associated with increased costs to the mother—colicky babies can be exhausting. Poor infant
temperament should therefore also be significantly correlated with PPD. In a meta-analysis of
17 studies on the relationship between infant temperament and PPD, Beck (1996a) found a
significant correlation of moderate effect size.
Prediction 3: poor environments should predict negative affect
If mothers do not have sufficient resources to raise a new infant or the environment is
exceptionally hazardous, they should consider defecting, saving their investment for existing or
future offspring, or for their own health and welfare. Low levels of resources or a hazardous
environment should therefore predict negative affect postpartum. Because it is not clear how
modern environmental stressors such as poverty and crime relate to environmental stressors of
ancestral environments, this paper will not closely examine these variables. Nevertheless, some
evidence supports the association of poverty and poor environments with PPD. Although most
studies find little or no correlation of PPD with socioeconomic status (SES) or other
demographic variables (Cutrona, 1982; O’Hara & Zekoski, 1988), this is probably because
subjects are obtained from fairly homogenous middle class populations. In those few studies
specifically examining financially impoverished populations, rates of PPD are significantly
elevated (Hobfoll, Ritter, Lavin, Hulsizer & et al., 1995; Seguin, Potvin, St.-Denis & Loiselle,
1995; Zelkowitz & Milet, 1995).
More specifically, Warner et al (1996) found both maternal unemployment and “Head of
household” unemployment to be significant risk factors for PPD (OR = 1.56 & 1.50
respectively). Finally, in a large study, Cooper et al (1996) report that 7% of mothers with
PPD were dissatisfied with the area they were living in (prepartum) compared to only 3% of
nondepressed mothers. Thus, poor environments do appear to predict negative affect
postpartum.
Prediction 4: PPD should be universal
If PPD is an adaptation, then all women in all cultural contexts should experience PPD if
circumstances warrant. This does not imply that PPD should be found in all societies, however.
If, in some particular society, all women receive sufficient social support, do not face social
costs for defecting from low viability offspring, and otherwise incur few costs when raising
offspring, then rates of PPD should be extremely low. Nevertheless, if PPD is rarely
encountered in non-Western populations, or if it is not correlated with low levels of social
support or low infant viability, then the adaptationist account offered here is seriously
undermined. Some women in most societies should face the problem of insufficient social
support, deciding whether to invest in low viability offspring, etc. These problems are
inevitable, and it is unlikely that most societies will have solved these problems to the complete
satisfaction of all mothers.
Although studies of PPD in populations other than middle class, Caucasian Americans and
British are few, the syndrome has been identified in a number of different ethnic contexts (see
table 4 for a summary of cross-cultural studies of PPD). As required by the defection
hypothesis, PPD does correlate with low levels of social support (Areias, Kumar, Barros &
Figueiredo, 1996; Ghubash & Abou-Saleh, 1997; Thorpe, Dragonas & Golding, 1992; Yoshida,
Marks, Kibe, Kumar & others, 1997) and low infant viability (Ghubash & Abou-Saleh, 1997;
Yoshida et al., 1997). Unfortunately, studies in small, kin-based societies that are most likely to
resemble ancestral social environments are essentially non-existent.
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