We often attribute our key characteristics to one of our parents: “I get my perfectionism from my dad and my impatience from my mom.” In most such cases, though, we do not really know what combination of nature and nurture led to the family resemblance. Now a study has found that the structure of emotion-regulating regions in the brain may be passed down from mother to daughter, which could have implications for mood-disorder risk.

A growing body of research suggests that heredity plays a role in mood disorders—including depression, which afflicts an estimated 15.7 million adults in the U.S. alone. In the new study, published in January in the Journal of Neuroscience, researchers took MRI brain scans of each member of 35 families, all of whom had a clean bill of mental health. They measured the volume of areas in the brain's corticolimbic system, responsible for the regulation of emotion. The results revealed that the relation between gray matter volume in the amygdala, anterior cingulate cortex, ventromedial prefrontal cortex and hippocampus was much more similar in mother-daughter pairings than in mothers and sons or in fathers and children of either sex.

“We joke about inheriting stubbornness or organization—but we've never actually seen that in human brain networks before,” says lead author Fumiko Hoeft, an associate professor of psychiatry at the University of California, San Francisco. The finding suggests a significant female-specific maternal transmission pattern in emotional responses. This could include mood disorders such as depression, although confirming that would mean extending the research to encompass families with a history of such disorders, notes Geneviève Piché, a psychology professor at the University of Quebec at Outaouais who was not involved in the study.

Past evidence from animal research and clinical studies on depression also suggests an element of maternal heritability. Hoeft's study adds new evidence, but she cautions that one cannot yet say whether the mother-daughter similarities are the result of genetic, prenatal or postnatal effects, or some combination of the three. All of these factors may be essential to whether someone develops depression—but locating risk in the female family line may help doctors identify and treat patients early.