Ms. Dr. Heller, you spent a total of more than three days and nights in an MRI scanner (MRI). Do you have a special relationship with this device?
At least I now know exactly how test subjects, i.e. test subjects in scientific studies, feel. At first I was a little nervous and had to get used to the tightness. But at some point the examination became routine and I was able to relax. Which was good, because you have to lie very still. I am grateful for the experience because it made me a better scientist. After the last of the 75 measurements I was a little sad that it was over.
They examined your brain to find out more about how sex hormones affect the central nervous system. How did you come up with the idea of making yourself your own test subject?
I was inspired by two colleagues: the neuroscientist Dr. Emily Jacobs from the University of California at Santa Barbara and her then doctoral student Dr. Laura Pritschet. She was also her own test subject when the two wanted to find out
Instead, they wanted to research how the pill changes the brain. Why?
I had been on the pill for over twelve years and stopped taking it about five years before I started trying. I still remembered that I noticed more mood swings after I stopped taking it. There have been smaller studies that have shown that subjects who took the pill had, on average, less gray matter. My boss at the Friedrich Schiller University Jena, Prof. Ilona Croy, and my boss at the University Hospital Jena, Prof. Martin Walter, supported my idea. And luckily I was able to meet my colleague in medical physics, Dr. Daniel Güllmar, enthusiastic about my project. He operated the MRI machine while I lay in it.
To person
Dr. Carina Heller is a psychologist and received her doctorate from the Friedrich Schiller University in Jena. During her doctoral work, she worked with the Psychiatry Neuroimaging Laboratory (PNL), Harvard Medical School and the Brigham and Women’s Hospital in Boston, USA. After completing her doctorate, she began working as a research assistant, which gave her the idea of self-experimentation in 2022. The scientist is now 32 and has been conducting research at the University of Minnesota Twin Cities and the University of California in Santa Barbara since September 2024.
How long have we known that the brain responds to sex hormones?
It has been clear since the 1920s that estrogen and progesterone influence the brain. In the 1960s, specific receptors for these hormones were found in the brain, including in men.
Estrogen and progesterone are the female sex hormones…
… men’s bodies also produce it, in smaller quantities. Estrogen and progesterone play important roles in brain development in all genders. How exactly they influence brain function has not been fully researched. Among other things, because most biomedical research used to focus on men. Until the 1990s, women were excluded from clinical trials.
As early as 1960, a drug for women came onto the market in the USA that changed the world: the birth control pill, which was approved for contraception in Germany a year later.
That was more than 60 years ago, and yet we know very little about how the pill and its hormones affect the brain. That’s frightening. Research into this only emerged about 20 years ago.
What came of it?
That estrogen and progesterone have profound effects on the brain. Estrogen supports synapse formation, which is important for memory and learning processes. Progesterone is thought to protect nerve cells. If hormone levels fluctuate, for example during the cycle, this becomes noticeable in the brain.
To what extent?
The so-called functional connectivity, the interaction between brain regions, changes. Estrogen improves this connectivity and allows the brain to work more efficiently. In addition, the volume fluctuates with hormones.
Do you mean the brain shrinks or grows?
I wouldn’t put it that way – we don’t even know what that means yet. But my previously mentioned colleagues Emily Jacobs and Laura Pritschet found that during pregnancy, when the levels of estrogen and progesterone increase dramatically, they are essentially the coat of the brain in which the nerve endings are located.
Is the brain less efficient when this mantle is smaller?
No, volume reduction doesn’t have to be a bad thing – Jacobs interpreted the changes more as a profound reorganization of the brain. Reorganization of nerve cells also occurs during other hormonal transition periods, such as during puberty or menopause. The fact that the risk of mental illness is greater in such phases could be related to this.
Why did you only carry out the experiments on yourself – don’t serious studies require a large number of test subjects?
Even financing would have been difficult: an MRI hour costs around 300 euros. I would also have needed absolutely reliable test subjects: They would have had to come to the clinic 75 times at 7:30 a.m. for one or two hours. I knew that I would be my best test person: reliable and motivated to complete this study – even though I’m really not an early riser.
Is an experiment with just one test subject even a study?
Of course, I am not a representative sample. However, it is not uncommon to test something yourself in order to obtain clues. From an individual history that is examined in great detail, hypotheses for larger studies can certainly be generated. Because the fact is: So far, no one has examined the influence of the cycle and the pill in this way.
They looked at your brain during a normal cycle, then under Germany’s best-selling pill and a third time after stopping that pill – 25 times each, three times every morning for five weeks. In order to examine volume and brain activity, three different MRI procedures were necessary.
Exactly, that’s why the individual examinations took so long. I was in the tube for an hour on each of those 75 days, so 75 hours in total.
Weren’t those hours in the MRI terribly exhausting?
I never once thought about giving up. What I found more stressful was the blood tests that were necessary at every appointment to determine my hormone status. I also filled out a questionnaire with 20 questions about my current mood 75 times.
What did the questionnaire, blood tests and MRI images show?
My results have not yet been published and we are working on the evaluation. I can therefore only refer to preliminary results that I have already presented at a neuroscience conference in Chicago. During the natural menstrual cycle without hormonal contraception, the brain shows changes that affect the volume and connectivity between brain areas, which other studies suggest could affect thinking, emotions and well-being. The volume fluctuates by about one percent.
And while taking the pill?
There are also fluctuations in volume and connectivity – with the volume over the entire time being around one percent lower than without the pill. But don’t forget: less volume doesn’t have to be a negative thing. It can also mean that the brain works more efficiently. Conversely, better connectivity does not have to be an advantage.
So it’s still unclear what the pill does in the brain and what that means for women’s everyday lives?
Exactly, now it’s time to shed light on the darkness. Also, when it comes to different pills – my results only apply to the composition and dosage of the pill I took.
What can we still learn from your data?
It is important to further investigate these effects in order to be able to provide better personalized recommendations in the future. I don’t want to engage in pill bashing with my research; The pill is an extremely safe and well-tested drug with immense benefits that has given women a lot of freedom. Personally, I have had good experiences with this for twelve years.
Even when weaning?
The MRI data showed that brain volume and activity returned to natural cycle levels three months after discontinuation. Isn’t it fascinating how adaptable the brain is? Some women feel as if a veil has been lifted after discontinuation – that wasn’t the case for me. If you feel this way, the pill is probably not the right contraceptive method. But if you have extreme mood swings or premenstrual symptoms, the pill can bring stability to your cycle. For many it is therefore exactly right, for others it is not. Every woman should listen to her body and make this very personal decision depending on the phase of her life.
What about psychological side effects of the pill, i.e. depressive moods, mood swings and sexual loss?
There is no clear evidence that taking the pill is linked to mental illness. Nevertheless, I think it is important to take psychological problems seriously while taking the pill and to discuss them with a doctor.
Young people often take the pill. Is their brain even fully developed?
The brain develops from back to front, with hormones playing an important role. We assume that the frontal lobe in the forehead area is not fully mature until the age of 24. Whether the pill influences this has not been sufficiently scientifically investigated. However, in some studies it has been linked to an increased risk of depression in adolescents. Even for very young women, the decision for or against taking it should be well-informed and made individually.
How do you want to continue your research now?
First, we will thoroughly evaluate my data set. We then want to make it available to other scientists around the world. The next step is to increase the number of test subjects to see how representative my data is. I would also like to examine a test subject with endometriosis in an MRI. Estrogen is very dominant in the disease. It would be super interesting to see whether the changes in the brain are stronger.
Given your results, would you take the pill again?
I’m not taking it right now, but I’ve been thinking about starting again. If so, I would definitely do another study on it.
Source: Stern
I’m Caroline, a journalist and author for 24 Hours Worlds. I specialize in health-related news and stories, bringing real-world impact to readers across the globe. With my experience in journalism and writing in both print and online formats, I strive to provide reliable information that resonates with audiences from all walks of life.
