For others, onset is gradual. Most individuals with bipolar disorder, in fact, experience shorter and more frequent episodes as the illness progresses. Eventually, they may meet criteria for rapid cycling, either temporarily or permanently. According to this theory, episodes are initially triggered by actual or anticipated life events such as the death of a loved one or an upcoming job interview. As the sequence is repeated, however, the affected individual becomes increasingly sensitive to anything that may be a trigger.
Episodes become increasingly frequent and independent of anything outside the patient's brain.
Sometimes, the result of this process may be rapid cycling. Biological Rhythm Disturbances. This theory could then account for the sleep disturbances typical of mania and depression and explain other symptoms as well. SAD is a type of depression that typically develops during the fall and winter months and lessens in intensity or completely subsides during the summer months. This theory proposes that rapid cycling is due to inadequate amounts of thyroid hormone in the brain .