Millions of women taking hormonal contraception may be at higher risk of memory loss, concerning research has suggested.
Experts say women who take birth control like the Pill, implant or patch, tend to remember different aspects of an incident from those with natural menstrual cycles.
By changing a woman’s hormone balance, the drug alters the way she remembers unpleasant information.
According to US researchers, those taking the drug are less likely to remember details of a negative event, instead reinterpreting its events to protect emotional impact.
Scientists today, who labelled the findings ‘exciting’, said that remembering fewer details ‘may actually be protective’.
But they cautioned further research was first essential to prove if there was a link.
Beatriz Brandao, a cognitive neuroscience researcher at Rice University in Houston, Texas and study lead author, said: ‘For women, the findings highlight what many have long suspected—birth control can affect more than reproductive health.
‘It does more than prevent pregnancy—it also influences brain areas involved in emotions and memory, which are central to mental health.
Experts say women who take birth control like the Pill (pictured), implant or patch, tend to remember different aspects of an incident from those with natural menstrual cycles
‘We were surprised to find that when women on hormonal birth control used strategies like distancing or reinterpretation, they remembered fewer details of negative events.
‘That reduced memory for unpleasant experiences may actually be protective.’
Dr Stephanie Leal, an assistant professor of psychological sciences at Rice University and study co-author, added: ‘These findings are very exciting.
‘They suggest that hormonal birth control has the ability to modulate both how women can regulate their emotions as well as how that regulation may influence memory, especially toward negative experiences.’
Common forms of hormonal contraception include the combined oral contraceptive (pill) and progestogen-only pill (mini-pill), the contraceptive patch, the vaginal ring, the progesterone injection, the hormonal implant, and the hormonal intrauterine device (IUD).
Other than natural family planning, condoms, IUDs and diaphragms are among the few other non-hormonal options available to women.
In the study, researchers tracked 179 women, half of whom were on hormonal contraception and the other half, natural cycling.
Some 79 of the 87 women on contraception were taking the Pill.
The proportion of women taking oral contraceptives has fallen by more than two-thirds, from 420,600 in 2012/13 to 126,400 in 2022/23, according to the NHS data. Around 555,400 women turned to the health service’s sexual and reproductive health services in 2022/23 — equivalent to four per cent of 13 to 54-year-olds
Participants then completed questionnaires to assess how effectively they regulated their emotions, their habits and mental health.
They also viewed positive, negative and neutral images while applying different emotion regulation strategies, such as distancing, reinterpretation or immersion, and later completed a memory test.
Distancing involves mentally creating distance from an emotional trigger to gain a more objective perspective and reduce emotional intensity.
Immersion, meanwhile, involves people adopting an immersed perspective, immersing themselves in the image.
The researchers found women on hormonal contraceptives showed stronger emotional reactions compared to naturally cycling women.
When they used strategies like distancing or reinterpretation, they also remembered fewer details of negative events, though their general memory remained intact.
Writing in the journal Hormones and Behaviour, the scientists said: ‘Hormonal contraception use is associated with altered emotional reactivity, greater emotion regulation strategy effectiveness, and downstream effects on particular types of memory.’
The hormonal contraception findings were the same as for those who used the Pill, suggesting ‘these effects are evident when using the most common hormonal contraception formulation’, they added.
‘Our research encourages a comprehensive approach to women’s health care that integrates psychological and cognitive considerations into the prescription and management of hormonal contraception,’ the wrote.
However, the researchers also acknowledged the study had ‘some limitations’ including the fact most women on hormonal contraception were on the Pill.
The study also failed to track precise menstrual cycle phase data for naturally cycling participants, limiting researcher’s abilities to examine the role of hormonal fluctuations in emotion regulation and memory performance.
The scientists now plan to assess the impact of this by tracking naturally cycling women across different menstrual phases and comparing types of hormonal contraceptives, such as pills versus IUDs.
‘Ultimately, our goal is to understand how reproductive hormones—whether natural or synthetic—shape emotional health so that women can make more informed choices about their reproductive and mental health,’ Ms Brandao said.
Previous research has shown a link between hormonal contraception and altered brain function in areas responsible for motivation, emotion and attention.
Additionally, oestrogen levels, which are generally lower for hormonal contraception users, are found to play a key role in hippocampal function, also involved in emotion control as well as motivation.
Known side effects of the Pill—proven to be over 99 per cent effective at stopping pregnancy and the most popular form of contraception—include nausea, breast tenderness, mood swings and headaches.
Others claim they pile on pounds while taking the because of increased fluid retention and appetite, yet the NHS says there is no evidence it leads to weight gain.
Decades of research has failed to provide any conclusive evidence that this supposed side effect is real.
However, rarer side effects include blood clots and a slightly heightened risk of breast and cervical cancer.
Approximately three million women in the UK take the contraceptive pill, and a further 11million women in the US use hormonal contraceptives.
