Neurobiological findings before and during successful lithium therapy of a patient with 48-hour rapid-cycling bipolar disorder.

48-hour rapid cycling is a very rare form of bipolar disorder, characterized by regular periodic changes of mood from one day to the other. We report on a patient who suffered from a 48-hour rapid cycling without a history of bipolar disorder before the abrupt onset of his rapid mood cycles. We present polysomnographic and neuroendocrine findings and the clinical course based on daily self-ratings of mood. Treatment with lithium carbonate effectively reduced the amplitude of the mood cycles. With plasma levels between 0.8 and 1.0 mmol, almost complete remission occurred. An overview on previous reports on the therapeutic effect of mood stabilizers in this rare form of bipolar disorder is presented.