These are twin studies, you don't need to get into heritable epigenitics. The expression of the shared environment in the womb would be reasonably expected to lead to epigenetic correlations in twins at a crucial stage of development where they would have the highest impact, without them being heritable.

Put simply, the common epigenetics between twins need not be held in common with the parents.

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Aurornis 3 hours ago | parent [-]

> The expression of the shared environment in the womb would be reasonably expected to lead to epigenetic correlations in twins at a crucial stage of development where they would have the highest impact, without them being heritable.

Sure, but that wouldn't be relevant to twin studies because both twins would be exposed to the same environment.

The pop culture discussion about heritable epigenetics tends to assume influence outside of in utero conditions or crossing multiple generations. It's where the "generational trauma is in your genes" idea came from.

	▲	tptacek 3 hours ago \| parent \| next [-]
		We're discussing twins raised apart. They're not necessarily in the same environment (except during gestation).
	▲	sudosysgen 3 hours ago \| parent \| prev [-]
		It would be relevant to twin studies. Specifically, separated twin studies, where shared environment is assumed to be negligible. If the developmental impact of epigenetics is significant that won't be true.