For some women with epilepsy, the frequency or intensity of their seizures changes at certain times during their menstrual cycle – for example, around their period, or during ovulation.
This pattern of seizures aligned with a person’s menstrual cycle is known as catamenial epilepsy. Though they might be predictable, these uncontrolled seizures have a big impact on the lives of thousands of women and girls. It is thought to affect 4 in 10 women with epilepsy – though this figure is certainly an underestimate, as catamenial epilepsy is under-diagnosed.
We don’t fully understand exactly how catamenial epilepsy occurs. Research has suggested that, as levels of female sex hormones rise and fall during the menstrual cycle, they change the excitability of the neurons in the brain, increasing a person’s susceptibility to seizures.
Despite the impact it has on thousands of women and girls, catamenial epilepsy is under-studied in research, and overlooked in treatment plans. This is why catamenial epilepsy is a focus area for the Epilepsy Research Institute, as part of our Reproduction & Hormones theme.
While fluctuating hormones are the cause of catamenial epilepsy, they also point to an opportunity for treatment.
For example, the hormone progesterone rises during the second (luteal) phase of the cycle (see diagram above) and is believed to have anti-seizure activity. Taking additional progesterone during the luteal phase has been shown to reduce seizures for some women with catamenial epilepsy. However, the evidence around the effectiveness of hormonal therapies is not certain, as larger trials have failed to show a significant effect.
Hormonal treatments have downsides too. In the case of progesterone, women need to take a high dose several times a day to achieve the levels needed to have any effect. Certain types of hormonal therapy are also used as contraceptives, which might be desirable for some women, but for others would interfere with their plans to get pregnant. Hormone treatments can also carry side effects such as hot flushes, breast pain, vaginal dryness, and pain during sex. Long-term hormonal therapy can lead to issues such as osteoporosis and heart disease.
Hormonal therapies may hold part of the answer to treatment of catamenial epilepsy. However, more research is needed to gather good quality evidence of effectiveness and develop new options that minimise side effects.
Existing non-hormonal treatments for epilepsy could also be repurposed to improve seizure control in people with catamenial epilepsy.
For example, acetazolamide and benzodiazepines are usually used as ‘rescue’ therapies after a seizure, not for continuous usage to prevent them. But if taken for short periods at certain points of the menstrual cycle, they could have a seizure-controlling effect.
Further research is needed to explore the potential of re-using existing anti-seizure medications in a smarter way for treating catamenial epilepsy.
Catamenial epilepsy is not the first women’s health issue to be overlooked and under-researched. More research investment is well overdue.
The gaps in our knowledge of catamenial epilepsy were highlighted in our recent workshop on Reproduction & Hormones in May 2025. This workshop brought together experts and scientists to discuss the latest research into the effects of hormones and pregnancy on epilepsy. Crucially, people affected by epilepsy were also at the workshop and part of the discussions, which fostered collaborations that could lead to new research projects.
By giving catamenial epilepsy the attention and research funding it deserves, we will understand it better and find more effective treatments. This will help thousands of women and girls restore their control over their epilepsy, and one day help everyone to live seizure-free.
Find out more about the work we’re doing into Reproduction & Hormones – one of the Institute’s key themes for research.
