The causes of bipolar disorders type I, and II can also vary. The average age for the commencement of bipolar type I disorder is 18, and for bipolar type II is in the mid-20s. As personal development differs from person to person, it is still not easy to describe what "normal" is for one age and another.Environmental causes - As stated by DSM-5, the percentage of people in advanced countries with bipolar disorder is twice as compared to underdeveloped countries. A higher number of people that are widowed, divorced, or separated can have bipolar disorder as compared to those who are or have never been married at present. There exist connections to marital status, even though its nature is not precise.Genetic and physiological causes - If someone in your family has bipolar disorder, you're around ten times more likely to have bipolar type I or II. If that family member is closer, you have a better chance of experiencing manic depression. There is also some proof that it relates to schizophrenia.