[What is cyclothymia?]

The term "cyclothymia" is being used with different meanings. DSM-IV and ICD-10 define "cyclothymia" or "cyclothymic disorder" as a long lasting, subeffective disorder with frequent shifts between hypomanic and (sub)depressive states. In the tradition of Kurt Schneider cyclothymia was understood as a synonym for manic-depressive illness exclusively, while different personality typologies speak of a "cyclothymic" typus. Historically, the term was first used by the German psychiatrist Ewald Hecker in 1877. The definitions of DSM-IV and ICD-10 seem to be satisfactory in respect to reliability, but the nosological position of "cyclothymic disorder" is unclear. We review results concerning clinical symptomatology, comorbidity, biological parameters, personality (including the question of creativity), psycho- and pharmacotherapy as well as clinical course, which leave many questions open. Nevertheless, results in family studies support the idea that at least a fraction of "cyclothymia" is a mild or subclinical form of bipolar disorders. Until further research, which is urgently needed, we suggest that the term "cyclothymia" should be only used according to the guidelines of DSM-IV and ICD-10.