<P> The first diagnostic distinction to be made between manic - depression involving psychotic states, and that which does not involve psychosis, came from Carl Gustav Jung in 1903 . Jung's distinction is today referred to in the DSM - IV as that between' bipolar I' (mania involving possible psychotic episodes) and' bipolar II' (hypomania without psychosis). In his paper Jung introduced the non-psychotic version of the illness with the introductory statement, "I would like to publish a number of cases whose peculiarity consists in chronic hypomanic behaviour" where "it is not a question of real mania at all but of a hypomanic state which cannot be regarded as psychotic". Jung illustrated the non-psychotic variation with 5 case histories, each involving hypomanic behaviour, occasional bouts of depression, and mixed mood states, which involved personal and interpersonal upheaval for each patient . </P> <P> After World War II, John Cade, an Australian psychiatrist, was investigating the effects of various compounds on veteran patients with manic depressive psychosis . In 1949, Cade discovered that lithium carbonate could be used as a successful treatment of manic depressive psychosis . Because there was a fear that table salt substitutes could lead to toxicity or death, Cade's findings did not immediately lead to treatments . In the 1950s, U.S. hospitals began experimenting with lithium on their patients . By the mid-60s, reports started appearing in the medical literature regarding lithium's effectiveness . The U.S. Food and Drug Administration did not approve of lithium's use until 1970 . </P> <P> The term "manic - depressive reaction" appeared in the first American Psychiatric Association Diagnostic Manual in 1952, influenced by the legacy of Adolf Meyer who had introduced the paradigm illness as a reaction of biogenetic factors to psychological and social influences . Subclassification of bipolar disorder was first proposed by German psychiatrist Karl Leonhard in 1957; he was also the first to introduce the terms bipolar (for those with mania) and unipolar (for those with depressive episodes only). </P> <P> In 1968, both the newly revised classification systems ICD - 8 and DSM - II termed the condition "manic - depressive illness" as biological thinking came to the fore . </P>

When was bipolar disorder first recognized as a psychological disorder