Abstract
As indicated in previous chapters, a complete understanding of bipolar disorder remains elusive, particularly with an early-onset of the disorder. As such, an accurate accounting of how common this disorder is in the general population also remains to be unequivocally made. However, a recent meta-analysis of epidemiologic, community-based studies has estimated the prevalence of an early-onset bipolar disorder to be approximately 1.8% (Van Meter, Moreira, & Youngstrom, 2011). As subthreshold cases are included, estimates increase to 6–7% (see Van Meter, Moreira, et al., 2011 for studies included in this meta-analysis). These subthreshold cases are particularly important as research has demonstrated that a substantial majority—almost half—of these individuals will convert to a bipolar I or bipolar II diagnosis in their youth (Axelson et al., 2011).