Question: Can a head injury or complications during birth cause bipolar disorder?
Answer: There have been some studies that have found a higher incidence of obstetrical complications in adults who have bipolar disorder. In other words, when they were babies, there were some complications around their birth and during the pregnancy of their mother.
But it's not clear exactly how these complications or difficulties lead to bipolar disorder. And it's also not clear that head trauma or head injury early on definitively leads to bipolar disorder, but it can, just like it can lead to a whole host of other kinds of neurological or psychiatric disorders.
However, the biggest risk factor does appear to be genetics, and so again if there is a family history of bipolar disorder, perhaps combined with things like obstetrical complications or head injury, those two things could possibly worsen the outcome so that you are more likely to develop bipolar disorder.