The pill is a very popular contraceptive choice for women, with around 100 million individuals worldwide currently using it. There is no doubt that it has helped revolutionize contraception, and most users report satisfaction, but it is also apparent that it can cause undesirable side effects in women. For example, many studies have demonstrated that its use is associated with metabolic and emotional effects, and one study even found it could influence a woman’s choice of partner.
Now, a new investigation is adding to the growing body of evidence that the pill may be associated with neurological alterations, with the discovery that oral contraceptives are linked to thinning in two different regions of the brain, possibly altering their function.
For the study, scientists at the University of California, Los Angeles (UCLA), investigated 90 women, 44 of whom were using oral contraceptives, whilst the others were naturally-cycling. They were interested in comparing the thickness and volumes of different brain regions that participate in two networks, the salience network and the default mode network. The former functions to sort through all the internal and external stimuli we are presented with, like pain or a distant noise, in order to identify the most relevant for guiding behavior. The latter is most active when we are at rest, for example during daydreaming or thinking about the future.
As described in Human Brain Mapping, the researchers found that two particular regions, the lateral orbitofrontal cortex and the posterior cingulate cortex, tended to be thinner in those who were taking oral contraceptive pills. The lateral orbitofrontal cortex helps us regulate emotions and is thought to allow us to adapt our behavior in response to rewards or adversities, while the posterior cingulate cortex helps us evaluate our internal states. The researchers told Huffington Post that changes to the former could help to explain why some women experience negative emotional side effects, such as anxiety and depression, when they commence the pill.
Although the study cannot prove whether oral contraceptives are causing these alterations in brain morphology, or if they are merely indirectly linked to them, the findings are interesting because they contradict an earlier study. Back in 2010, scientists documented that women taking hormonal contraceptives had numerous cortical regions that were larger than those in women not using contraceptives. Once again, some of these regions were involved in regulating emotions.
As Medical News Today points out, given that sex hormones, like estrogen, strongly influence the brain and nervous system, it does make sense that hormonal contraceptives could be exerting side effects on these parts of the body. That being said, it is unclear at this stage as to whether the alterations observed so far are permanent, or disappear when a woman goes off the pill. Furthermore, we don’t know if they are actually causing changes in behavior or cognition, which is why further studies are needed.