Depression appears to be passed down from mothers to daughters, say researchers who have been looking at similarities in brain structures between generations. The research is published in the Journal of Neuroscience.
Around 8% of Americans aged 12 years and over are affected by depression. It is commonly found in both mothers and daughters, previous human studies have reported.
Animal studies in the past have shown that when mothers are stressed during pregnancy, this is more likely to be reflected in the brain structure of daughters than of sons, specifically in the corticolimbic system.
The corticolimbic system is used to assess danger, and it is also where emotions are processed and regulated. It includes the hippocampus, amygdala, anterior cingulate cortex and ventromedial prefrontal cortex.
Mood disorders such as depression, anxiety and stress are reflected in changes to this system. These structural changes are most likely to be passed down from mothers than from fathers; they tend to affect daughters rather than sons.
Researchers from the University of California-San Francisco (UCSF), led by Dr. Fumiko Hoeft, PhD, an associate professor of psychiatry, studied 35 families, none of whom had a diagnosis of depression, in an attempt to link the two study areas.
Mothers' and daughters' corticolimbic systems show similarities
The team measured gray matter volume (GMV) in the corticolimbic systems of the parents and children. To do this, they used non-invasive magnetic resonance imaging (MRI).
The results showed far more similarity between mothers' and daughters' corticolimbic GMV than was seen between mothers and sons, fathers and sons or fathers and daughters.
Dr. Hoeft emphasizes that this does not mean that mothers are responsible for depression in their daughters.
Rather, she says:
"Many factors play a role in depression: genes that are not inherited from the mother, social environment, and life experiences, to name only three. Mother-daughter transmission is just one piece of it.
[The research] opens the door to a whole new avenue of research looking at intergenerational transmission patterns in the human brain."
This is the first time that MRI has been used in this way, for this kind of study. Dr. Hoeft believes that the tool can be used to investigate depression and other inherited neuropsychiatric conditions, such as anxiety, autism, schizophrenia and dyslexia.
MRI technique could shed light on other conditions
To consider further variations not covered by this study, the team plans to use the technique to look at brain structures in cases involving in vitro fertilization (IVF) in conception and/or delivery.
- The age group in which depression is most prevalent among Americans is 40-59 years
- It is more common in females than in males in all age groups
- 12% of females aged 40-59 years experience depression, the highest rate of all groups.
Participants will be birth mothers who were implanted with a donor egg, children born after the biological mother's egg was implanted into a surrogate and mothers who were implanted with their own fertilized egg, known as homologous IVF.
The study could show whether post- and prenatal influence from the mother affect the corticolimbic system, even where there is no maternal genetic input.
Hoeft explains, "In gestational surrogacy, there is genetic and postnatal input from the biological mother, but no prenatal input. With homologous IVF, there are maternal genetic, prenatal and postnatal influences. Comparison of these three groups allows us to control for potential effects of the IVF procedure itself."
She believes this could shed light on how genetics and the environment, before and after birth, affect the structure and function of the brain, as well as cognitive function.
The researchers also hope to expand their work to cover the areas of the brain responsible for language and rewards and the networks involved in psychosis.
Hoeft concludes: "We will cast a wide net, gain a lot of information and maximize this fantastic opportunity."
Medical News Today has recently reported that depression is more common among children in socioeconomically deprived families.