I cannot find this blog now. I have once happened upon a blog maintained by a guy whose wife has BP. He posited that BP is essentially a sleep disorder. I am so dependent on the quality of sleep I get that I am ready to agree with him. Sleep can be both a trigger - you spend a sleepless night and you trigger mania, e.g. - and a symptom, from early awakenings in depression to hypersomnia in depression to decreased need for sleep in mania. There is obviously more to bp than that, but sleep is a big part.