How do you expect this to work: To get a gender imblance, only one of the sexes would have to suffer these adverse effects due to, say, nutrition. That would likely still be caused by social factors...
Because makes and females have different nutrition, different habits and fir example use different drugs. It may be something silly like different contents of birth control pills. It's not a secret that small changes in amount of consumed zink, calcium or iodine make big impact on body and mental abilities.