Women who began taking oral contraceptives as adults had a 92% higher rate of depressive symptoms compared to those who never took the pill, while women who started taking the birth control pill “before or at the age of 20 had 130% higher rate of depressive symptoms,” according to a U.K. study published Monday by Cambridge University Press.
Except the authors even admit that there is a selection bias inherent in the study:
This study highlights the importance of considering the healthy user bias as well as family-level confounding in studies of OC [oral contraceptive] use and mental health outcomes.
Healthy user bias in this study is used to describe the behavior that those who have negative outcomes on OC cease using OC.
Other uses of the term healthy user bias within this study:
Research on the effect of oral contraceptive (OC) use on the risk of depression shows inconsistent findings, especially in adult OC users. One possible reason for this inconsistency is the omission of women who discontinue OCs due to adverse mood effects, leading to healthy user bias.
Similar underestimation of effects can be seen in observational studies not considering previous OC use, as exemplified in the Netherlands Study of Depression and Anxiety cohort, which found that current OC use in a between-person analysis was associated with lower risk of depression, while the within-analysis showed that the time during OC use was associated with an increased risk of depression. This discrepancy is likely explained by a healthy user bias as those negatively affected by OC use had discontinued and thus represented nonusers in the between-person analysis (Morssinkhof et al., Reference Morssinkhof, Lamers, Hoogendoorn, de Wit, Riese, Giltay, van den Heuvel, Penninx and Broekman2021).
This sentence you’re quoting indicates the exact opposite of what you’ve attributed it to.
