How Birth Control Pills Affect the Female Brain

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Birth control pills have been on the market for almost 60 years now and are used by almost 200 million women worldwide. Particularly, the use of birth control pills increases among adolescents. However, the effects of birth control pills on the brain have widely been ignored. It was my own research that found the first indication that birth control pills affect female brain structure and masculinize female brain function. Furthermore, I recently obtained evidence that these changes are strongly dependent on the type of synthetic hormone contained in birth control pills and might affect some brain areas, like the hippocampus, beyond the duration of contraceptive treatment. This poses the question, whether effects of birth control pills on the brain are fully reversible after women stop taking the pill, especially if pill use occurs during sensitive periods of brain development, like in adolescents. Previous studies suffer from small sample sizes and insufficient study designs. Importantly, they compare women on birth control pills to naturally cycling women (cross-sectional designs) rather than following the same women from before she starts taking the pill through the first months of her pill use and vice versa (longitudinal designs). Accordingly they may be confounded by sampling bias. Therefore the general aims of this proposal are (A) to study the effects of birth control pills on the brain – for the first time – systematically in a longitudinal design, and (B) to address whether the effects of birth control pills on the brain are fully reversible. I seek to link changes in the brain to changes in behaviour, and address whether different types of pills cause different effects. Most importantly, a specific focus will lie on teen use of birth control pills. In order to address these questions, this project will employ a multi-modal imaging design, following several groups of pill users over multiple time-points before, during and after contraceptive treatment.