Pregnant people with multiple sclerosis have a higher chance of experiencing mental illness both during their pregnancy and in the first years after they give birth than those without MS, according to a new study.

Previous studies have shown that women with MS are more likely to have depression, anxiety disorders, and bipolar disorder compared to women without MS. The researchers said mental health struggles can affect both parents and kids, making it important to understand how mental health challenges around pregnancy affect people with MS.

The study by researchers in Canada involved 894,852 pregnant people. Of the group, 1,745 people had MS. They were matched to 869,227 pregnant people who did not have MS. Researchers looked at health records for people who gave birth during a 15-year span. They looked at records from two years before conception to three years after the participants gave birth. Researchers then looked at how many participants had newly diagnosed or existing mental illness during pregnancy, and in the first, second, and third years after giving birth. Mental illnesses included anxiety, depression, bipolar disorder, psychosis, suicide attempts, and substance abuse.

They found that mental illness affected 42 percent of people with MS during pregnancy and increased to 50 percent in the first year after giving birth, compared to 30 percent of people without MS during pregnancy and 38 percent in the first year after birth. A total of 8 percent of people with MS had new mental illness diagnoses during pregnancy and 14 percent had new diagnoses in the first year after birth, compared to 7 percent and 11 percent of those without MS, respectively.

After adjusting for factors such as age at conception and income in the area of residence, researchers found pregnant people with MS had a 26 percent increased risk of mental illness during pregnancy and a 33 percent increased risk after giving birth when compared to pregnant people without MS. In addition, researchers found that people with MS had an increased risk of all specific mental illnesses except suicide attempts. They also found that substance use increased in people with MS from 0.54 percent during pregnancy to 6 percent postpartum.

The researchers said their findings emphasize the need for preventive and early treatment of mental illness and that future studies should look at how MS affects mental health in mothers during and after pregnancy and if it’s worse in different stages of MS. Doctors should know about these risks, make sure to check mental health, and provide treatment if needed.

A limitation of the study was that researchers were unable to look at how severe participants’ MS was, what treatments people were using, or their health habits.

The study published in the journal Neurology.