To examine whether positive and negative life events precede bipolar mood symptoms or whether bipolar mood symptoms precede life events in bipolar I and bipolar II outpatients.

173 bipolar outpatients with a diagnosis of bipolar disorder type 1 (BD I) or 2 (BD II) were assessed every three months for a total of two years. Life events were assessed by Paykel's self-report questionnaire. The NIMH monthly retrospective life chart method (LCM-r) was used to assess monthly functional impairment due to manic or depressive symptomatology. Mood symptoms were assessed every six months with the Quick Inventory of Depressive Symptomatology- Self Report (QIDS) and the Young Mania Rating Scale (YMRS).

Multilevel regression analyses (linear mixed-models) showed that negative life events are significantly associated with both subsequent severity of mania and depressive symptoms and functional impairment, whereas positive life events only preceded functional impairment due to manic symptoms and mania severity. These associations were significantly stronger in BD I patients compared to BD II patients. For the opposite temporal direction, we found that mania symptoms preceded the occurrence of positive life events and depressive symptoms preceded negative life events.

Life events appear to precede the occurrence of mood symptoms and functional impairment, and this association is stronger in BD I patients. Mood symptoms also precede the occurrence of life event, but no differences were found between BD I and II patients.