Rebecca Cox, a psychologist at Washington University in St. Louis, surveyed roughly 230 women through pregnancy and the months after childbirth, tracking a pattern that most expect but few have rigorously proven: when mothers sleep less, their anxiety climbs.
The perinatal period—pregnancy through the child's first year or two—has long been understood as a time of emotional vulnerability. Postpartum depression dominates public conversation, but anxiety disorders actually affect more mothers during this window. Roughly 15% of people experience an anxiety-related disorder during pregnancy or the postpartum period, along with heightened risk for obsessive-compulsive symptoms. Yet the specific relationship between sleep loss and these conditions has remained underexplored until now.
Cox and her team, including senior author and psychiatrist Mary Kimmel, MD, Ph.D., at WashU Medicine, measured sleep habits and anxiety in their participants across four points in time: early and late pregnancy, and early and later postpartum. They asked targeted questions—"Are you worrying about the baby?" or "Do you fear harm coming to the baby?"—alongside measures of OCD traits, such as intrusive thoughts that "harmful events will happen unless I'm very careful" or a perfectionist sense that "things are not right if they're not perfect."
The results, published in the journal Sleep, were clear: shorter sleep duration predicted increases in perinatal anxiety and obsessive beliefs over time. The effect was especially pronounced in mothers with lower levels of coping ability—those who felt less in control of their situations. What's more, the researchers found that sleep loss generally precedes anxiety symptoms, not the other way around. In other words, disrupted sleep is a driver, not merely a consequence.
Sleep disruption during this period is nearly unavoidable. Hormonal shifts, physical changes, and the practical stressors of pregnancy and early motherhood conspire against rest. Problems are particularly pronounced in the third trimester, then spike during the early postpartum period before gradually stabilizing. But Cox's work suggests these sleep losses carry mental health costs that deserve clinical attention.
"Trying to prioritize mom's sleep may have benefits for her mental health," Cox said—a straightforward insight with potentially far-reaching implications for perinatal care. Instead of treating anxiety and obsessive thoughts as isolated phenomena, healthcare providers might focus upstream on sleep as a leverage point for intervention. In a period already marked by physical exhaustion and emotional intensity, even incremental improvements in sleep quality could meaningfully reduce the psychological burden many mothers carry.
The findings arrive at a moment when maternal mental health is receiving overdue scrutiny. If sleep disruption is a robust predictor of anxiety, then supporting better rest becomes not just a comfort measure but a mental health intervention in its own right. For mothers juggling hormonal upheaval, new responsibilities, and intrusive worries, better sleep may be one of the most practical tools available—and one that research now validates as genuinely protective.