Tuesday, September 11, 2012

For The Sake Of The Child. Maternal Depression and Child Height.

I came across these headlines yesterday:

Mom’s Depression May Lead to Shorter Kids

Depressed moms might have shorter kids, new study suggests 

Postpartum Depression May Lead to Shorter Kids: Study

Mother's Depression Linked to Child's Shorter Height

Only that last headline is correct, in the sense that the study all these cover cannot prove causality of any kind.

I read through all those popularizations and then got hold of the article itself (thanks to the funding of you, my sweet readers!).  The study is not bad, as such studies go, but the way it is popularized and discussed is such a beautiful example of how and why certain studies are picked for wider dissemination and others are not.  It is also a beautiful example of the kinds of conclusions that we are offered, together with the gist of the study.

On those conclusions:  

"The hopelessness of depression often leads people not to seek the care that they need," said Robbins. "If [mothers] can make the connection that this is not just affecting them but also affecting their family, it may become motivation to get the proper treatment."

The person quoted there is a psychiatrist and not involved with this study.  I would have thought a psychiatrist would realize that the last thing a severely depressed woman will be motivated (to seek care, not suicide)  by is dumping more guilt feelings on her.  After all, here are some of the symptoms of post-natal depression:

According to the CDC, postpartum depression among women is characterized by the following:
    •    Trouble sleeping when your baby sleeps (more than the lack of sleep typical among new moms)
    •    Feeling numb or disconnected from your baby
    •    Having scary or negative thoughts about the baby; for example, thinking someone will take your baby away or hurt your baby
    •    Worrying that you will hurt the baby
    •    Feeling guilty about not being a good mom, or ashamed that you cannot care for your baby

Now add to those guilt feelings the idea that your child will be stunted because of you.  One has to tread very lightly indeed, to get the message home in a loving and non-blaming way, and I don't sense that from the various conclusions I've read, such as this:

The new research doesn’t explain how kids with depressed moms end up shorter. That’s something the researchers are looking into right now, said the study’s lead author Pamela J. Surkan, an assistant professor at the Johns Hopkins Bloomberg School of Public Health.
Surkan suspects, however, that depression might get in the way of nurturing.
“We think that mothers who are depressed or blue might have a hard time following through with caregiving tasks,” Surkan said.
“We know that children of depressed mothers often suffer from poor attachment and the depression seems to have effects on other developmental outcomes. It makes sense that mothers who have depressive symptoms might have reduced ability to take care of infants, that they might not always pick up cues from their kids.”
 It sounds very authoritative.  Until you learn (as I did) that this particular study has NO DATA on nurturing practices.  The conclusion about child-rearing practices is based on earlier studies, it seems.  Still, this is the first paragraph in one popularization of THIS study, after the headline
"Postpartum Depression May Lead to Shorter Kids: Study":

It's not certain why, but feeding practices might play a part, expert says

Rewind back to that symptom of post-natal depression:    Feeling guilty about not being a good mom, or ashamed that you cannot care for your baby.   I get that this topic is an important one.  But to put something which isn't even based on the study at the beginning of the popularization is kinda bad.  On the other hand,  these ruminations ARE based on the comments of one of the researchers....

What about the study itself?  As I mentioned above, it's not a bad study as such.  BUT it has no data on the heights of the child's parents, none at all.  This means that the results do not take into account the genetic component in children's heights.

And while the study stresses that it has not proved causality from the mother's depression to the child's lower stature it proceeds as if that has been done, by proposing various theories about how the former might cause the latter.  Yet the study also mentions past research into this topic:

Results from other developed countries on the association between maternal depressive symptoms and child growth have been mixed.27–32 Two studies from the United Kingdom examined failure-to- thrive in children age #1; one found no association,30 and the other reported an association only at 4 months that disappeared by 1 year of age.29

 In studies including children followed only until age 2, pooled data from 5 countries showed no differences by depressive symptoms for child weight, length, weight for length, or body mass index.32 However, a case-control study reported that children #2 years old with growth faltering were more likely to have depressed mothers.31

The only US study with follow-up until at least age 3 was from an affluent mostly white sample.27 Unlike other studies, Ertel et al found maternal depressive symptoms at 6 months postpartum associated with increased child height- for-age z scores at age 3.27 Using longitudinal growth models from birth to age 3 to examine weight-for-height z scores over time, they reported no difference between children with and without depressed mothers.28

Only one of the popularizations I've read mentions that other studies have had different findings.

The study controls for various socio-economic variables.  But as mentioned, it has no data on the parents' heights or on the parent's nurturing practices.  Neither has it any data on the father's mental or emotional state.  As is common in these studies, fathers and their behavior is not generally studied (in this study they are present only in the sense of the variable reflecting single-parenthood of the mother or not).

 That is because the job of nurturing is assigned to the mother.  But that omission may prove harmful if family dynamics are affecting the mother's depression.  For instance.

I write about this study not because of the study itself but because of the extent and type of popularization it acquired.  Those earlier studies with all sorts of findings about the relationship between maternal depression and child height did not get this kind of exposure.  Certain studies are pulled out of the file cabinets and highlighted, and those studies usually are interpreted as the whole knowledge of a particular field.  That the overall findings are much fuzzier is ignored.

I also write about this study because of the practical advice the popularizations include.  Those amount to the exhortation that severely depressed women should seek care because they might be hurting their children.  When one important symptom of post-natal depression consists of giant feelings of maternal guilt, this advice seems ignorant at best.

What is the take-home message from all this?  That post-natal depression can be a severe medical condition?  Didn't we know that already?  That it should be treated as a severe medical condition because it might affect the children and not just the mother?