Wednesday, 8 February 2012

When depressed mothers give birth to thriving babies

Shelves of evidence show the long-term, adverse consequences for an embryo of having a mother who is stressed or malnourished during pregnancy. For instance, there's medical data showing that underweight newborn babies are more at risk of heart diseases and other illnesses in adulthood.

According to the "thrifty phenotype" hypothesis, this is because the child is born with a body that's primed for malnutrition. When the baby instead encounters plentiful resources, its metabolism suffers as a result, leading to a long-term increased risk of stroke, heart disease and diabetes.

But what if the prenatal environment were a reliable predictor of the world that's to come? A surprising new study shows that adverse prenatal circumstances, in the form of having a depressed mother, are actually beneficial if that same context endures after birth. The finding is consistent with the "predictive-adaptive response model", which says that adversity in-utero can have adaptive advantages if adversity is also encountered after birth.

Curt Sandman and his team measured the depression levels of 221 healthy women during their pregnancy and for twelve months after their children were born. The babies were subsequently categorised into four groups. There were two "concordant" groups, for whom the environment was the same prenatally and post-natally, as in their mother was either depression-free in both phases or she had depression in both phases. And there were two "discrepant" groups, for whom the prenatal and postnatal environments were different, as in their mother had depression in one phase but not the other.

Here's the take-home finding: babies in the concordant groups exhibited superior scores on mental development at 3 and 6 months of age, and superior psychomotor development at 6 months, compared with the discrepant babies. Crucially, this was the case for both concordant groups. In other words, for babies whose mothers were depressed postnatally, it was those whose mothers were also depressed during pregnancy who fared better. This counterintuitive finding appears to contradict the received wisdom that adversity during pregnancy is only ever associated with adverse outcomes.

Zeroing in on the timings, it was specifically the consistency or not between a mother's depression state at 25 weeks' gestation and her depression state postnatally that had associations with the babies' developmental outcomes. This makes sense because past research has found mothers' depression at 25 weeks' gestation (as opposed to at other times) to be most strongly related with their emotional state postnatally. The researchers said it's as if the unborn child is "most sensitive to maternal signals of adversity when those signals are the most predictive of future outcomes."
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  ResearchBlogging.orgSandman, C., Davis, E., and Glynn, L. (2012). Prescient Human Fetuses Thrive. Psychological Science, 23 (1), 93-100 DOI: 10.1177/0956797611422073

Post written by Christian Jarrett for the BPS Research Digest.

7 comments:

  1. Interesting post and study.

    The Barker hypothesis (and the 'thin-fat body' hypothesis) is an interest concept: http://questioning-answers.blogspot.com/2011/08/barker-hypothesis-and-thin-fat-bodies.html and perhaps one of the best examples of epigenetics in action.

    Regarding the current study, I would be interested to see if there was any effect from nutrition (e.g. were mums supplementing pre-natally) or other environmental exposure as to whether these might be confounders.

    Noting also that epigenetics might extend to SES as per this study description: http://www.bionews.org.uk/page_120662.asp was this also controlled for?

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  2. Thanks for sharing such an informative info. One should not be so much depressed during the pregnancy as it's very harmful for both the mother and baby.

    Clark @ Depression

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    1. Lythea9:13 pm

      Well, yes, depression is bad, but that's not really the point here. More that life is what it is, and we're actually so impressively adaptive that if we're given time to prepare it cannot defeat us. Or at least it can't defeat our offspring. That's pretty awesome.

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    2. It's also immensely heartening news for women who are depressed during pregnancy. Saying "one should not be depressed" is extremely unhelpful and only adds guilt about depression to an already severe mental burden. Knowing that at least it won't necessarily harm your baby must surely be a relief. (Though perhaps the prospect of enduring the same depression while looking after a newborn would counteract that relief!)

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  3. Agreed, very impressive that depression doesn't affect our offspring. We truly are one of a kind.

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  4. Useful information and I learn more!

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  5. Very interesting, so its fine if a mother is depressed during pregnancy as long as she remains depressed after giving birth. If she stops being depressed it could cause damage to the baby? How depressing.

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