Biological relationships between mania and melancholia.

Although opposite mood and psychomotor disturbances usually occur in mania and melancholia, clinical features may also be shared in common or may be present at the same time in both phases of manic-depressive psychosis. In a parallel fashion, most pharmacological agents are selectively effective in one mood phase (tricyclics and monoamine oxidase inhibitors for depression, and neuroleptics for mania) and frequently precipitate or exacerbate the opposite phase. These agents, therefore, may be affecting biological substrates mediating the opposing phase of affective illness. With the exception of electroconvulsive therapy and lithium chemotherapy, few treatments are effective in both mania and melancholia. It is noteworthy, therefore, that carbamazepine may be useful in the acute and prophylactic treatment of mania and melancholia, including some lithium non-responders and patients vulnerable to tricyclic-induced "mood switches". The clinical and biological effects of carbamazepine will be discussed with special emphasis on its biochemical action and the possible mechanisms by which it might influence biological substrates mediating both phases of manic-depressive illness. In addition, the theoretical implications of the presence of both shared and opposing clinical, pharmacological, and biochemical characteristics of the illness will be discussed.