When assessing an adolescent with bipolar disorder, what are some of the diagnostic and treatment challenges the clinician might face?  Bipolar disorder is a serious mental health disorder that is often first diagnosed during young adulthood or adolescence. Symptoms of the illness, however, also can appear in early childhood. Although once thought rare in children, diagnosis of bipolar disorder in children has significantly increased over the last decade (Papolos & Bronsteen, 2018). Despite the increased diagnosis of bipolar disorder in children, assessment and diagnosis remain challenging and controversial. This is, in part, because of the lack of research on this disorder in children and adolescents and the growing recognition that the disease can present differently in children from how it presents in adults (AACAP, 2019). Over the years, more attention has focused on the unique presentation of bipolar disorder in the young that has introduced new ways of looking at this disease and assessing it in children.  The importance of identifying the presence of bipolar disease at an early age is highlighted by data showing that adults in whom bipolar disease started at an early age have a more severe course of the illness compared with adult-onset disease. Early-onset disease is associated with a higher risk of suicide; severe mood lability and polarity; lower quality of life and greater functional impairment; higher rates of comorbidity; and a higher risk of substance use disorders compared with adult-onset disease (Papolos & Bronsteen, 2018). Although some children meet the criteria established for adults categorized in the DSM-5, many children fall outside these classical categories, and diagnosis in these children is particularly challenging and difficult (APA, 2013). For these children, additional information beyond what is provided in the DSM may help make an accurate diagnosis which causes increased challenges in assessment and diagnosis.  References Papolos, D, & Bronsteen A. (2018) bipolar disorder in children: assessment in general pediatric practice. Curr Opin Pediatr, 25(3):419-426. American Academy of Child and Adolescent Psychiatry (AACAP). (2019) bipolar disorder: Parents’ Medication Guide for Bipolar Disorder in Children & Adolescents.  American Psychiatric Association (APA) (2013). Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Washington, DC: American Psychiatric Association.