Every cell in the human body contains the same DNA sequence, but different genes are turned on or off to make different tissues such as muscle, skin, liver or brain. Amazingly, factors in the environment can also cause epigenetic changes, and this can lead to differences in individual characteristics.
Of interest in our field of research is that very early environmental influences can lead to long lasting epigenetic changes. Initial evidence for this came from the study of rodents and how they care for their young pups. Rats that did not lick their pups a lot when they were young (akin to unsupportive and insensitive caregiving in humans) showed increased anxiety and exaggerated stress responses in adulthood. These were due to epigenetic changes within the brains of the offspring, specifically at the receptor for the main stress hormone, cortisol. Similar epigenetic changes have been found in the brains of rats whose mothers were stressed during pregnancy.
From human studies we know that extreme stress may alter the epigenetic regulation of DNA in a child’s brain, also at the receptor for the stress hormone cortisol. Further, exposure to mums stress during pregnancy, caused by inter-partner violence and depression, may also alter the epigenetic regulation of this receptor.
So existing research suggests that epigenetic changes may be one way in which mum’s depression during pregnancy influences the baby’s development.
A recent study from our group has extended these findings. We found that specifically boys, but not girls, who were exposed to mum’s depression during pregnancy, had epigenetic changes at the cortisol receptor. This fits in well with an existing body of research, which suggests that male infants may be more susceptible to the adverse outcomes associated with antenatal depression exposure than female infants.
We also looked at the epigenetic profile of another gene that is related to brain development, and also found that this was changed in those infants of mothers who were depressed during pregnancy. This is a very novel and exciting finding that we will pursue further in future studies.
Interestingly, there was no effect if the mum had depression during the postnatal period on the baby’s epigenetics, which suggests that these changes occur before birth. We don’t yet know exactly how these epigenetic changes may affect the development of the child – there is a lot still to learn, but we at least have some pointers towards the functioning of two key genes.
You can read our full paper about the study discussed in this blog here.