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Birth Control Pills Shrink Women’s Brains

By Eowyn @DrEowyn

Studies have shown that oral contraceptives or birth control pills put women at enhanced risk for glaucoma and multiple sclerosis.

Now add brain shrinkage to the list.

A new study out of UCLA found that the birth control pill may thin areas in a woman’s brain and affect their functions in regulating emotional reaction and future planning.

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.


The research study by Nicole Petersen, Alexandra Touroutoglou, Joseph M. Andreano and Larry Cahill, “Oral contraceptive pill use is associated with localized decreases in cortical thickness,” was published in April 2015 in the journal Human Brain Mapping. Here’s the abstract:

Oral contraceptive pills (OCs), which are used to prevent pregnancy by the majority of women in the United States, contain steroid hormones that may affect the brain’s structure and function. In this investigation, we tested the hypothesis that OC use is associated with differences in brain structure using a hypothesis-driven, surface-based approach. In 90 women, (44 OC users, 46 naturally-cycling women), we compared the cortical thickness of brain regions that participate in the salience network and the default mode network, as well as the volume of subcortical regions in these networks. We found that OC use was associated with significantly lower cortical thickness measurements in the lateral orbitofrontal cortex and the posterior cingulate cortex. These regions are believed to be important for responding to rewards and evaluating internal states/incoming stimuli, respectively. Further investigations are needed to determine if cortical thinning in these regions are associated with behavioral changes, and also to identify whether OC use is causally or only indirectly related to these changes in brain morphology.

Although the study only measured brain structure, the findings suggest that there could be possible effects on behavior.

Nicole Petersen

According to Catholic World Report, May 15, 2015, Dr. Nicole Petersen, a neuroscientist at UCLA and the study’s lead author, noted that “Some women experience negative emotional side effects from taking oral contraceptive pills, although the scientific findings investigating that have been mixed. So it’s possible that this change in the lateral orbitofrontal cortex may be related to the emotional changes that some women experience when using birth control pills.

Larry Cahill

Since the UCLA study is one of the first of its kind in measuring effects of the birth control pill on brain structure, it’s difficult for scientists to draw any definite conclusions at this point. But Dr. Larry Cahill, a professor of neurobiology and behavior at the University of California-Irvine and a co-author of the study, said he’s amazed at the lack of research considering how long the pill has been on the market: “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. I honestly find that amazing.”

Although Cahill cautioned against a panic or alarm because of the recent study, he said it raises further questions for research that are important to the millions of women who use oral contraceptives every day. For example, follow-up studies are needed to determine whether the thinning effect is permanent, or whether it just occurs if a woman is currently using the pill.

In April 2011, Cahill and three other researchers found that the emotional memory of women using hormonal contraception was more similar to that of men than of women. Combined with the evidence of the most recent study, Cahill said one group that might benefit from the pill’s possible impact on emotional memory could be women in combat or other traumatic situations. If using hormonal contraception, these women could be potentially less likely to develop post-traumatic stress disorder than naturally cycling women in similar situations, though more research is needed.

Dr. Cahill said these studies are part of a growing body of research on sex differences in the brain, which is challenging the long-held assumption that men and women are mostly biologically the same, save for their reproductive organs: “We’re all blinded by our assumptions, and there’s simply been an assumption…that any differences between (men and women) occur in the bikini zone and that’s it. And now we’re realizing, well, no. There’s sex differences all over the place. It’s important that we stop assuming that women are just men with pesky hormones.”

Cahill also said that he and his fellow researchers, by challenging established assumptions (otherwise called “prejudice”), have experienced “road blocks” in trying to publish their findings, because they are often dismissed as being “alarmist.” However, he believes that as a scientist, it’s important to continue to study the potentially good, bad or neutral effects of a medication that millions of women use for large portions of their life. He said:

“If I’m a woman on the pill, or I know a woman who’s on the pill…or I have a daughter who wants to go on the pill, you want to operate from knowledge, not from complete lack of knowledge. That was the goal, to explore what the pill might be doing just as we’ve been doing for 3 or 4 years.”

See also:

  • Women who took birth control pills for more than 3 years double the risk of glaucoma
  • Birth control pills linked to 30% increased risk of multiple sclerosis
  • Birth control pills and other chemicals producing intersex Franken-fish


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