Receiving a prescription for the oral contraceptive pill is practically a rite of passage for Australian women, with up to 80% using ‘the Pill’ at some stage in their reproductive lives.
Aside from prevention of unwanted pregnancy, oral contraceptives are prescribed to control acne, excessive facial hair, painful periods and heavy menstrual bleeding, as well as to supposedly ‘regulate’ the menstrual cycle of women with polycystic ovarian syndrome (PCOS).
Although the Pill is touted as a safe and effective method of contraception, recent studies have revealed that it has significant effects on the structure and function of women’s brains – especially those who begin using it during adolescence, when the brain is still undergoing significant development.
As I have discussed in previous articles, use of the oral contraceptive pill is linked to an increased risk of depression, especially when commenced in adolescence.
Two recently published studies have increased our understanding of the mechanisms by which the Pill affects women’s brains and behaviour.
In a study titled Use of the birth control pill affects stress reactivity and brain structure and function, researchers used functional magnetic resonance imaging (fMRI) to study the brain activity of both users and non-users of the Pill whilst they were viewing images that were either emotionally neutral (e.g. shoes, drawers), positive (e.g. cute puppies, beautiful sunsets) or negative (e.g. car accidents, guns).
Participants’ reactivity to cognitively and socially stressful stimuli was also measured.
Women who were taking oral contraceptives were observed to have increased activation in the prefrontal cortex of their brains while viewing emotionally negative images, which has been linked in previous research to a fear response.
Those who had begun taking using oral contraceptives during their teenage years showed a blunted response to a social stressor. This blunted stress reactivity has previously been found to be a risk factor for depression.
Furthermore, the MRI images revealed differences in brain structure between Pill users and non-users., which the researchers speculated
“may be due to a delay or suppression of the natural synaptic pruning process that occurs in early adulthood,”
pointing out that previous research has identified associations between these specific changes and
“aspects of cognitive decline and depressive symptom severity.”
A neuroimaging study presented at the 2019 annual meeting of the Radiological Society of North America found that women taking the oral contraceptive pill have significantly smaller volume of the hypothalamus, a region of the brain that produces many hormones and helps regulate essential bodily functions including body temperature, mood, appetite, sex drive, sleep cycles and heart rate.
The lead author of the study commented that the difference in hypothalamic volume between Pill users and non-users was “dramatic”, and also pointed out that smaller hypothalamic volume had been strong correlated associated in previous studies with depressive symptoms, and was also linked with greater anger.
The two recent studies contribute to a small but rapidly growing body of research that suggests that oral contraceptives are far from the benign passport to freedom from unwanted pregnancy that they have been presented as, since the first Pill reached the market in the early 1960s.
While more research is needed before firm conclusions can be drawn, these studies should give doctors serious pause for thought before prescribing oral contraceptives, especially to teenage girls whose brains are undergoing rapid development.
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