August 17, 2011 — Children who grow up with a depressed mother, who probably is not as attentive as a nondepressed mother, may develop an enlarged amygdala, the part of the brain linked to emotional responses, a new study suggests.
In the study, researchers observed significantly larger amygdala volume in 10-year-old children whose mothers struggled with depression throughout their young lives compared with their peers who had not been exposed to maternal depression.
Sonia Lupien, PhD, from the Mental Health Institute of University of Montreal, Quebec, Canada, and colleagues report their study online August 15 in Proceedings of the National Academy of Sciences.
Dr. Sonia Lupien
Enlarged amygdala volumes have also been seen in adoptees initially raised in orphanages, the study team notes.
Taken together, the findings suggest that the developing amygdala may be very sensitive to the quality and quantity of maternal care.
"Maternal depressive symptomatology has been associated with reductions in overall sensitivity to the infant and with an increased rate of withdrawn, disengaged behaviors," Dr. Lupien and her colleagues write.
The message, Dr. Lupien told Medscape Medical News, is that it is "important to treat the depressed patient, but also take into account the family unit."
"Many clinicians only concentrate on the patient that they treat, but other members of the family may also suffer from the depression of an adult (spouses and/or children)," Dr. Lupien added.
"No individual is alone in depression and it might be important to take care of the children as well as the mother and/or father in order to prevent the effects of depression from spilling over other family members."
Long-Term Consequences Unknown
Dr. Lupien and colleagues measured hippocampal and amygdala volume as well as stress hormone (glucocorticoid) levels in 17 children exposed to maternal depression since birth and 21 who were not. All of the children were 10 years old at assessment.
They found larger left and right amygdala volumes (P < .01) in the children exposed to maternal depression since birth compared with children without this exposure. They also observed a significant positive correlation between mothers' mean depression score over the first 7 years of the child's life and her own child's mean amygdala volume (P < .0001).
Hippocampal volumes did not differ between children exposed or unexposed to maternal depression, which isn't all that surprising, Dr. Lupien said.
Many studies, she explained, have shown hippocampal atrophy in adults, but not children, who report exposure to childhood adversity.
"This has led to the 'incubation hypothesis' whereby the effects of stress during childhood may only be apparent during adulthood (they may take time to emerge). This would be why we see hippocampal atrophy in adults exposed to early adversity but not in children exposed to adversity," Dr. Lupien said.
The investigators also observed increased salivary glucocorticoid levels (P < .05) in the children of depressed mothers when they were presented with unfamiliar situations, suggesting increased reactivity to stress in those children.
"The long term consequences of this increased reactivity to stress are unknown at this point," Dr. Lupien said.
Sensitive to Neglect
Medscape Medical News asked Nim Tottenham, PhD, assistant professor of psychology, Department of Psychology, University of California, Los Angeles, for her thoughts on this study.
Dr. Tottenham was involved in the study, reported by Medscape Medical News, that found enlarged amygdala volumes and difficulties in emotion regulation in a group of children reared in orphanages (Dev Sci. 2010;13:46-61).
The current study, Dr. Tottenham said, "is very similar to what we had published in children adopted from orphanages (which is important), but I think what is most novel is that these children had experienced a more 'species-typical' rearing environment and yet showed the same phenotype."
"Taken together," Dr. Tottenham said, "the studies are showing that the developing human amygdala is highly sensitive to maternal neglect, whereas the hippocampus, unlike in adults, fails to show an impact during childhood."
"A strength of the paper," she said, "was that all the children were exactly 10 years old and the mother's depression was well-characterized across those 10 years."
"I sincerely think," Dr. Lupien commented, "that developing interventions to help parents and children deal with the stress associated with depression in one family member could provide very positive results for all the family members, and society at large."
The study was supported by grants from the John D. and Catherine T. MacArthur Foundation, the Canadian Institutes for Health Research, and Fonds de recherche en santé du Québec. The authors and Dr. Tottenham have disclosed no relevant financial relationships.
Proc Natl Acad Sci. Published online August 15, 2011.