Maternal Fears: Your Child Smells it On You

Maternal fears are primal, instinctual; ready to be unleashed at the first sign of danger, either real or perceived.

Imagine this scenario: a door opens as a child’s pudgy fingers linger much too close to the door hinge. Her mother is nearby. Mom’s heart beats faster. She gasps and cries, “Watch out!” quickly moving the child’s fingers away from the source of danger.

Maternal heartbeat slows. Crisis averted. For now.

Growing up, it was heights that freaked out my mom. A railing overlooking the bottom floor of the mall, four stories up? If I dared to inch near to peer over the side, my mom would put her hand over her heart and call my name. “Barbara,” she would say, urgency in her voice. “Move away from there.”

She didn’t scream. She didn’t snatch me away. But I heard that fear in her voice.

I moved away from the railing not so much because I was scared, but out of consideration for my mom because I saw her alarm. I wanted to put her out of her misery, ease her anxiety.

But today? I’m a mother now. A mother of many. And should one of my brood get too close to a railing, my heart will pound and the blood will rush to my face. “My God,” I will think to myself at such times, “I’ve turned into my mother.”

Which leads to the question: how do humans learn fear?

Scientists from the University of Michigan Medical School and New York University collaborated on a study to find out whether rats can “learn” fear from their mothers in the first few days after birth, even fears that relate to events that occurred prior to a mother’s pregnancy. The answer? An unqualified yes.

Jacek Debiec, M.D., Ph.D., worked on the study during a fellowship at NYU under the tutelage of Regina Marie Sullivan, Ph.D., senior author of this just published work. Something had puzzled Debiec about his patients. A psychiatrist and neuroscientist from the U of M, Debiec is originally from Poland and has worked with the children of Holocaust survivors. These patients had well-developed “avoidance instincts,” and experienced nightmares, and astonishingly, even flashbacks of traumatic events their parents had suffered. Debiec felt there had to be some sort of underlying neurocognitive process at work that served as the catalyst for such phenomena.

This small seed of an idea: that maternal fears are somehow transferable, germinated into a study of mother rats and their pups. The working theory of the researchers was that mom gives off a smell when she is afraid. Her babies can lean to associate that smell with specific experiences. In this case, the researchers gave not-yet-pregnant rat mommy mild electric shocks while exposing her to the smell of peppermint.

After subsequent pregnancy and delivery, Mommy rat was once more exposed to the scent of peppermint, this time without the shocks, thus evoking the maternal fear response. A second group of rats served as a control group. These mommy rats were exposed to the scent of peppermint, but not conditioned to associate the scent with fear.

At this point the researchers exposed the baby rats of both groups to the smell of peppermint under various conditions both with and without the presence of the mommy rats.

The researchers wanted to pinpoint the area of the brain involved in the process of learning new fears. To this end, Imaging techniques were employed, along with a study of genetic activity in the brain cells and blood cortisol, to identify the lateral amygdala as the relevant brain structure implicated in this process. This same brain structure is called into use in later life to both detect and plan responses to threats. It made sense then, to the researchers, that the lateral amygdala is the brain structure called into action during the process of learning unfamiliar fears.

Mental health experts have long puzzled over the fact that maternal emotional trauma can have a profound effect on children born way after the fact. This research goes a long way toward explaining the phenomenon of maternal fear transmission. A paper detailing the study has been published in, Proceedings of the National Academy of Sciences in the United States of America.

The researchers hope to continue their work, concentrating on why not all children born to mothers who have experienced trauma suffer the identical effects.

According to Debiec, “During the early days of an infant rat’s life, they are immune to learning information about environmental dangers. But if their mother is the source of threat information, we have shown they can learn from her and produce lasting memories.”

Our research demonstrates that infants can learn from maternal expression of fear, very early in life. Before they can even make their own experiences, they basically acquire their mothers’ experiences. Most importantly, these maternally-transmitted memories are long-lived, whereas other types of infant learning, if not repeated, rapidly perish.”

Debiec now hopes to reproduce these results in human infants and will be working with U-M psychiatrist Maria Muzik, M.D. and psychologist Kate Rosenblum, Ph.D., to begin the next phase of this research project. Muzik and Rosenblum manage a Women and Infants Mental Health clinic and research program and work with military families, too. The three are now seeking women and their children to participate in this research. Do you live nearby? Call the U-M Mental Health Research Line at (734) 232-0255 to get more information.

This research was funded by the National Institutes of Health (DC009910, MH091451), and by a NARSAD Young Investigator Award from the Brain and Behavior Research Foundation, and University of Michigan funds. Reference: www.pnas.org/