Each of these disorders may involve a depressive episode, manic episode, mixed episode, hypomanic episode or a combination of any two different episodes. Thus a Bipolar I disorder is characterized by one or more manic or mixed episodes usually accompanied by a depressive episode while a Bipolar II disorder is characterized by one or more Major depressive episodes accompanied by at least one hypomanic episode.

Further classification could involve determining whether the cause is primary or secondary and from here the terms primary mania or secondary mania evolve [11]. One can differentiate mania based on the cause by dividing it into primary or idiopathic mania and secondary mania (where there is an identifiable cause.) This classification of primary and secondary mania was first suggested by Robins and Guze in 1972 [12] and improved by Klerman and Barret and later Krauthemmer in 1978 [13]. However the distinction of primary versus secondary disorders was first muted by Alistair Munro.

Initially secondary mania was described by Robins and Guze as mania occurring in patients who had no previous or concurrent psychiatric illness. Klermman and Barret later described it as an illness following past history of medical, traumatic or pharmacological complaints and use. Krauthemmer took the concept further to describe secondary mania as mania that can occur in association with organic dysfunction – medical and pharmacological toxic – in patients with no history of affective disorder. He was also the first to describe the clinical characteristics of secondary mania being different from primary mania where he noticed that patients of secondary mania were older with no family history of mania. The concept of secondary mania is that a patient can present with symptoms that are similar to the diagnostic criteria for primary mania but with an identifiable cause. In some cases the clinical characteristics are different. Thus HIV secondary mania became to be recognized as a disorder of HIV infective brain degeneration.