California residents with severe mental illness are being screened for cervical cancer at much lower rates than other women, despite their increased risk for developing the disease, according to a new study.

The study, “Rates of Cervical Cancer Screening Among Women With Severe Mental Illness in the Public Health System,” appeared April 17 in the journal Psychiatric Services.

Thanks to widespread screening for the disease, U.S. cervical cancer incidence and mortality rates have fallen since 1975. But some studies have found lower rates of screening among women with severe mental illness — particularly among those with schizophrenia or other psychotic disorders.

Hoping to learn more, a team led by Christina Mangurian, MD, associate professor of clinical psychiatry at UC San Francisco, analyzed the California Medicaid administrative records of 31,308 women from 2010 and 2011. She directed the study with Dean Schillinger, MD, a UCSF professor of medicine and member of the UCSF Helen Diller Family Comprehensive Cancer Center.

Among the women included in the analysis, 42 percent had some form of schizophrenia, 29 percent had major depression, 18 percent had bipolar disorder and the rest had anxiety or some other psychiatric diagnosis.

The researchers found that overall, only 20.2 percent of women with severe mental illness were screened for cervical cancer during the study’s one-year duration, compared to 42.3 percent, the screening rate for the general population of women in California was 42.3 percent.

Severely mentally ill women aged 28 to 37 were more likely than similar women from the 18-27 age bracket to have been screened, mirroring differences in screening by age among the broader population of California women. Additionally, the 74 percent of women who had sought primary care were three times more likely to have been screened for cervical cancer than women who had not used primary care services. Healthcare use was closely linked to the likelihood of cervical cancer screening.

“The women were receiving services in a public health setting, but were not receiving preventive services as often as women in the general population,” Mangurian said in a news release. “The results of this very large study indicate that we need to better prioritize cervical cancer screening for these high-risk women with severe mental illnesses.”

She added that previous research shows that women with severe mental illness are more likely to be smokers and have more sexual partners, putting them at higher risk for cervical cancer.

When considering potential factors associated with cervical cancer screening in women with severe mental health illness, researchers found that age, race, ethnicity, specific mental health diagnosis and — most importantly — utilization of primary care services were all predictors of screening.

Interestingly, women with bipolar disorder, major depressive disorder or generalized anxiety disorder were more likely than those with schizophrenia to have been screened.

Added Schillinger: “More research is required to better understand why cervical cancer rates are so much higher in this population of women with severe mental illnesses, but I think we already know enough to begin evaluating strategies for removing barriers to care.”