Objective: To investigate the prevalence of mixed episodes during the course of illness in bipolar disorder.
Method: A total of 1620 patients with an ICD-10 diagnosis of bipolar affective disorder at the first psychiatric contact were identified in a period from 1994 to 2003 in Denmark and the prevalence of mixed, depressive and hypomanic/manic episodes were calculated at each episode.
Results: The prevalence of mixed episodes increased from the first episode to the tenth episode, however, only for women (6.7% of the first episodes leading to psychiatric care compared with 18.2% of the tenth episodes). For men, the prevalence of mixed episodes was constantly low. At all episodes, the presence of a current mixed episode increased the risk substantially of getting a future mixed episode.
Conclusion: Clinicians should pay more attention to mixed episodes, especially among women, as they may represent an increasing treatment challenge as the illness progress.