OC, depressive and insomnia symptoms in adult women with and without depression 61 disorder, meaning our results can be well-generalized to women with a vulnerability for depressive disorders. As depression is common in society, this helps to generalize results to the broader population. We were able to also assess interaction effects of OC with a history of depressive disorders, which has rarely been done before. Second, psychiatric diagnoses were assessed prospectively using validated clinical interviews as well as selfreported depressive symptoms. This is fairly unique, since many studies on OC and depression rely only on self-reported depressive symptoms and retrospective questions about previous diagnoses of depression. Third, as we excluded women who breastfed, gave birth in the past year or had an abnormal cycle length, hormonal abnormalities related to pregnancy, breastfeeding or menopause did most likely not affect the analyses. Fourth, the repeated measurements within the same participants enabled withinperson comparisons between OC and NC measurements within the same person, which have evidently provided novel insights into the association between OC and depression. This study has limitations in other aspects. These limitations lie mostly in the domain of OC assessment, since the NESDA cohort originally was not aimed to assess OC use. We did not have information on the age of first use of OC, nor on the duration of current OC use. This limited the study in two ways. Firstly, recent studies found that OC use during adolescence could increase the likelihood of a depression diagnosis in adulthood, even if women did not use OC anymore (Anderl et al., 2020; Zettermark et al., 2018). The current study, however, could not take previous OC use during adolescence into account. Additionally, we only had data on concurrent OC use, meaning we did not have data on recency of OC use. We used 6 month-latency of diagnoses of MDD and dysthymia, meaning a participant could hypothetically have been depressed before they started OC use. As a consequence of these limitations we were unable to investigate exact causal relationships between OC use and depressive disorders. Furthermore, the composition or brand and dosage of the used OC and duration of use was unknown. Previous studies, such as Skovlund et al. (2016) found that progestin-only contraceptives were more strongly associated with depressive disorders than combined contraceptives. In the Netherlands, 95.8% of women use a form of combined oral contraceptives, with both estradiol and progesterone in its formulation. Moreover, ethinylestradiol/levonorgestrel 0.03/0.15 mg (or “Microgynon 30”) is the
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