Philosophy:Evolutionary approaches to postpartum depression

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Evolutionary approaches to postpartum depression examine the syndrome from the framework of evolutionary theory.

Postpartum (or postnatal) depression refers to major and minor episodes of depression within the first 12 months after delivery. Depression during pregnancy is referred to as prenatal (or antenatal) depression. Symptoms of postpartum depression include sad or depressed mood, feelings of worry, anxiety, guilt, or worthlessness, hypersomnia or insomnia, difficulty concentrating, anhedonia, somatic pain, changes in appetite, weight loss or weight gain, moodiness, irritability, restlessness, and fatigue.[1]

Women may also have doubts about their ability to care for a new infant, difficulty bonding with the infant, or thoughts of harming themselves or their infants. In the DSM-V, diagnosis is made under major depressive disorder, with the added specifier “With peripartum onset” if the episode occurs during pregnancy or the first four weeks postpartum.[1] Postpartum depression is not to be conflated with postpartum psychosis, which is qualitatively different.[2][3]

A meta-analysis found that up to 12.7% of pregnant women experience an episode of major depression, while as many as 18.4% experience depression at some point in their pregnancy.[4] However, they did not find a significant difference between these and rates of depression in women at nonchildbearing times. Similarly, one meta-analysis found rates of depression of up to 12.9% within the first year postpartum, and other studies have found similar rates.[5][6]

There is also growing evidence that PPD is under-reported and under-diagnosed, raising concerns that a number of women suffer untreated. Cross-cultural research is often difficult to replicate and synthesize. For instance, one meta-analysis found rates of PPD from 0% to 60% across 40 countries.[7] It is likely that a number of cultural factors likely lead to under- and over-diagnosis in some countries.

Postpartum depression in men

There is growing evidence that new fathers are also at risk of experiencing pre- and postpartum depression, although this remains understudied. Goodman[8] found that during the first postpartum year, the incidence of paternal depression ranged from 1% to 25% in community samples, and from 24% to 50% among men whose partners were experiencing postpartum depression. Others have replicated the association between partner depression and paternal postpartum depression.[9]

Another review found rates of postpartum depression in about 10% of sampled men, with higher rates at 3 to 6 months postpartum.[10] Another review found that along with depression in their partners, low relationship satisfaction was also correlated with paternal postpartum depression.[9] It may also be that adoptive fathers can be at risk of developing postadoption depression, although this requires further study.[11]

Risk factors for postpartum depression

Many studies have examined risk factors in peripartum depression. Although results are sometimes mixed, the factors listed in the table below have been associated with peripartum depression.[12][13][14] A comprehensive meta-analysis found that the most strongly associated risk factors for postpartum depression to be stressful life events, previous history of depression, anxiety during pregnancy, low levels of social support, and low socioeconomic status.[15][16][17]

One study found that the stress hormone placental corticotropin-releasing hormone (pCRH) mediated the relationship between prenatal family support and fewer depression symptoms postpartum.[18] Studies have also shown that infant health issues represent a suite of risk factors for maternal depression, including preterm birth, low birthweight, birth complications, and infant illness.[19] Another review have found additional risk factors including marital status, relationship quality, infant temperament, and self-esteem.[20]

Some researchers have examined diet as a primary risk factor for depression. According to one review, the typical western diet often leads to inadequacies in n-3, folate, B vitamins, iron, and calcium.[21] Depletion of these nutrients during pregnancy may increase a woman's risk for postpartum depression. Cultural factors may also pose risks for postpartum depression. For instance, in cultures with gender preferences for children, unmet preferences are a risk factor.[22]

Risk factors for postpartum depression
low SES
low social support
birth complications
low infant birth weight
preterm birth
unplanned pregnancy
previous depressive episodes
bottle feeding
anxiety
stressful life events
domestic violence
nutrient deficiency
negative attitude toward pregnancy
poor relationship satisfaction
difficult infant temperament
low self-esteem
preference of infant's gender

Evolutionary approaches to postpartum depression

For evolutionary scientists, postpartum depression is of interest due to its relatively high rates and seemingly universal expression, which may provide evidence of functionality. However, postpartum depression is also detrimental to mothers, their infants, and decreases future reproductive success.

Mismatch hypothesis

Another [In addition to?] evolutionary approach to postpartum depression is framed by the changes in human lifestyles in recent history. Hahn-Holbrook and Haselton[23] review a number of lifestyle shifts that have affected humans since the development of agriculture. First, most people today consume grain-fed domesticated animal products rather than wild-caught animals. Unlike wild animals, domesticated animals have much lower levels of omega-3 fatty acids, which are essential to brain development and to fetal health. In support of the theory that postpartum depression may be related to modern diets, the authors find that rates of postpartum depression are lower in countries that consume higher amounts of seafood, which contain high levels of omega-3 fatty acids.[24]

This hypothesis is weakened by the known poor reliability of measures of PPD in Asian samples, which often return low rates of postpartum depression in countries including Japan. Emerging evidence suggests that postpartum depression may be just as common in these samples, but is experienced differently and is not detected by measures including the Edinburgh Postnatal Depression Scale. Furthermore, a direct randomized control trial found no effect of supplementary omega-3 fatty acids in women with postpartum depression.[23]

The authors also review the relationship between breastfeeding and postpartum depression. They do not specifically explore the child loss hypothesis, discussed above [Discussed where?], but instead examine evidence that breastfeeding is related to stress regulation and reduces negative affect, offering a buffer against the risk of postpartum depression. However, since most studies are cross-sectional the direction of this effect is yet to be determined as it may be that depressed women are less likely to breastfeed than non-depressed women.

Finally, the authors review evidence that lower rates of exercise and sun-exposure, common in Western lifestyles, have also been found to be related to postpartum depression.[25] However, evidence is mixed.[26] These hypotheses would be easy to test in randomized controlled trials, in which supplementary exercise and Vitamin D could be administered to test samples. However, evidence from direct trials is also mixed.[27]

One of the more commonly cited mismatch hypotheses relates to changes in family networks and childcare routines. Hunter-gatherer families often live with their extended families and regularly share childcare duties, whereas Western families may live very far from their relatives and therefore must meet the demands of childcare themselves. This likely causes additional stress and anxiety in new parents, who do not have access to assistance from their family members. This aspect of the hypothesis is more difficult to test, as the relationship between family assistance and postpartum depression is likely more complicated.

Psychological pain hypothesis

Others have focused on the crux of reproductive decision-making in humans, which is twofold.[28] First there exists a tradeoff between present and future offspring. In life-history theory, organisms have limited reproductive energy which requires that trade-offs be made when choosing to invest in one infant over another or over additional mating opportunities. Secondly, there is a tradeoff between the quantity and quality of offspring.[29]

Because women's reproduction is more constrained than men's by obligate energetic demands, women experience higher risks relative to decisions to invest or not invest. As such, a mechanism which served to signal to women that they faced a bad investment opportunity, would be evolutionarily adaptive. For instance, in modern, industrialized societies where mortality is low, parents are incentivized to invest more per child than parents who live in less stable environments or utilizing riskier subsistence strategies.[30] See life history theory.

For example, Bereczkei et al. found that women in Hungary with higher rates of low birth-weight infants had shorter inter-birth intervals, corresponding to an additional 2–4 years of potential reproduction.[31] These women had significantly more children by the end of their reproductive careers than women who did not have low birth-weight children, pointing to a tradeoff between offspring quantity and quality.

In this vein, some researchers hypothesized that postpartum depression is more likely to occur in mothers who are suffering a fitness cost, in order to inform them that they should reduce or withdraw investment in their infants.[32][33] Support for this hypothesis was found in a population of hunter-horticulturalists, the Shuar, located in the Ecuadorian Amazon.[34] Reasons for this could include lack of paternal or other social support, poor infant health, or birth complications, all of which are commonly associated with postpartum depression. Hagen also found support that postpartum depression could function as a bargaining strategy, in which parents who were not receiving adequate support from their partners withdrew their investment in order to elicit additional support. In support of this, Hagen found that postpartum depression in one spouse was related to increased levels of child investment in the other spouse. Furthermore, support was also found for a reduction in rates of postpartum depression for older women with few future reproductive opportunities.[35] Another study reported similar findings.[36]

Can PPD be adaptive and related to reduced fertility?

There is undoubtedly a reproductive cost to experiencing postpartum depression which likely affects future reproductive strategies and child-spacing decisions. Specifically, Myers et al. found that women who experienced postpartum depression with their first or second birth had reduced likelihood of parity progression to a third birth, and lower completed fertility overall.[37] Given this, how do adaptationist hypotheses explain postpartum depression? Hagen and Thornhill, for one, argue that limiting complete family size is one method of reducing parental investment in poor circumstances.[38] Furthermore, they found evidence that poor maternal condition at birth one was highly correlated with poor condition at subsequent births, as such it could be the poor condition, not postpartum depression that drives lower fertility.

Cross-cultural variation in postpartum depression

Cross-cultural rates of peri- and postpartum depression are difficult to interpret, as differences in cultural expressions of depression may lead to inaccurate diagnosis. The majority of screening instruments that test for peri- and postpartum depression were designed in Western contexts and as such emphasize symptoms that are common in Western countries.[7] Studies have found that women in Asia tend to report more somatic symptoms during depressive episodes, including feeling head numbness. Affective symptoms, such as feelings of sadness and guilt, are more commonly reported in Western samples than in Hispanic, Asian, and African cultures. One of the most commonly used screening instruments for postpartum depression, the Edinburgh Postnatal Depression Scale, does not detect depression in Japanese women.[39]

Early research returned mixed evidence regarding cross-cultural rates of postpartum depression. One review found similar rates of postpartum mental disorders across countries.[40] In a more recent meta-analysis including 143 studies with data from samples around the world, rates of PPD varied between 0 and 60%.[7] Another meta-analysis found rates of postpartum depression returned from self-reported questionnaires to vary from 1.9% to 82.1% in developing countries and from 5.2% to 74.0% in developed countries. Rates were much lower when structured clinical interviews used, yet still varied from 0.1% in Finland to 26.3% in India.[41]

The reasons for these discrepancies are not fully understood, however, it may be that the often reported rates of postpartum depression of around 15% do not reflect true rates of postpartum depression experienced by women around the world. Variation may be due to differences in measurement techniques, socio-economic factors, symptom expression, or cultural factors relating to pregnancy and childbirth.

There is some evidence that cultures which designate an explicit postpartum period, in which new mothers are expected to rest and receive assistance from family and friends, have lower rates of postpartum depression.[42] However, other studies have not found this effect.[22]

Evolutionary approaches to postpartum depression offer frameworks that can be informative, even given these variations in rates of postpartum depression. Because evolutionary medicine explores causality and treatment from the perspective of universal human biology and psychology, these approaches may bring to light new perspectives on causes and treatments.

See also

References

  1. ↑ 1.0 1.1 "Postpartum Depression". http://www.apa.org/pi/women/resources/reports/postpartum-depression.aspx. 
  2. ↑ "Postpartum psychosis: detection of risk and management". The American Journal of Psychiatry 166 (4): 405–8. April 2009. doi:10.1176/appi.ajp.2008.08121899. PMID 19339365. 
  3. ↑ "A review of postpartum psychosis". Journal of Women's Health 15 (4): 352–68. May 2006. doi:10.1089/jwh.2006.15.352. PMID 16724884. 
  4. ↑ "Perinatal depression: a systematic review of prevalence and incidence" (in en-US). Obstetrics and Gynecology 106 (5 Pt 1): 1071–83. November 2005. doi:10.1097/01.AOG.0000183597.31630.db. PMID 16260528. 
  5. ↑ Perinatal Depression: Prevalence, Screening Accuracy, and Screening Outcomes: Summary. Agency for Healthcare Research and Quality (US). 2005. https://www.ncbi.nlm.nih.gov/books/NBK11838/. 
  6. ↑ "The prevalence of postpartum depression: the relative significance of three social status indices". Social Psychiatry and Psychiatric Epidemiology 42 (4): 316–21. April 2007. doi:10.1007/s00127-007-0168-1. PMID 17370048. 
  7. ↑ 7.0 7.1 7.2 "Cross-cultural and social diversity of prevalence of postpartum depression and depressive symptoms". Journal of Affective Disorders 91 (2–3): 97–111. April 2006. doi:10.1016/j.jad.2005.12.051. PMID 16466664. 
  8. ↑ "Paternal postpartum depression, its relationship to maternal postpartum depression, and implications for family health". Journal of Advanced Nursing 45 (1): 26–35. January 2004. doi:10.1046/j.1365-2648.2003.02857.x. PMID 14675298. 
  9. ↑ 9.0 9.1 "Correlates of ante- and postnatal depression in fathers: a systematic review". Journal of Affective Disorders 130 (3): 358–77. May 2011. doi:10.1016/j.jad.2010.06.019. PMID 20599275. 
  10. ↑ "Prenatal and postpartum depression in fathers and its association with maternal depression: a meta-analysis". JAMA 303 (19): 1961–9. May 2010. doi:10.1001/jama.2010.605. PMID 20483973. 
  11. ↑ Foli, Karen J.; Gibson, Gregory C. (1 May 2011). "Sad Adoptive Dads: Paternal Depression in the Post-Adoption Period". International Journal of Men's Health 10 (2): 153–162. doi:10.3149/jmh.1002.153. ProQuest 896662625. 
  12. ↑ "Risk factors for depressive symptoms during pregnancy: a systematic review". American Journal of Obstetrics and Gynecology 202 (1): 5–14. January 2010. doi:10.1016/j.ajog.2009.09.007. PMID 20096252. 
  13. ↑ "A systematic review and meta-analysis of the association between unintended pregnancy and perinatal depression". Journal of Affective Disorders 192: 56–63. March 2016. doi:10.1016/j.jad.2015.12.008. PMID 26707348. 
  14. ↑ "Domestic violence and perinatal mental disorders: a systematic review and meta-analysis". PLOS Medicine 10 (5): e1001452. 2013-05-28. doi:10.1371/journal.pmed.1001452. PMID 23723741. 
  15. ↑ "Antenatal risk factors for postpartum depression: a synthesis of recent literature". General Hospital Psychiatry 26 (4): 289–95. 2004-07-01. doi:10.1016/j.genhosppsych.2004.02.006. PMID 15234824. 
  16. ↑ "Prevalence and determinants of common perinatal mental disorders in women in low- and lower-middle-income countries: a systematic review". Bulletin of the World Health Organization 90 (2): 139G–149G. February 2012. doi:10.2471/BLT.11.091850. PMID 22423165. 
  17. ↑ "Biological and psychosocial predictors of postpartum depression: systematic review and call for integration". Annual Review of Clinical Psychology 11 (1): 99–137. 2015. doi:10.1146/annurev-clinpsy-101414-020426. PMID 25822344. 
  18. ↑ "Placental Corticotropin-Releasing Hormone Mediates the Association Between Prenatal Social Support and Postpartum Depression". Clinical Psychological Science 1 (3): 253–264. July 2013. doi:10.1177/2167702612470646. PMID 23997996. 
  19. ↑ "Prevalence and risk factors for postpartum depression among women with preterm and low-birth-weight infants: a systematic review". BJOG 117 (5): 540–50. April 2010. doi:10.1111/j.1471-0528.2009.02493.x. PMID 20121831. 
  20. ↑ Beck, Cheryl Tatano (September 2001). "Predictors of Postpartum Depression: An Update". Nursing Research 50 (5): 275–85. doi:10.1097/00006199-200109000-00004. PMID 11570712. 
  21. ↑ "Perinatal depression: prevalence, risks, and the nutrition link--a review of the literature". Journal of the American Dietetic Association 109 (9): 1566–75. September 2009. doi:10.1016/j.jada.2009.06.368. PMID 19699836. 
  22. ↑ 22.0 22.1 "Postpartum depression in Asian cultures: a literature review". International Journal of Nursing Studies 46 (10): 1355–73. October 2009. doi:10.1016/j.ijnurstu.2009.02.012. PMID 19327773. 
  23. ↑ 23.0 23.1 "Is Postpartum Depression a Disease of Modern Civilization?". Current Directions in Psychological Science 23 (6): 395–400. December 2014. doi:10.1177/0963721414547736. PMID 28503034. 
  24. ↑ "Seafood consumption, the DHA content of mothers' milk and prevalence rates of postpartum depression: a cross-national, ecological analysis". Journal of Affective Disorders 69 (1–3): 15–29. May 2002. doi:10.1016/S0165-0327(01)00374-3. PMID 12103448. 
  25. ↑ "Low maternal serum vitamin D during pregnancy and the risk for postpartum depression symptoms". Archives of Women's Mental Health 17 (3): 213–9. June 2014. doi:10.1007/s00737-014-0422-y. PMID 24663685. http://research-repository.uwa.edu.au/en/publications/low-maternal-serum-vitamin-d-during-pregnancy-and-the-risk-for-postpartum-depression-symptoms(8b789319-93b6-4ab0-b2c6-50f2b57fda4e).html. 
  26. ↑ "Vitamin D status during pregnancy and the risk of subsequent postpartum depression: a case-control study". PLOS ONE 8 (11): e80686. 2013-11-27. doi:10.1371/journal.pone.0080686. PMID 24312237. Bibcode: 2013PLoSO...880686N. 
  27. ↑ "The role of exercise in treating postpartum depression: a review of the literature". Journal of Midwifery & Women's Health 52 (1): 56–62. 2007. doi:10.1016/j.jmwh.2006.08.017. PMID 17207752. 
  28. ↑ Kaplan, Hillard S.; Lancaster, Jane B. (2003). An Evolutionary and Ecological Analysis of Human Fertility, Mating Patterns, and Parental Investment. National Academies Press (US). https://www.ncbi.nlm.nih.gov/books/NBK97292/. 
  29. ↑ Smith, Christopher C.; Fretwell, Stephen D. (July 1974). "The Optimal Balance between Size and Number of Offspring". The American Naturalist 108 (962): 499–506. doi:10.1086/282929. 
  30. ↑ Kaplan, Hillard (1996). "A theory of fertility and parental investment in traditional and modern human societies". American Journal of Physical Anthropology 101 (S23): 91–135. doi:10.1002/(sici)1096-8644(1996)23+<91::aid-ajpa4>3.0.co;2-c. 
  31. ↑ "Low birth weight, maternal birth-spacing decisions, and future reproduction : A cost-benefit analysis". Human Nature 11 (2): 183–205. June 2000. doi:10.1007/s12110-000-1018-y. PMID 26193366. 
  32. ↑ Hagen, Edward H (September 1999). "The Functions of Postpartum Depression". Evolution and Human Behavior 20 (5): 325–359. doi:10.1016/S1090-5138(99)00016-1. 
  33. ↑ Thornhill, Randy; Furlow, Bryant (1998). "Stress and Human Reproductive Behavior: Attractiveness, Women's Sexual Development, Postpartum Depression, and Baby's Cry". Stress and Behavior. Advances in the Study of Behavior. 27. pp. 319–369. doi:10.1016/S0065-3454(08)60368-X. ISBN 978-0-12-004527-3. 
  34. ↑ Hagen, Edward H.; Barrett, H. Clark (March 2007). "Perinatal Sadness among Shuar Women: Support for an Evolutionary Theory of Psychic Pain". Medical Anthropology Quarterly 21 (1): 22–40. doi:10.1525/maq.2007.21.1.22. PMID 17405696. 
  35. ↑ Hagen, Edward H (September 2002). "Depression as bargaining". Evolution and Human Behavior 23 (5): 323–336. doi:10.1016/S1090-5138(01)00102-7. 
  36. ↑ "Reappraising the relationship between maternal age and postpartum depression according to the evolutionary theory: Empirical evidence from a survey in primary health services". Journal of Affective Disorders 142 (1–3): 219–24. December 2012. doi:10.1016/j.jad.2012.04.030. PMID 22840607. 
  37. ↑ "Postnatal depression and reproductive success in modern, low-fertility contexts". Evolution, Medicine, and Public Health 2016 (1): 71–84. 2016. doi:10.1093/emph/eow003. PMID 26976787. 
  38. ↑ "Testing the psychological pain hypothesis for postnatal depression: Reproductive success versus evidence of design". Evolution, Medicine, and Public Health 2017 (1): 17–23. 2017. doi:10.1093/emph/eow032. PMID 28073826. 
  39. ↑ Bashiri, Nasrin; Spielvogel, Anna M (1999-05-01). "Postpartum depression: a cross-cultural perspective". Primary Care Update for OB/GYNS 6 (3): 82–87. doi:10.1016/S1068-607X(99)00003-7. 
  40. ↑ "Postnatal mental illness: a transcultural perspective". Social Psychiatry and Psychiatric Epidemiology 29 (6): 250–64. November 1994. doi:10.1007/BF00802048. PMID 7825036. 
  41. ↑ "Magnitude and risk factors for postpartum symptoms: a literature review". Journal of Affective Disorders 175: 34–52. April 2015. doi:10.1016/j.jad.2014.12.041. PMID 25590764. 
  42. ↑ "Traditional postpartum practices and rituals: a qualitative systematic review". Women's Health 3 (4): 487–502. July 2007. doi:10.2217/17455057.3.4.487. PMID 19804024. 



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