Predictors of Transition from Child and Adolescent Bipolar Not Otherwise Specified to Bipolar I Disorder, a Longitudinal 3.9-Year Study

<b>Background:</b> Children and adolescents with subthreshold manic symptoms not meeting full DSM criteria for bipolar I or II disorder (BP-I or BP-II) are classified as unspecified bipolar disorder (formerly bipolar not otherwise specified: BP-NOS). Factors associated with transition from BP-II or NOS to BP-I may predict the progression of the disorder. Our objective is to analyze factors associated with transition to BP-I in a Spanish sample of youth with BP-NOS or BP-II. <b>Methods:</b> We included all youth diagnosed with BP before 18 years of age presenting to our clinic (October 1999-December 2014). We assessed clinical factors that may predict transition to BP I with a logistic regression and a multivariable model for data analysis. <b>Results:</b> A total of 72 patients with BP, mean (SD) age 14.5 (10.5-16.0) years, were followed for a median period of 3.9 years. In total, 95.8% of patients retained the BP diagnosis, but they changed type. Baseline BP-I % was 37.5%, and 62.5% at endpoint. BP-NOS decreased from baseline 54.2% to 25% at endpoint. The % of BP-II was 8.3% in both time points, but they were not the same individual patients, as some transitioned from BP-II to BP-I and some BP-NOS changed to BP-II. BP-NOS was stable in 46.1% of patients, but 38.5% transitioned to BP-I over time. Psychotic symptoms during prior depressive episodes (MDD) increased the risk of transition to BP-I by 11-fold. Each individual symptom of mania increased the risk of transition to BP-I by 1.41. <b>Conclusions:</b> BP-NOS was stable in 46.1% of patients, but 38.5% transitioned to BP-I over time. Psychotic symptoms during prior MDD episodes increased the risk of transition from BP-NOS to BP-I.