Sunday Longread: The power of the pill

Your brain on hormonal contraceptives

Approximately 73% of women ages 17-45 have used the combined oral contraceptive pill at some point in their lives, according to research conducted by the Dublin Well Women Centre in 2020. Given such popular use, and the recent news that the combined pill alongside other contraception options will become freely available in Ireland to those aged 17-24 from mid next year, it is time we spoke more openly about the so-called ‘pill’ and its lesser-known effects on behaviour.

“Other psychological and behavioural side effects (not necessarily negative ones), gain little attention compared to the established physical ones.”

The combined oral contraceptive pill contains a combination of two synthetic versions of the female hormones oestrogen and progesterone, which are responsible for regulating a menstrual cycle. However, these hormones also have other secondary functions in the body, explaining the numerous potential side effects of hormonal contraceptives. However, aside from its ability to prevent pregnancy, the combined pill is also taken by many to manage symptoms of conditions such as endometriosis and hormonal acne and therefore, for most, the benefits certainly outweigh any risks. The association of weight change, nausea, headaches and other physical side effects with oral contraceptives is both well documented in research and well-known by pill takers. However, other psychological and behavioural side effects (not necessarily negative ones), gain little attention compared to the established physical ones and like many women’s health issues, are heavily under-researched.

Surprisingly, oral contraceptive pills have been shown to affect mate choice. This occurs because, in a normal menstrual cycle, there are predictable hormonal fluctuations that lead to changes in partner preference. Women at ovulation (a point of high oestrogen levels), when they’re most fertile, tend to prefer more masculine features and partners who are genetically dissimilar. This has the clear evolutionary advantage of their offspring having greater genetic diversity, which translates to a stronger immune system among other advantages. However, given the steady hormone levels in contraceptive pill users, which mimic those seen in pregnancy, these ovulation-specific preferences do not occur. Instead, women who take the pill do not exhibit this preference for someone more genetically dissimilar and this loss may possibly translate to increased fertility problems globally.

“The recall of ‘negative stimuli’ was diminished in oral contraceptive users in comparison to positive stimuli.”

Hormonal contraceptives have also been shown to be capable of altering emotional memory, however not in a negative sense. Studies have shown that contraceptive pill users typically have elevated cortisol levels. Cortisol is a primary stress hormone, responsible for that ‘fight or flight’ sensation and is central in memory formation and recall. These studies have also noted that these high baseline levels lead to a blunted cortisol response to stress, in comparison to natural-cycling women. Although interestingly, the recall of ‘negative stimuli’ (a way of mimicking negative memories in an experimental setting) was diminished in oral contraceptive users in comparison to positive stimuli, meaning more positive emotional memories were recalled better than negative ones. On the contrary, those experiencing depression, who also have a higher baseline of cortisol levels, tend to have a bias for negative stimuli, meaning they are better at recalling negative memories. A study conducted by Mordecai et al. in 2017, stated how further investigation into the possible protective role that oral contraceptives may offer against this preferential recall is of great importance.

Despite this possible protecting effect that oral contraceptives may play for those affected by depression, the pill has been associated with depressive symptoms, with discussions in literature as early as the 1960s. However, there have been many contradictory findings in studies conducted since then, with the existence of a link still open for discussion. While most combined pills list depression as an uncommon side effect (affecting up to 1 in 100), side effects such as “emotional lability” or “mood swings” are generally listed as common (up to 1 in 10).  These potential side effects occur as oestrogen and progesterone (the pill contains synthetic versions of each) share common pathways and receptor sites in parts of the brain responsible for mood modulation and emotional control. Therefore, despite their lengthy existence, further research is still needed to definitively determine the possibility of the pill causing negative effects on mood, and especially which groups this may be most applicable to, for example, those who have a history of depression.

Overall, the combined oral contraceptive pill has been a primary method of birth control for millions of women since the 1960s and are highly efficient, rendering the side effects mentioned above rather insignificant. However, numerous studies highlight that the psychological effects of this method of birth control are under-researched despite such extensive use globally, as will many aspects of women’s health. However further investigation may be hugely beneficial not only to women using the pill but also to better understand the reproductive system and as seen above, even conditions such as mood disorders.


Sophie Maguire

Sophie Maguire is a Staff Writer for Trinity News.