Statistical Analyses
We performed a nested case-control study from the IGEDEPP cohort. We
identified 250 cases of early PPD, defined as meeting DSM-5 criteria for
major depressive episode at the 8 week interview. Similarly, there were
235 cases of late PPD, identified at the one-year visit. Categories were
mutually exclusive, participants with early PPD were not considered as
having late PPD even if they met criteria for PPD at the one-year visit.
Women without any form of perinatal depression (i.e. neither during
pregnancy nor in the first year postpartum) were used as unmatched
controls (N=2726).
Descriptive statistics for binary and categorical variables included
sample sizes and percentages for each category and according to the
case/control status. Multivariable logistic regressions were conducted
to quantify the association between PPD and associated factors at a
given time point. Odds-ratios (ORs), adjusted for socio-demographic
variables (i.e. age, marital status, education level, and employment),
are reported along with their 95% confidence interval (CI) and
p-values. The significance threshold was set at .05. Socio-demographic
variables and variables with a p-value below 0.2 in the first analysis
were included as adjustment factors for the multivariable model, using
stepwise variable selection to optimize the Akaike information criterion
(AIC). All analysis were performed with R, v3.6.1.
RESULTS