Treatment-resistant, defined as a history of unsuccessful trials of lithium (documented level of greater than 0.8 mEq/L), valproic acid (documented level of greater than 50 ug/ml), carbamazepine (documented level greater than or equal to 6 ug/ml), a neuroleptic as well as a combination of two of these agents. Each trial must have been at least 6 weeks long. A trial will be considered unsuccessful if the medication was discontinued because of intolerable side-effects.