Disrupted biological rhythms in teens can produce unexpected brain effects

A new McGill University-led study suggests that disrupting the body's internal clock during adolescence can alter how the brain responds to an in-utero risk factor linked to certain brain disorders.

Previous research has shown that a mother's infection during pregnancy, such as the flu, can increase a child's risk of developing conditions like schizophrenia and autism spectrum disorders later in life. Irregular sleep patterns – often a sign of circadian rhythm disruption – are also associated with these conditions.

To investigate how these factors interact, researchers exposed mice to either a prenatal infection, circadian disruption during adolescence (via constant light exposure), both or neither. They found that each factor caused some changes on its own, but the combination altered memory, anxiety, social behaviour and gene activity in brain regions associated with the disorders.

"While more research is needed, our findings suggest that people exposed to multiple risk factors may need to be especially mindful of their daily rhythms," said lead author Tara Delorme, who conducted the research as a PhD student at the Douglas Research Centre.

Surprisingly, the combined effects didn't always make outcomes worse.

We assumed the effects would be additive. But in some cases, disruption of biological rhythms actually reduced the impact of prenatal infection. That suggests these factors may interact in unexpected ways."

Nicolas Cermakian, senior author, professor in McGill's Department of Psychiatry

The researchers focused on adolescence because it's a sensitive period for brain development.

"Adolescents are vulnerable," said Cermakian. "Their internal clocks tend to run later than the rest of the population, but school still starts early. On top of that, evening exposure to screens and artificial light can further delay their biological rhythms, leading to what we call social jet lag."

This mismatch between the body's internal clock and daily schedules has been linked to a range of health issues, he added.

The research team, including McGill psychiatry professors and Douglas researchers Lalit Srivastava and Patricia Silveira, is now investigating the gene changes the researchers saw in mice to see what they might reveal about how the human brain develops.