Comorbidity in pediatric bipolar disorder: prevalence, clinical impact, etiology and treatment.

Background: Research on pediatric bipolar disorder (PBD) is providing a plethora of empirical findings regarding its comorbidity. We addressed this question through a systematic review concerning the prevalence, clinical impact, etiology and treatment of main comorbid disorders involved.

Method: A comprehensive database search was performed from 1990 to August 2014. Overall, 167 studies fulfilled the inclusion criteria.

Results: Bipolar youth tend to suffer from comorbid disorders, with highest weighted mean prevalence rate arising from anxiety disorders (54%), followed by attention deficit hyperactivity disorder (ADHD) (48%), disruptive behavior disorders (31%), and substance use disorders (SUD) (31%). Furthermore, evidence indicates that ADHD and anxiety disorders negatively affect the symptomatology, neurocognitive profile, clinical course and the global functioning of PBD. Likewise, several theories have been posited to explain comorbidity rates in PBD, specifically common risk factors, one disorder being a risk factor for the other and nosological artefacts. Lastly, randomized controlled trials highlight a stronger therapeutic response to stimulants and atomoxetine (vs. placebo) as adjunctive interventions for comorbid ADHD symptoms. In addition, research focused on the treatment of other comorbid disorders postulates some benefits from mood stabilizers and/or SGA.

Limitations: Epidemiologic follow-up studies are needed to avoid the risk of nosological artefacts. Likewise, more research is needed on pervasive developmental disorders and anxiety disorders, especially regarding their etiology and treatment.

Conclusions: Psychiatric comorbidity is highly prevalent and is associated with a deleterious clinical effect on pediatric bipolarity. Different etiological pathways may explain the presence of these comorbid disorders among bipolar youth. Standardized treatments are providing ongoing data regarding their effectiveness for these comorbidities among bipolar youth.