The concordance rate for schizophrenic disorder is higher for an individual if they have __________ who has been diagnosed with the disorder.

Concordance rate is the likelihood that both members of a pair have the disorder when one does. Identical twins share nearly all their genes, so schizophrenia concordance is higher for someone whose identical twin has been diagnosed than for someone with a fraternal twin, sibling, or one biological parent with the disorder.

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