Objective: To compare clinical characteristics and courses of illness of bipolar I disorder patients in Siriraj Hospital, who were first presented with either manic or depressive episode.

Materials and Methods: One-hundred and fifty participants with bipolar I disorder who were treated during August 2013 and October 2014. They were divided into two groups by their first mood episode: depressive and manic polarity groups. Data were collected by semi-structured interviews, Diagnostic Interview for Genetic Studies [DIGS] Thai version and chart reviews. Clinical characteristics and courses of illness of both groups were analyzed.

Results: There were 94 and 56 patients in the first episode of depressive polarity group and manic polarity group, respectively. The first episode of depressive polarity group had longer durations of illness and higher numbers of depressive episodes and history of suicide attempts. Odds ratio showed that the first episode of depressive polarity increased risk for lifetime history of suicide and poor concentration than the first episode of manic polarity; odds ratio were 3.04 (95% CI 1.45 to 6.37) and 2.78 (95% CI 1.28 to 6.02), respectively.

Conclusion: The polarity of the first episode impact lifetime clinical presentations and illness severity. Physicians should pay attention on concentration and suicide ideality of bipolar I disorder patients whom first presented with depressive episode.

Keywords: Bipolar I disorder, First episode, Polarity, Course of illnesses, Suicide