Bipolar I Disorder (BID) might be diagnosed primarily as schizophrenia or major depressive disorder in children and adolescents due to unstable or vague symptoms. The depressive phase not yet followed by a manic or mixed episode in either adults or adolescents may lead to an early misdiagnosis. The concept of mixed episode as a manic episode intruding on previous depressive traits puts emphasis on early managements that may lead to a mixed episode.

Assess of changes in clinical features of BID.

To determine the frequency of mixed and manic phase of BID and assess change in rate of mixed versus manic episode on a year-over-year basis.

Study is a cross sectional study performed on 322 patients diagnosed with BID hospitalized in the psychiatric ward of Imam Hossein Hospital during the years of 1991 to 2006. Each episode was considered as an individual case. A single psychiatrist used DSM IV-TR criteria to differentiate a mixed episode from a manic one.

Among 322 patients, 117 were cases of mixed episode and 205 patients were diagnosed as manic episode. Year-over-year comparisons showed an increasing rate of the diagnosis of mixed episode during the course of the study.

The increased rate of the diagnosis of the mixed episode during the period of the study drives attention to all the probable factors that might have a role on the subsequent changes of the clinical feature of BID toward mixed episode.