Does the Pill make brains bigger?

Behind the Headlines

Wednesday August 18 2010

The study is too small to prove that the Pill had a major effect

"Contraceptive pills increase the size of certain parts of women’s brains, improving memory and social skills", reported The Daily Telegraph.

This news story is based on a small study that looked at brain structure in 14 men and 28 women, half of whom were using hormonal contraception. It found that certain areas of grey matter in the brain were larger in women taking hormonal contraceptives than in women not using hormones, and in women in their early phase of their menstrual cycle compared to later in the cycle. The researchers say that this shows that both these factors can affect the human brain structure.

However, this study is too small to conclude that the Pill or the menstrual cycle affects the volume of grey matter in the brain. There is no way of knowing what other factors, including genetic factors, may have had an effect on these participants’ brains as no other data was taken. Also, since it did not actually examine or measure cognitive performance, it cannot shed any light on how the Pill might affect cognitive or social skills.

 

Where did the story come from?

The study was carried out by researchers from the Paris Lodron University of Salzburg and Paracelsus Private Medical University of Salzburg. It was funded by the Austrian Academy of Science. The research was published in the peer-reviewed journal Brain Research.

The Mail’s report, which included claims that the Pill “enhances the brain’s conversation hub”, exaggerated the significance of the study. There is no basis in the study for the newspaper’s claim that the Pill makes women brainier, nor for a similar report in the Telegraph that it improves memory and social skills.

 

What kind of research was this?

The researchers say that differences between the brain structure of men and women have been investigated many times. These studies have suggested that the amount of grey matter in particular parts of the brain differs between the sexes, but so far these differences have been inconsistent between studies. The researchers suggest that these inconsistencies may be due to hormonal fluctuations during the menstrual cycle or women’s use of hormonal contraceptives. They point out that most previous studies have not taken into account the effect of hormones.

This experimental study investigated possible differences in human brain structure between men and women at different phases of the menstrual cycle, and women using the contraceptive pill. They did this by measuring the volume of grey matter in their brains using an MRI scan. No direct measurements of cognitive abilities such as memory, navigation or social skills were taken.

 

What did the research involve?

The scientists used an MRI scanner to take high-resolution images of the brain structures of 14 healthy men and 28 healthy women, all in their early to mid-twenties. Half of the women were using the Pill, although the type, brand and dose was not recorded. Women who were not using the Pill were scanned twice, once during the early follicular part of the menstrual cycle, and once during the middle (or mid-luteal) phase.
 
All participants were not taking any other medications and had no history of any disorders that might affect brain structure or function. The women not using hormonal contraception had regular menstrual cycles and had not been diagnosed with any menstrual disorders.

Using the scans, the types of brain tissue were classified and the volume of various regions were measured. An analysis that compared the results between the three different groups was carried out.

 

What were the basic results?

The results were analysed according to gender, phase of cycle and use of hormonal contraception. Overall, men and women had differences in the volume of grey matter in different parts of the brain. In regions where women had larger volumes than men, this difference in size was more pronounced during the early part of the menstrual cycle (in naturally cycling women) and in women using hormonal contraception.

Gender-dependent effects

  • Men had a larger volume of grey matter in certain parts of the brain than both groups of women, especially compared to “naturally cycling” women in the phase when hormone levels are low.
  • Both groups of women had larger volumes in other regions of the brain, with the effect being most pronounced in hormonal contraceptive users.
  • The grey matter volume in the cerebellum (the region just above the brain stem that has an important role in motor control), was larger in men than naturally cycling women, but larger in women on hormonal contraception than in men.

Cycle-dependent effects

  • Naturally cycling women had significantly more grey matter in certain regions during the early phase of the cycle than in the later phase.

Effects of hormonal contraceptives

  • Women using hormonal contraception showed more grey matter in certain regions of the brain than naturally cycling women during both cycle phases.

 

How did the researchers interpret the results?

The researchers conclude that sex hormones have a “tremendous effect” on brain structure, as demonstrated by differences between hormonal contraceptive users and naturally cycling women in the amount of grey matter in certain regions. In regions that were already larger in women compared to men, using hormones was associated with an even larger volume of grey matter. In men, the regions with more grey matter were hardly affected by contraceptive use.

The researchers say this finding could be related to earlier suggestions that the menstrual cycle affects performance variations in memory and sex differences in “navigation abilities”.

 

Conclusion

This small study seems to show that in certain regions of the brain, women using hormonal contraception had larger GM volume than naturally cycling women. The researchers suggest that this may be due to differences in hormone levels, specifically “enhanced” oestrogen and/or progesterone levels. They conclude that more clarification is needed on the specific roles of oestrogen and progesterone.

While this small study is interesting, it is too small to draw any conclusions about the differences in brain structure between men and women, and between women taking the Pill and those who are not. It did not take into account any other factor that might affect brain structure (other than ensuring the absence of disease in participants). In the naturally cycling group, it also relies on women self-reporting the stages of their cycle, which introduces the possibility of error.

It is important to emphasise that the study did not measure the participants’ cognitive function, so no conclusions can be drawn from this study about the effects of hormonal contraception on cognitive abilities or skills.







Analysis by Bazian

Edited by NHS Choices

Links to the headlines

The Pill makes you brainier: It can swell grey matter essential for social skills and memory, say scientists. Daily Mail, August 18 2010

Contraceptive pill 'increases brain size and function'. The Daily Telegraph, August 18 2010

Links to the science

Pletzer B, Kronbichler M, Aichhorn M et alMenstrual cycle and hormonal contraceptive use modulate human brain structure. Brain Research 2010: 1348; 55-62

Further reading


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