these correlations do not appear to depend strongly on making a distinction between depressive
symptomology and clinical diagnosis. Unfortunately, pregnancy, delivery, and infant
complications are presented as aggregate scores, so the correlation of any particular problem
with PPD cannot be determined from the literature.
In Hopkins et al’s study (1987), infants of depressed mothers had experienced significantly
greater incidence of neonatal complications than infants of nondepressed mothers (32% v.
4%). O’Hara, et al. (1984) found that although a general measure of life events was not a
significant predictor of PPD, childcare related stressors (e.g., baby health problems) and
obstetric risk factors accounted for 19% of the variance in depressive symptomology.
In Campbell and Cohn’s study (1991) of over a thousand primiparous middle class mothers
of healthy full term infants, the depressed group reported significantly more complications
during pregnancy or delivery than the nondepressed group. A high correlation between
pregnancy and delivery problems, and depression in mothers of apparently healthy infants a
month or more later is strong evidence for the defection hypothesis. When studies that include
only mothers of healthy infants show strong correlations between pregnancy problems and
PPD, it implies that this relationship may be due to the existence of a neurophysiological link
between these indicators of lowered infant viability and PPD that is independent of the
mother’s subjective evaluation. This type of functional specialization is a hallmark of
adaptation (Williams 1966).
Male PPD also appears to be associated with infant variables in the direction predicted by
the defection hypothesis. Atkinson and Rickel (1984) found that, controlling for prepartum
BDI scores, father’s postpartum BDI scores were significantly negatively correlated with the
perception that the infant was “better than average.” Male PPD was also correlated with
prepartum expectations of a better than average infant. Thus, men who, prepartum, expected
their infants to be above average, but, postpartum, felt their infants to be below average were
the most likely to be depressed.
Not all studies support associations with infant problems and PPD (e.g., Paykel, Emms,
Fletcher & Rassaby, 1980), and some support an association between less complicated
deliveries and PPD (O’Hara et al., 1982; Paykel et al., 1980). The authors of these studies
suggest this could be the result of additional support received by mothers with very complicated
deliveries from doctors and family members. If doctors, nurses, and other hospital staff assume
most of the costs of caring for a seriously impaired infant, while they and family members also
provide the mother with high levels of support, the mother’s very low costs may not exceed her
benefits, and she will therefore have little reason to experience PPD. These last two studies
notwithstanding, there is clear evidence that both infant problems and reliable indicators of
infant problems are significantly associated with PPD.
Poor infant temperament, usually categorized as an “infant problem” in most studies of
PPD, is not an indicator of decreased infant viability (to my knowledge). However, it is
attempt to extract additional resources from the mother in order to increase its odds of survival when it has
information that it is damaged in some way (still assuming a conflict between maternal and paternal genes, of
course). This hypothesis would account for the association between gestational diabetes and hypertension, and
higher rates of infant morbidity and mortality. Under this scenario, the morbidity and mortality data for these
disorders support the defection hypothesis.
In addition to being a significant predictor of child morbidity and mortality, pregnancy induced hypertension
is a leading cause of maternal death (Grimes, 1994; Li, Fortney, Kotelchuck & Glover, 1996; Ni & Rossignol,
1994; Walker, 1996). The apparent association of pregnancy induced hypertension with PPD may therefore also
be evidence in favor of prediction 4 above: it may be in the mother’s interest to invest in her own survival and
development rather than the infant. This prediction will not be tested further due to lack of data.
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