Does postpartum depression serve some evolutionary purpose?
—Clint Johnson, Ridgecrest, Calif.
Anthropologist Edward H. Hagen of Washington State University replies:
Postpartum depression (PPD), which afflicts 10 to 15 percent of new mothers, may have evolved as a strategic response to a lack of social support because it helped in passing on genes successfully. Many doctors believe PPD is triggered by the changes in a mother’s hormones after giving birth, yet studies have failed to find much evidence for a link between extreme hormone fluctuations and PPD. The fact that fathers, who do not experience such changes, also suffer from PPD is strong evidence that it is not “just hormones.”
The finding that PPD often plagues people who have marital problems or little outside support led biologists Randy Thornhill and F. Bryant Furlow of the University of New Mexico and me independently to propose that PPD has an evolved function. Many animals improve their chances of passing on their genes if they desert their young when food or parenting help is scarce and invest instead in future offspring that are more likely to survive and reproduce.
This “parental investment theory” should apply especially well to humans. Human children are “expensive” to raise, requiring years of parenting before they can survive on their own. When a mother lacks support from the father or other family members, she may unconsciously conclude she cannot successfully raise her infant. The ensuing emotional pain from PPD operates somewhat like physical pain: stop what you’re doing—it’s harming your reproductive fitness! Studies confirm that mothers with PPD do significantly reduce parenting efforts and often have thoughts of harming their baby.
This “psychic pain hypothesis” cannot explain the whole story, however, because few parents suffering from PPD abandon their newborn. I propose an additional function of PPD that is like a labor strike, in which a mother’s reduced interest in her baby may serve to elicit help from others. Studies do suggest that higher levels of PPD symptoms in mothers motivate more child care by fathers, and increased social support is one of the best predictors for the remission of PPD.
These hypothesized functions for PPD are far from proved. If you or a loved one is suffering from PPD, contact a doctor immediately—treatments, including antidepressants and talk therapy, are available and effective.
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14 Comments
Add CommentAs a biological anthropologist and someone who's been through postpartum depression, it worries me to see too much eagerness to slap an adaptive explanation onto PPD. As scientists, its our responsibility to acknowledge that we cannot explain everything, and not everything has a purpose. Sometimes things are coincidental--sometimes they're the result of maladaptive traits being tagged onto adaptive ones: Perhaps the hormonal shifts themselves are highly adaptive, but their ability to completely throw a new mother's mind out of whack is not. Assuming that everything is an adaptation, or failing to present the possibility that there are good scientific explanations besides adaptive ones for certain phenomena ultimately undermines our credibility as scientists with those who don't agree with the adaptive explanations for which we have good evidence. The scientific community (including myself, Edward Hagan and SciAm) has a responsibility to the public to avoid simply providing stimulating or fascinating potential explanations using evolutionary theory--we also need to provide good, proven explanations for potentially evolutionary phenomena. Let's not get too Panglossian here.
Reply | Report Abuse | Link to thisPPD also happens to women in good relationships with lots of support after having babies they wanted very much.
Reply | Report Abuse | Link to thisThere are plenty of other possible hypotheses:
* mistaken diagnosis of PPD when the real problem is situational depression, so that women in bad situations are counted as PPD when they're really situationally depressed;
* greater chance of diagnosis of PPD when a woman is also unhappy with her situation in general because she may be more more likely to seek support from others or to appear to need help and have it recommended or forced upon her;
* additive effect of situational depression plus PPD when PPD occurs means those who already have situational depression are notably more depressed when struck with PPD, hence more likely to be diagnosed.
This article is a sad example of not only a pharmaceutical misinformation campaign but a blind acceptance of dogma concerning PPD. Regardless of your hypothesized explanations for "evolutionary purposes" of PPD, you have clear falsehoods printed here when you say that antidepressants are effective. See http://online.wsj.com/article/SB120051950205895415.html?mod=hps_us_at_glance_pj Antidepressants Under Scrutiny Over Efficacy, Sweeping Overview Suggests Suppression of Negative Data Distorted View of Drugs By DAVID ARMSTRONG and KEITH J. WINSTEIN January 17, 2008;
Reply | Report Abuse | Link to thishttp://www.netpowwow.com/unite011109/plosarticle.pdf
Drug–placebo differences in antidepressant efficacy increase as a function of baseline
Reply | Report Abuse | Link to thisseverity, but are relatively small even for severely depressed patients. The relationship between
initial severity and antidepressant efficacy is attributable to decreased responsiveness to
placebo among very severely depressed patients, rather than to increased responsiveness to
medication. (From PLOS Article)
Also see the BLACK BOX SUICIDE WARNINGS on antidepressants and the side effects list which includes homicidal ideation, psychosis, hallucination, worsening depression, etc. Please don't be careless when the lives of mothers and babies are at stake because of fraudulent claims and misinformed people pushing their beliefs.
The purpose of science is to observe, predict, and ultimately explain. Evolutionary theorists face difficult challenges because they are observing outcomes rather than actual processes, so the prediction component of their theories becomes the benchmark of a good theory. Dr. Hagen has proposed a potential relationship between PPD and environmental factors that makes very testable predictions. To discount his theory simply because it contradicts what we might currently think to be true is intellectually dishonest. If the data suggest that there is no validity to his proposed theory of PPD, the theory will disappear, just as most poor theories do. Until the data are in, it is ANTI-scientific to chide the theory because of a general discomfort with evolutionary theories. Acknowledging that we cannot explain everything is fine as long as you do not stop trying to explain everything. Throwing one's hands up in despair and saying that "we'll never know the truth" is as sure a path as any to never finding the truth.
Reply | Report Abuse | Link to this"To discount his theory simply because it contradicts what we might currently think to be true is intellectually dishonest."
Reply | Report Abuse | Link to thisYou make it sound like someone's rejecting the hypothesis (it's not even a theory yet) because it makes them unhappy or upsets their personal beliefs.
I'm not seeing that, and I think it's "intellectually dishonest" to suggest that presenting alternative hypotheses and asking Hagen and all scientists to be cautious about how we present hypotheses and early theories to the public is somehow turning one's back on science.
We are supposed to neither cling ruthlessly to the old, nor jump carelessly to the new. No one's clinging. We're asking, is there something actually supporting this hypothesis? If not, don't feed the evo-psych wackjobs any more ammunition for their just-so stories.
Being displeased with the publicity that this idea has received is different than being displeased with the idea itself. Cautious presentation of new theories to the public is certainly admirable, but cautious theorizing is a different story. Cautious theorizing is not a benefit to science. The scientific method will naturally dispense with theories whose predictions do not pan out. All things being equal, from a statistical standpoint, knowledge is likely to progress more quickly when more theorizing and testing occurs. Some of the theories produced in such a high-volume model will be poor, but some will also be accurate. Because the process of the scientific method will self-correct, in the end we will have a greater number of accurate theories, and no greater number of poor theories.
Reply | Report Abuse | Link to thisFurther, calling evolutionary psychologists "wackjobs" belies the assertion that your opposition is based on rationality rather than emotionality and misunderstanding.
This question was in response to an article in Sciam back in Feb (I think) 2008 (http://www.sciam.com/article.cfm?id=misery-in-motherhood). While it is perhaps likely that PDD is simply wide-spread dysfunction (as high as 60%, if I recall), could it serve a function just as nesting does? In the 2008 article, one of the observations made was that PPD seems to affect those in third-world environments at a higher level of incidence. Attributes of such environments likely include a lower sense of security (either personal or resource), although there might be other common aspects that Im missing. Behavior in people (and animals) can be influenced by security concerns, and at a level that is not always conscious. I dont mean to in any way diminish the experience of anyone who was gone through PPD, but could it be that our most powerful experiences are those we are wired to be strongly motivated by (like surviving, falling in love, building a home)?
Reply | Report Abuse | Link to thisI wonder also if psychopathology could be an advantage (see http://www.sciam.com/article.cfm?id=what-psychopath-means). This almost exclusively male affliction includes very low empathy and a high degree of confidence and the ability, at least in the short term, to command the room . Does a psychopathic man have more opportunities to reproduce if he doesnt care about commitment, honesty, etc?
I posed a case a few years ago where I described the basic definition of PPD to a group of physicians but altered one important fact, that the sufferer was male. The response was a relatively bored and quite immediate, "protein deficiency". I would respectfully suggest that in at least some cases of PPD, given the pressures of body image and 'super mum' syndrome, simple dietary modification to include high quality protein would moderate many of the 'typical' PPD symptoms.
Reply | Report Abuse | Link to thisGiven the protein price paid by the mother for construction and maintenance of a growing baby, anything more than a short term deficit in protein intake must result in a clinical deficiency.
I have applied this to my own practice and have had amongst those who have responded (approx 30 - 35%), an excellent resolution of their 'PPD' symptoms. Those who failed to respond to dietary protein also reported a great many co-factors (many of which are mentioned in other comments) required a combination of pharmaceutical and/or psychological support.
There may be many causes of PPD. Not everything has an adaptive purpose, that is a misunderstanding of evolutionary theory! Besides, an example how not always to trust medicine. My wife was given a nasal spray after giving birth, which was supposed to start the breast-feeding process and be generally helpful. She got very depressed and I told her to quit using the spray. Her depression lifted immediately. So be careful, men and women, what they recommend after giving birth.
Reply | Report Abuse | Link to thisA very interesting theory. We're finding out so much about our brains, evolution, and why we do/feel the things that we do.
Reply | Report Abuse | Link to thisA very interesting theory. Amazing to think of all of the things that we are discovering about our minds/development.
Reply | Report Abuse | Link to thisMost studies show that hormonal imbalance plays a role (levels of estrogen, progesterone, and cortisol fall dramatically within 48 hours after delivery - women who develop postpartum depression may be more sensitive to these hormonal changes)
Reply | Report Abuse | Link to thisMost studies show that hormonal imbalance plays a role (levels of estrogen, progesterone, and cortisol fall dramatically within 48 hours after delivery - women who develop postpartum depression may be more sensitive to these hormonal changes)
Reply | Report Abuse | Link to thisRead more: http://neurocyte.net/general/new-research-on-postpartum-depression/