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A recent study of more than 3.8 million women who gave birth in California found that those who were multiracial were more likely to have been diagnosed with bipolar disorder compared with women of a single race.

The number of women in the study sample with bipolar disorder diagnoses was more than 19, 260. While about 3.6% of the women in the sample were multiracial, they accounted for 9.7% of the bipolar disorder diagnoses, the team found. The study, led by researchers at the University of Illinois Urbana-Champaign, was published in Frontiers in Psychiatry.

"Further examination of the multiracial group revealed higher odds of having a bipolar disorder diagnosis among women who reported that they were biracial Black white, and those who were American Indian/Alaska Native/white descent or of Black/American Indian/Alaska Native heritage compared with single-race white women, " said first author Dr. Mercy Eigbike, a psychiatrist at Carle Foundation Hospital in Urbana, Illinois, and a clinical professor in the Carle Illinois College of Medicine.

The sample included women who had singleton live births from 2011–2019 and were part of a linked dataset that included hospital discharge records and birth certificates, which the researchers used to extract information on clinical and demographic characteristics. Women whose discharge records included any of several diagnosis codes related to bipolar disorder or an unspecified episodic mood disorder were considered to be cases of bipolar disorder for the study, while the rest of the women in the sample were in the control group.

Bipolar diagnoses were highest among women who were biracial Black Asian, followed by those who were Black white and those who were Asian white, the team found.

Eigbike said there are many possible explanations for the higher incidence of mental illness among multiracial women, including a lack of access to quality health care, adverse social determinants of health such as socioeconomic status and education, and possible systemic racism.

Women who were of American Indian/Alaska Native descent represented 1.3% of the bipolar diagnoses and Native Hawaiian/Pacific Islanders represented 0.3%. Respectively, these groups composed 0.3% and 0.4% of the sample population in the study.

"It is known that people of biracial American Indian/Alaska Native heritage have increased prevalence of general psychiatric disorders, " Eigbike said. "It may be related to multigenerational trauma and differences in exposure to stress in this population."

Because these groups have been underrepresented in past research, further studies are needed to document the patterns and characteristics of serious mental conditions during the perinatal period, the team wrote.

Sample selection. Credit: Frontiers in Psychiatry (2025). DOI: 10.3389/fpsyt.2025.1550634

"Several studies have come out over the past year—and I have several under review—that show increased burden of perinatal mental health problems among multiracial people, " said co-author Karen M. Tabb, a social work professor at the university and a faculty affiliate at Carle Foundation Hospital in Urbana.

"But prior studies did not contextualize the data. What is very interesting about this paper is that we opened up the multiracial category and started looking within the subgroups, and the findings trended with higher incidence of mental health problems in adults of American Indian/Alaska Native heritage."

The sample for the current study was drawn from California because of its uniquely diverse population, which includes significant numbers of women of multiple racial combinations, the team said.

The odds of receiving bipolar diagnoses among single-race women who were Black, Asian or Hispanic/Latino were disproportionately lower than their proportion of the sample population, the researchers said. For example, while Hispanic/Latino women represented 48% of the sample, they composed just 28% of the people with bipolar diagnoses. And Asian women—who composed nearly 15% of the sample—represented only 3% of the diagnosed cases, the team found.

However, an opposite effect was found among Black women—who were more than 5% of the sample population but represented 11.8% of the bipolar diagnoses.

These disparities in diagnosis rates among women of color—which are low compared with their proportion of the general population and far lower compared with white women—suggests that many patients may be going undiagnosed or that providers may be misinterpreting their symptoms as a result of racial bias, Eigbike said.

Current practice guidelines on the American College of Obstetricians and Gynecologists' website indicate that all women should be screened for anxiety and depression, and that they be screened specifically for bipolar disorder before administering medication to treat symptoms of either condition.

Although several states—including Illinois, Massachusetts, New York and West Virginia—adopted policies on screening for perinatal depression during prenatal, postpartum or well-child visits, these screeners may not capture symptoms of bipolar disorder, Eigbike said.

"The screeners that are used for perinatal depression are not able to pick up bipolar disorder, so it's very important to screen for it as well, " Eigbike said. "Some patients who present with depression may actually be in the depressive phase of bipolar disorder. Very often they will present with frequent depressive episodes before they manifest with a manic or hypomanic episode."

The team proposed that screening for depression be expanded to include bipolar disorder to better meet the mental health needs of perinatal women. Accordingly, further research is needed to develop best practices for identifying perinatal women in need of treatment for bipolar disorder as well as culturally responsive approaches that meet the needs of multiracial women, the team wrote.

More information: Mercy Eigbike et al, What racial disparities exist in the prevalence of perinatal bipolar disorder in California?, Frontiers in Psychiatry (2025). DOI: 10.3389/fpsyt.2025.1550634  Journal information: Frontiers in Psychiatry