Chapter 2 52 observations to the never depressed group, but if she were subsequently diagnosed with a depressive disorder she would contribute her next measurement to the depressed group-observations, and if she next would recover from the depressive disorder her next measurement would be grouped into the remitted group. 2.5. Statistical analyses Statistical analyses were conducted using R (version 3.6.1; R Core Team, 2020). Demographic differences between the measurement groups were analyzed with Chi square tests for categorical variables and t-tests for continuous variables. To analyze associations between OC use and symptoms of depression or insomnia, all outcomes were compared using (generalized) linear mixed models. Models were created using the ‘lme4’ package (Barr, 2013), and analyzed with ANOVA tests (type 3) from the ‘car’ package (Fox & Weisberg, 2020). Model estimates were estimated using the ‘summary’ function from the R package lmerTest (Kuznetsova et al., 2017) using an unstructured variance-covariance structure. In all models, a random intercept per participant was added to account for multiple measures within the same participants. This random intercept also enabled within-participant comparisons between OC and NC measurements in a subset of the measurements. Generalized linear (logistic) mixed models were used for analysis of categorical outcomes (e.g., diagnoses of MDD and dysthymia) and linear mixed models were used for the continuous variables (e.g. IDS scores, WHI-IRS scores, IDS atypical depression subscores). 2.5.1. Univariable model and multivariable model First, outcomes were assessed using a univariable model that included only the contraceptive status (e.g., OC status or NC status at time of measurement) as fixed or independent variable and MDD or dysthymia diagnoses, depressive symptom scores (including atypical depressive symptoms) or insomnia symptom score as outcomes. Second, we used a multivariable model with adjustment for previously mentioned confounders to estimate differences between OC and NC measurements in all outcomes (e.g., MDD and dysthymia diagnoses, depressive symptoms, atypical depressive symptoms and insomnia symptoms).
RkJQdWJsaXNoZXIy MTk4NDMw