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Thought Leadership

Your brain on hormonal contraception: what does it mean for you?

By Onyx Health | 28th February 2023

Read Time: 4 minutes


If you’ve spent any portion of the past 60 years trying to protect against pregnancy, chances are you’ll be familiar with hormonal contraception in some form. The birth control pill, intrauterine device, and hormonal injections are among methods that millions across the world rely on every day to prevent becoming pregnant, as well as to manage acne and various gynaecological conditions. 

Despite the widespread availability of hormonal contraception for over half a century, relatively little is known about its effects on our brains. But more recent studies using magnetic resonance imaging (MRI) show differences in the brain structures of oral contraceptive pill-takers, compared to naturally-cycling women.

So, what could this mean for our brains, and in turn, our stress response, quality of sleep, learning and memory?

A bad lock or a wonky key? Hormonal contraceptives and their attempt to mimic natural hormones

Birth control pills function primarily to prevent pregnancies. The progesterone component of birth control pills elevates progesterone levels and suppresses the secretion of gonadotropin-releasing hormone and follicle-stimulating hormone, thereby tricking the body into thinking it’s pregnant so that an egg isn’t released when it naturally otherwise would be. What that also means, however, is that oestradiol (an oestrogen steroid hormone) levels in those taking the pill are low.

Women with high levels of oestradiol may look and feel prettier (in accordance with unfounded societal norms), and be more inclined to demonstrate thrill-seeking behaviour attributed to opportunistic mating. While most (combined) oral contraceptive pills contain some levels of oestrogen to combat and offset adverse events that occur with progesterone and cardiovascular risks associated with oestradiol, the low oestradiol levels of around 20-80 pg per millimetre may be around 4x less than premenopausal ranges.

What’s more, progestins, the synthetic progesterone that make up contraceptive pills, are just that. Synthetic. This means that the structure of these laboratory-generated compounds is modified and so they do not accurately mimic the natural parent molecules of progesterone or testosterone. So, because progestins don’t completely match the structure of progesterone, they may stimulate other receptors, such as androgen, oestrogen, and glucocorticoid receptors (and potentially cortisol), which may accentuate the stress response.

Hormonal contraception and your stress response: the curious case of the missing cortisol

Though mood swings have long been recognised as a prominent side effect of the contraceptive pill, it was only recently that research identifying exactly how these little pills affect the brain (despite women making up half of the world’s population) has picked up. What we have known for a while, however, is that the contraceptive pill has some effect on cortisol levels.

Cortisol is known as the human body’s stress hormone . When we are under real or perceived threat, cortisol is released to prime the body for a ‘fight-or-flight’ situation. While part of cortisol’s task is to suppress functions of the human body that would be nonessential or counterproductive in such a situation, its role has rather more nuanced implications for the regions of the brain that control mood, fear and motivation. 

Its effects are far reaching: cortisol alters our brain, bloodstream and immune system, and depresses our growth process, and digestive and reproductive systems. Women taking hormonal contraception have been found to have higher cortisol levels compared to women who aren’t, meaning that they have a dysregulated response to stress. In fact, research suggests that pill-taking women experience stress in a similar way to those who struggle from chronic mental stress; and this can have profound effects on mental health. 

The mental toll of avoiding pregnancy 

Someone who takes the contraceptive pill may struggle with mental health conditions such as depression, anxiety, and suicidal behaviour from time to time. You may also hear that some people with severe cyclical changes find that oral contraceptives help improve their mood, but then again, everyone is different. Attention must be paid to the ~ 43% of pill taking women who avoid pregnancy with a cost to their mental health and well-being. 

The mechanism underlying just how these little pills drastically affect moods remains controversial, with recent review articles demonstrating significant limitations due to the lack of structured categorisation of study participants, lack of methods to define mood changes, and the reduced interest for future studies surrounding the topic. The mood changes associated with oral contraceptive use have previously been linked to biochemical processes that alter serotonin (the happy neurotransmitter) levels.  

It is also proposed that negative mood may reflect the effects of the pill on the brain’s reward system. Biologically produced oestradiol and progesterone have some effect on the reward system. Though studies of the impacts of hormonal contraceptives on this mechanism are sparse, one study reported those taking the pill have lower cortical thickness than naturally cycling women. As the frontal cortex plays a vital role in regulating behaviour, it can be deduced that women taking the pill show a blunted response to reward, though further studies are needed to support these findings. 

Memory… foam?

It’s hard enough having to remember to take the pill at the same time EVERY SINGLE DAY (unless you’re on a 21-day schedule), never mind having to battle against the potential affects the pill has on memory and sleep.

There are many reasons why we can expect the pill to affect memory as the pill’s constituents are synthetic variants of natural hormones that do influence the brain and behaviour. 

Research suggests that taking the pill can also cause structural changes in the brain regions that control memory and emotion, which can also explain why mental illness is common in women taking the pill.

But that’s not all. In addition to debilitating mental health issues and the potential to affect memory, there’s also a connection between taking the pill and poor quality sleep. Mental health conditions caused by the pill, such as depression, can contribute to sleep disturbances. It is argued that though oestrogen and progesterone have a hypnotic effect which increases sleep quality, these hormones can alter your body temperature which can interfere with sleep. There may well be other mechanisms by which the pill can cause poor sleep, such as affecting the circadian rhythm, but conclusive evidence lacks.

3 ways to avoid a pregnancy: a dash of insomnia, a sprinkle of depression, and…

Although women are frequently concerned with the side effects of the contraceptive pill, it seems that little has been done to research why these side effects occur, despite data suggesting the possibility of several brain alterations attributed to contraceptive pill use. Admittedly, more evidence is required to attribute these findings to a larger cohort, half-a-century-old concerns surrounding the pill and its side effects remain unaddressed, prompting us to ask why we really need to think about the pill and why, in a an era full of rapid medical discovery, no one has invented a better solution for everyone. 

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