Published in April in the journal “Human Brain Mapping,” the study measured cortical thickness in the brains of 90 women – 44 of whom were using oral contraceptives, and 46 of whom were naturally cycling.
Only women using the combination form of oral contraceptives were used in the study – it did not measure women using progesterone-only or other forms of oral contraceptives. The research found that oral contraceptive use was significantly associated with a thinning in two areas of the brain: the lateral orbitofrontal cortex and the posterior cingulate cortex.
The lateral orbitofrontal cortex is involved in emotion regulation and response to rewards, while the posterior cigulate cortex regulates inward-directed thought, such as recalling personal memories or planning for the future.
“You might think after 50 years and hundreds of millions of women taking various incarnations of the pill, there would be a large and cohesive and impressive body of evidence on it, but there’s next to nothing,” Cahill told CNA. “I honestly find that amazing.”