A new theory has emerged about the genetic basis of mental disorders, and it has to do with our parental genes fighting for dominance.

The theory outlines that genes from the father’s sperm are in an evolutionary tug-of-war with genes from the mother’s egg. Whichever becomes dominant tips brain development that direction. An excerpt from the NY Times -

A strong bias toward the father pushes a developing brain along the autistic spectrum, toward a fascination with objects, patterns, mechanical systems, at the expense of social development. A bias toward the mother moves the growing brain along what the researchers call the psychotic spectrum, toward hypersensitivity to mood, their own and others’. This, according to the theory, increases a child’s risk of developing schizophrenia later on, as well as mood problems like bipolar disorder and depression.

A support of the theory are the sister syndromes Angelman and Prader-Will. The Angelman syndrome is characterized by jerky movements, frequent laughing or smiling and an unusually happy disposition. The syndrome is caused by a deletion of genes on the maternally inherited chromosome 15. Contrast that to Prader-Willi syndrome, where individuals are placid, compliant and low-maintenance. The syndrome is caused by a deletion in the same region of a paternally inherited chromosome 15.

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Malnourishment in a pregnant woman has a lasting effect on her child’s DNA. This was the implications of a new study on children born during the famine of World War II.

Scientists studied the DNA of children who were born to women starved during the 1944 Hunger Winter in the Netherlands. They analyzed a gene called insulin-like growth factor 2 or IGF2, an important growth hormone. Methyl groups that attach to IGF2 very early in fetal development determine how much of the growth hormone is made later, and protect the DNA from damage.

The scientists found that those children (now in their 60s)  who were exposed to famine in the first trimester of pregnancy had lesser methyl groups in the IGF2 gene than their siblings of the same sex.

Loss of methylation in IGF2 has previously been linked to colorectal cancer in humans. In this latest study, it’s too early to tell what the epigenetic effects are of a mother’s starvation on the adult life of her child. But the take home from this is that extreme maternal diet (either starvation or eating disorder) does affect the fetal DNA, and those effects leave their mark decades later.