A family history of mood disorders is the only well-documented risk factor. That said, there is a growing interest in the possibility of environmental factors, such as stress and drugs, triggering or activating bipolar disorder, especially in individuals who may have a genetic susceptibility or vulnerability.
At present, with no tests that can positively determine who will and who won’t develop bipolar, even in families with a history of it, the best we can say is that the risk increases, or decreases, depending on how many family members have mood disorders and how closely related they are to you.
From a practical perspective, if you think you are at greater risk for developing bipolar, it makes sense to avoid exposure to drugs, alcohol, and undue stress. While not studied, strategies discussed throughout this book, such as establishing and sticking to regular routines, maintaining healthy sleep/wake cycles, etc., might well be effective in helping a person with a genetic susceptibility from going on to develop bipolar.