I always thought it was a joke when my friend said in high school ; My birth-control pills are making me stupid!
I thought she was just being incredibly silly, and more than once, I have heard male friends say that their girlfriends have become more forgetful, not noticeably but that certain cognitive skills seemed to decrease. I would get pissed, why does everyone blame it on oestrogen! Its like slapping females on the face, but picking up the paper, I see article “Excess of oestrogen decreases cortical matter”, so I look it up and there it is. Oestrogen, when lost can make you preform cognitive task less efficiently (http://jama.ama-assn.org/cgi/content/abstract/281/13/1197 )
And when you have it in a larger amount, makes your cognition and brain matter (particularly in the hippocampal area) decrease! Weather or not it applies to birth-control pills, I do not know. Probably not, I have to go the source.
So, I guess my friend was a bit on the way to the truth, and those guys weren’t perhaps being mean to their girlfriends. Such a sad fact to find out, explains a lot however. The same seemed to apply with men and testosterone, I guess we can be “slow” together (laughter).
However, it was not irreversible nor sufficient to make you “stupid” so sorry friend, you were not stupid, you were just probably unmotivated to study that day.
Reference will come later, since the study was from a popular culture magazine, it will take some time to track down the original in the dungeons of PubMed.
Here is something related in the meanwhile; http://jnnp.bmj.com/cgi/content/full/74/7/837