Original sentence: According to the "Kindling theory", periods of depression, mania, or "mixed" states of manic (euphoric) and depressive symptoms typically recur and may become more frequent, often disrupting work, school, family, and social life.Bipolar disorder may be caused by a combination of biological and psychological factors
Edited sentence: According to the "Kindling theory" and possibly assumed, periods of depression, mania, or "mixed" states of manic (euphoric) and depressive symptoms typically recur and may become more frequent, often disrupting work, school, family, and social life.As far as we are aware, the Kindling Theory has not been disputed.People can also be "prone" to bipolar disorder after substance abuse, or because of a neurological condition or brain damage.Scientists assert that recurring (as opposed to singular non-recurring) bipolar disorder may be caused by a combination of biological and psychological factors.The person then "becomes bipolar".This might explain why the cause of bipolar disorder is difficult to pinpoint but is somehow related to genetic and/or genetic and enviromental causes