How Birth Control Pills affect the Female Brain

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, even though mood changes due to contraceptive use are a long known side effect. Ten years ago, we found the first indication that birth control pills affect female brain structure and masculinize female brain function. Furthermore, recent evidence suggests 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 and basal ganglia, 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 contraceptive treatment occurs during sensitive periods of brain development, like adolescence.
Previous studies suffer from small sample sizes and may be confounded by sampling bias, because they employ cross-sectional designs, i.e. compare women on birth control pills to naturally cycling women. In order to be certain that changes are related to pill use, studies need to follow the same women from before they start taking the pill through the first months of their pill use and vice versa (longitudinal designs).
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 after discontinuation of contraceptive treatment. The project seek to link changes in the brain to changes in behaviour, and addresses 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 timepoints before, during and after contraceptive treatment.