No one in my family has a history of bipolar disorder or depression... but I'm also missing 1/4 of my family history because my mom's dad abandoned her when she was 2 or 3. We don't know much about him, except that he left to fight in the Vietnam War, got a purple heart, then disappeared after that. But, my mom neither has depression nor BP.

Even those of you who have a family history of BP, you can trace your family tree back and you'll eventually find someone who doesn't have BP. At that point, you'll be able to identify the person who "started" BP in your family tree.

In my case, I'm probably the person who starts BP in my family tree. Someone has to start it.

I certainly think there is a genetic component, but BP isn't necessarily "inherited" (which is what I think you were getting at?). BP is probably a genetic mutation, and that genetic mutation can be passed down... but that genetic mutation can also happen to anyone during gestation.

So, no matter the way you interpret it, BP by very nature is "genetic" (i.e., it's not a disorder like PTSD which is caused by a traumatic event). There will always be a genetic component.

And yes, there are definitely environmental factors involved as well, but I think those environmental factors should be interpreted as "triggers". There are plenty of people who carry recessive genes for some pretty nasty diseases and disorders, but they never actually get those diseases/disorders because nothing triggers those genetic mutations.

If BP didn't have any environmental factors and it was 100% genetic, then we would show symptoms of BP at birth. It'd be something like Down's Syndrome. But, since BP can start at any age, there is obviously a trigger involved somewhere.

hope that answers your question