A viral infection in a pregnant woman not only affects her subsequent ability to provide maternal care but can also trigger depression in her offspring, which can then even extend into the next generation as a result of changes to genetic mechanisms in the brain. This is the central finding of a transgenerational study conducted at MedUni Vienna in collaboration with the Division of Neurophysiology and Neuropharmacology (Daniela Pollak) and the Division of Neonatology and Paediatric Critical Care (Angelika Berger), which has now been published in the leading journal Brain, Behaviour and Immunity.
The researchers were able to demonstrate the following effects in the mouse model:
1.) stimulation of the immune system, comparable with a viral infection in the pregnant mother, results in diminished maternal behaviour towards her offspring after birth.
2.) this results in the tendency for offspring to develop depression and
3.) that daughters in their turn are less maternal towards their own offspring, even if they suffer no infection, so that the next generation is also more likely to develop depression.
"We were therefore able to show that there is a transgenerational effect and that epigenetic changes occur in the brain," explains Daniela Pollak, who, together with her team, is generally concerned with identifying the neurobiological bases of psychiatric illnesses, particularly depression and anxiety disorders.
Although epigenetic changes do not involve any change in the actual DNA sequence of the individual in question, changes due to external influences -- such as the lack of maternal care in this case -- take the form of changes in DNA methylation (modulation of the basic building blocks of the genetic material of a cell) or histone acetylation (modulation of the histone proteins). Says Pollak: "This brings about a change in the regulatory mechanisms, how the genes are read." This leads to a permanent behavioural change or development of a mental illness.
Additional studies are now required to clarify the causality -- for example, whether infection of the mother in itself affects the baby's brain and is responsible for development of depression -- and also what exactly happens in the mother's brain during infection. Further studies will even look at the father's behaviour.
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