The morbidity of subthreshold pediatric bipolar disorder: A systematic literature review and meta-analysis.
OBJECTIVE: The objective of this study was to evaluate the morbidity of subthreshold pediatric bipolar (BP) disorder. METHODS: We performed a systematic literature search in November 2017 and included studies examining the morbidity of pediatric subthreshold BP. Extracted outcomes included functional impairment, severity of mood symptoms, psychiatric comorbidities, suicidal ideation and behaviors, and mental health treatment. We used meta-analysis to compute the pooled standardized mean difference (SMD) for continuous measures and the pooled risk ratio (RR) for binary measures between two paired groups: subthreshold pediatric BP vs controls and subthreshold pediatric BP vs pediatric BP-I. RESULTS: Eleven papers, consisting of seven datasets, were included. We compared subthreshold pediatric BP (N = 244) to non-BP controls (N = 1125) and subthreshold pediatric BP (N = 643) to pediatric BP-I (N = 942). Subthreshold pediatric BP was associated with greater functional impairment (SMD = 0.61, CI 0.25-0.97), greater severity of mood symptomatology (mania: SMD = 1.88, CI 1.38-2.38; depression: SMD = 0.66, CI 0.52-0.80), higher rates of disruptive behavior (RR = 1.75, CI 1.17-2.62), mood (RR = 1.78, CI 1.29-2.79) and substance use (RR = 2.27, CI 1.23-4.21) disorders, and higher rates of suicidal ideation and attempts (RR = 7.66, CI 1.71-34.33) compared to controls. Pediatric BP-I was associated with greater functional impairment, greater severity of manic symptoms, higher rates of suicidal ideation and attempts, and higher rates of mental health treatment compared to subthreshold pediatric BP. There were no differences between full and subthreshold cases in the severity of depressive symptoms or rates of comorbid disorders. CONCLUSIONS: Subthreshold pediatric BP disorder is an identifiable morbid condition associated with significant functional impairment including psychiatric comorbidities and high rates of suicidality.