rates did not control for marital status. The 1-year prevalence rates of major depression in
community samples among married women is much lower (2.1%) than among divorced women
(6.3%) (Weissman, Bruce, Leaf, Florio & Holzer, 1991). Since most postpartum women are
married, controlling for marital status would likely increase the difference between the baseline
rate and the rate postpartum, increasing the probability that PPD is causally related to
childbirth.
The best controlled study of prevalence rates (Cox, Murray & Chapman, 1993) found no
significant differences between postpartum depressed women and women in a control group in
either point prevalence at six months postpartum or six-month prevalence rates (see also
Campbell and Cohn, 1991; O’Hara et al., 1990), but did find that the rate of onset was three
times higher for the postnatal group versus the control group within five weeks of childbirth.
Therefore, the available evidence supports the conclusion that at least some cases of depression
postpartum are non-randomly associated with parturition, though this issue clearly warrants
further study.
Tests of the Defection Hypothesis for postpartum depression
Prediction 1: lack of social support should predict negative affect
Lack of “support” from the spouse, family, and others is strongly correlated with PPD, a
result that has been replicated in numerous studies. The correlation of lack of spousal support
with PPD is virtually undisputed (see table 1), and holds regardless of whether PPD is assessed
by symptom levels from self-report instruments or clinical diagnosis (correlations with clinical
diagnoses of PPD are marked with an asterisk*).
A causal relationship between marital satisfaction and PPD in women is supported by
O’Hara’s study of depressive symptomology and marital satisfaction in 51 couples (O’Hara,
1985). In this study, 18.0% of the women and 7.8% of the men had symptoms of at least mild
depression at six weeks postpartum. The depression and marital satisfaction scores obtained
from the husbands’ at 6 weeks were excellent predictors of their wives’ depression and marital
satisfaction scores obtained three weeks later. If the father’s scores are an indication of his
ability or willingness to invest in childrearing (as is true for mothers; see below), then these
data support a causal relation between paternal support and maternal PPD.
The etiological significance of marital satisfaction is also supported by Gotlib, et al.’s
prospective study of PPD among a sample of 730 pregnant women (Gotlib et al., 1991).
Woman who were not depressed during pregnancy but became depressed postpartum were
distinguished from those that did not become depressed postpartum by lower marital
satisfaction during pregnancy. It should be emphasized that the difference in marital
satisfaction scores was obtained before the onset of depression, when all women in the
subsample were not depressed—marital discord preceded the onset of depression. This study
also assessed factors involved in the postpartum recovery from depression experienced during
pregnancy. Of the women who were depressed during pregnancy, those who recovered
postpartum reported significantly greater postpartum marital satisfaction. Similarly, Campbell
et al. (1992) found high levels of help from spouses and better interactions with infants to be
the only variables associated with remission of PPD.
The defection hypothesis in particular is supported by the study of Field, et al. (1985) where
a simple questionnaire was administered to a large number of women in the third trimester (see
figure 1). Questions one to three address the availability and reliability of paternal investment,
while questions four to six address the value of the pregnancy to the mother. These are
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