I think they usually _don’t_ use twin studies because they are harder/more expen...

		sambe on June 1, 2019 \| parent \| context \| favorite \| on: Childhood Adversity Linked to Earlier Puberty, Pre... I think they usually _don’t_ use twin studies because they are harder/more expensive. In this case they used the Philadelphia Neurodevelopmental Cohort: https://www.med.upenn.edu/bbl/philadelphianeurodevelopmental... I don’t see any mention of twins here or on JAMA, although I can’t access the full text currently.