[JohnHarlin]

If you have a large family of say 8 people and one person gets schizophrenia, how likely is it that a second or more member of the family will get schizophrenia?

[kaliope]

I think if I remember my statistics correctly, 1 in 8 people suffer from mental illness; however in my immediate family, my grandmother had bipolar, it skipped her two kids, and then my dad had six kids and myself and my two sisters have all been diagnosed bipolar and we suspect my brother is as well, so you never know.

[Sometimes psychotic]

Depends on who it is relative to you ...If it's a parent and we're talking kids...13%, if it's a brother or sister 9%, twin...28% general population risk is 1%. Importantly this is just for sz....in some families there is also an increase in bipolar or MDD which can also have psychotic components...

Honestly I don't remember enough about stats to calculate this specifically for an 8 person family but that's only 6 kids and to get to decent odds you'd need ten kids to get a second but it still happens....

I think importantly having sz in the family increases rather than decreases the probability of a second offspring having it....