Mothers may pass on vulnerability to depression in much the same way they give their daughters green eyes or curly hair - girls might inherit a brain structure that's predisposed to mood disorders, a small U.S. study suggests.
Researchers focused on what's known as the brain's corticolimbic system, the interconnected brain areas responsible for regulating emotion that also influence depression, stress responses and memory.
They studied the brains of 35 families, including parents and their biological children, and found the particular contours of the corticolimbic system are more likely to be passed down from mothers to daughters than from mothers to sons or from fathers to children of either gender.
"While our study was not directly done in depressed families, our findings may mean that if mothers have brain structural anomalies in the corticolimbic circuitry, their female but not male offspring are more likely to have similar abnormal structural patterns in the same brain regions, which would be consistent with how depression is linked within families," said lead study author Dr. Fumiko Hoeft of the University of California, San Francisco.
Previous behavioral health studies have pointed to a strong link between psychiatric problems in mothers and similar mood disorders in their daughters, Hoeft and colleagues note in The Journal of Neuroscience. Animal research has also linked mothers' stress during pregnancy to changes in emotion-related regions of their daughter's brains.
For the current study, researchers examined magnetic resonance imaging (MRI) of both parents and children to see if they could learn more about how these associations might work.
They found correlations between mothers and daughters in regional gray matter volume in the corticolimbic circuit including several parts of the brain that influence emotions - the amygdala, hippocampus, anterior cingulate cortex and ventromedial prefrontal cortex.
These mother-daughter similarities were significantly stronger than the associations seen between other parent-child pairs.
The findings don't prove that mothers pass along a depression-prone brain structure to their daughters, and the study doesn't mean it's impossible for children to inherit a predisposition to mood disorders from their fathers, the authors caution.
Because of the relatively small sample, the current findings are preliminary and more research is needed with more people to better understand how and why emotional health might be inherited, the researchers also note.
Even so, the findings offer another biological explanation for the strong connection between depression in mothers and daughters, said Genevieve Piche, a psychology researcher at the University of Quebec in Outaouais who wasn't involved in the study.
"Until now, our hypotheses were that maternal depression has a greater influence on girls since it provides them with a model of depressive, cognitive and interpersonal functioning and also may elicit more caretaking behavior in girls, which subsequently could lead them to develop depressive symptoms," Piche said by email.
It's also possible that women who are depressed might minimize the risk of passing this condition to their daughters if they get treatment to manage symptoms, Piche added.
Family characteristics, social context, parenting style and other environmental factors can also play a role in depression, Piche said.
"Being exposed to a depressed mother who has difficulty dealing with her emotions as well as a high level of family conflict and hostility may influence the child to develop more negative emotions," Piche said. "It's not just an individual factor that heightens the risk of depression, but an accumulation of many risk factors."
SOURCE: http://bit.ly/1QoXIBg The Journal of Neuroscience, online January 27, 2016.