Child behaviour issues linked to prenatal stress

Ottawa study looks at specific upsetting events in lives of 10,000 pregnant women

Pregnant women who experience significant stress have an increased risk of having a child with behavioural problems, says a University of Ottawa study that dissected data on more than 10,000 mother-child pairs.

What’s more, expectant mothers exposed to high levels of stress had children who were more than twice as likely to have chronic symptoms of hyperactivity, a symptom of ADHD, as well as conduct disorders, according to the study published Wednesday in the journal Biological Psychiatry.

“The roots of mental illness can be traced back to the very beginnings of life. We can’t avoid all stress during pregnancy, or at any time. But we can help women avoid stress and manage stress,” said senior author Dr. Ian Colman, an associate professor at the University of Ottawa’s school of epidemiology and public health.

A mother’s stress can alter the fetus’s brain development. Researchers believed these changes may be long-lasting or permanent, Colman said.

“Research shows that when stressful things happen, people are likely to have mental health problems decades later.”

The researchers used data from the Britain-based Avon Longitudinal Study of Parents and Children, considered the “gold standard” of its kind. In the study, which began in 1990, mothers were asked about 42 stressful life events when they were pregnant, including problems at work, the illness or death of a relative, or an argument with a partner, family or friend.

Years later, symptoms of conduct disorder in these women’s children were measured at six, nine and 13 years of age. Conduct disorders are characterized by aggressive or anti-social behaviour and are associated with poor performance in school, substance abuse, difficulties in relationships and criminal activity. The University of Ottawa study adjusted for other possible influencing factors such parental education, class, low birth weight or premature birth and the mother’s smoking, drinking or mental health during pregnancy.

Most studies concerned with a pregnant woman’s mental health have looked at maternal depression and anxiety, Colman said. However, a mother who is depressed or anxious during pregnancy may also be depressed or anxious during the child’s formative years, so that might also affect the child’s behaviour. This study looked at specific events in the lives of the pregnant women.

Colman and his fellow researchers would like to take a more detailed look at the nature of specific stressful events and the corresponding impact on the children to tease out what kinds of prenatal stress are particularly dangerous.

A 2015 article in the journal Advanced Neurobiology suggested prenatal anxiety or depression may contribute to between 10 and 15 per cent of the attributable load for emotional or behavioural outcomes in children. But the biological mechanisms are still unclear. The mother’s cortisol, the hormone released in response to stress, passes to the fetus through the placental barrier and cortisol may prompt a response in the developing fetal brain. Fetal cortisol is also associated with testosterone, which is linked to aggressive behaviour.

About 10 per cent of school-age children are affected by ADHD or conduct disorder. But Colman doesn’t think it’s on the increase. In other research published in the Canadian Medical Association Journal in 2014, he and colleagues concluded there is little evidence that there are more children with behavioural disorders. He believes it’s likely that as the stigma breaks down, parents are more likely to seek treatment for their children.

There has been a lot of interest on maternal stress and how it affects children. In Quebec, researchers are following about 150 families that include a woman who was pregnant or became pregnant during the 1998 ice storm. Researchers found DNA within the T cells of 36 children showed distinctive patterns in DNA methylation, which plays a role in the way genes express themselves.

Colman urges pregnant women to use whatever strategy they find helps to de-stress — meditation, a walk, socializing with friends.

“Having a supportive partner and family members helps,” he said. “It’s in everyone’s best interests to help pregnant women reduce stress.”

Research like this should feed into policy decisions, said Mark Henick, national director of strategic initiatives at the Canadian Mental Health Association.

“This study is certainly reflective about what we know about stress. It validates what we have been saying in the mental health community — stress can be toxic.”

Workplaces also have a role to play in ensuring workers have appropriate workloads, sick leave programs, employee assistance and an understanding of the importance of resilience, he said.

“Resilience isn’t about avoiding stress. It’s about springing back and helping people do that.”

The effects of maternal stress can be felt downstream and they can be costly for a mental health system already under strain, Henick said.

“We can beat illnesses upstream. This impacts more than the mother.”