perform more research studies that can focus specifically on one group and then the other, and test treatment methods within those groups, we might find treatment effects differ between groups with different onset. There might also be a difference in prognosis between these groups.”

“There is still a lot we don’t know about underlying causes of depression during pregnancy and following childbirth,” Dr. Molenaar says. “But finding the best treatment options for each individual is something that we can work towards.”