Andrew Huberman· PhD
If estrogen levels are increased experimentally under long day conditions, it does not evoke aggression. However, in short days, if estrogen is increased, there's a heightened predisposition for aggression.
The evidence is convergent. Multiple independent sources reach the same conclusion, the underlying mechanism is well-characterized, and even the field's most cautious voices treat it as worth doing.
If estrogen levels are increased experimentally under long day conditions, it does not evoke aggression. However, in short days, if estrogen is increased, there's a heightened predisposition for aggression.
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Photo period reverses the effects of estrogens on male aggression, via genomic and non-genomic pathways.
Whether or not that person with the particular gene variant is more aggressive or not, depends on how long the day is and how long the night is.
There are beautiful data showing that whether or not estrogen stimulates aggression, can be powerfully modulated by whether or not days are short or days are long.
there is a genetic variant present in certain people that adjusts their estrogen receptor sensitivity, and that estrogen receptor sensitivity can result in increased levels of aggression, sometimes dramatic increases, however, and also very interestingly, photo period, meaning day length, is a strong modulator of whether or not that aggressiveness turns up or not.