A compelling new study from researchers at King's College London has found that if a pregnant mother suffers depression, it can result in notable biological changes in her baby. This is the first study to suggest that depression in pregnancy can result in long-term biological implications for the child.

It isn't particularly new news to suggest that a mother's well-being during pregnancy has fundamental implications for the development of her child. Prior studies have certainly linked depression in a mother to an increased risk of her child developing depression in adulthood, but any potential mechanism behind this has remained a mystery.

The new study from King's College London set out to draw some kind of connection between the physiological impact of depression, as identified in pregnant mothers, and the ultimate behavior and biology of her newborn child. Recruiting over 100 pregnant women, the study followed the women throughout their pregnancies and up to a year following birth.

Around half of the women had been clinically diagnosed with Major Depressive Disorder, and the other half were considered a healthy control. During pregnancy, blood and saliva samples were taken to assess the women for physiological signs of depression. The women suffering from the condition displayed higher levels of inflammatory biomarkers in blood samples, and increased cortisol levels in their saliva. Interestingly, the depression group also gave birth on average eight days earlier than the control group.

After birth, the newborns were given a standard neonatal behavioral assessment designed to measure alertness and responses to external stimuli. These initial results demonstrated the babies born to mothers with depression displayed poorer results than babies in the healthy control.

Follow up tests over the subsequent 12 months, primarily during immunization procedures, found the babies exposed to increased inflammation from the mother during pregnancy had a higher cortisol response to the stress of vaccination. This suggested these infants were more reactive to stress than their counterparts in the control group.

"Interestingly, the behavioral and biological changes in the baby are not due to mothers' postnatal depression but uniquely to the depression in pregnancy, highlighting the importance of the in utero environment," says senior author on the study, Carmine Pariante.

While any correlation between inflammation faced by a baby in utero and subsequent biological changes after birth is undoubtedly a compelling conclusion, it is still difficult at this stage to draw a clear causal line between the two things. It is unclear whether an acute depressive episode during pregnancy resulted in these fundamental biological changes, or whether those mothers in the depression group were simply conferring a larger heritable trait to their child.

The research does suggest that inflammation during pregnancy directly confers certain traits to a child, and this isn't the first study to imply that connection. A study from earlier this year suggested maternal inflammation can affect the development of a baby's brain. This research again struggled to make a clear causal relationship between the two factors but it still asserted there to be a strong link.

Another recent study suggested the development of schizophrenia could be related back to stresses during a pregnancy modulating the expression of certain genes. That research intriguingly focused on genetic activity that was modulated within the placenta.

Sarah Osborne, first author on the new King's College London study, suggests, "Antenatal depression is common, however, it is also easily diagnosed and treated." While an explicit causal connection between depression in pregnancy and negative biological changes in a baby are still unclear, Osborne does recommend pregnant mothers are vigilant in seeking out treatment for acute depressive episodes during pregnancy.

The research has been published in the journal Psychoneuroendocrinology.