Posted by Larry Hoover on November 7, 2005, at 8:12:24
In reply to Family History Sibling or Parents?more significant, posted by ADDFazed on November 6, 2005, at 13:58:44
> Which is more significant in family history for diagnosing what mental illness you have? -
> Siblings or your parents?
>
> I say my siblings
> because it's farther down the family tree.From a genetic standpoint, you share 50% of each of your parent's genes. Your siblings have a 50% chance of getting the same 50% of each parent that you did, so they share 25% of your genes. ON AVERAGE. By chance, these sibling numbers could be a little higher or a little lower.
> If you have -say- a 50% chance of having ADD from
> one side and 30% chance from the other parent
> your chances go up exponentially right?A 50% chance of a disease from one parent and a 30% chance of it from the other, if both must be positive for the disease to manifest (double recessive), the odds are 3 in 20 (1/2 times 3/10), or 7.5% that you will get the disease. If it is a fully dominant disorder, the odds are 1/2 + 3/10 = 80%. In reality, few diseases are fully dominant, and require one single gene for expression, so the odds are more likely to be in the vicinity of the average of your parents' risk, or about 40%.
That's the genetic predisposition. However, you share a common environment with your siblings. Genes react to the environment. Your parents came from different wombs than you did (or each other), and were exposed to entirely different and distinct environments until they reached adulthood. Siblings share very similar environments, and that often includes things like diseases (you all get the same bug that's going around), and environmental toxins.
However, your question was about diagnosis. You and your siblings are more likely to be diagnosed under similar diagnostic descriptions, at around the same time. That would make it more likely that you would be diagnosed using the same terminology. Your mom's neurosis might be today's GAD, so it's awfully hard to know how to interpret historical diagnoses fairly.
Lar
poster:Larry Hoover
thread:576012
URL: http://www.dr-bob.org/babble/20051106/msgs/576291.html