But it is, because we're talking about persistent deficiency of certain neurotransmitters in the brain, that's most likely[0] due to different brain makeup. You can't do enough PE to mitigate this and have enough energy left for everything else.

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[0] - I say "most likely" because I didn't investigate the claims that MRI can pick up on the difference. But from my initial difference, the effect is still hereditary, in at least large part genetic.