Parry P, Allison S, Bastiampillai T.

Child and Adolescent Mental Health. 17 July 2017. DOI: 10.1111/camh.12231

This re-examination of 12 studies included in a 2011 review by Van Meter et al  (doi: 10.4088/JCP.10m06290) finds that the previously reported rate of paediatric bipolar disorder of 1.8% was grossly over-estimated.  The inclusion of few participants under 12 years of age, discrepancies between US and non-US study results, and combination of parent and child report data despite obvious discrepancies, leads the authors of this review to conclude that the actual incidence of bipolar disorder in samples of children under 12 years old is close to zero.

http://onlinelibrary.wiley.com/doi/10.1111/camh.12231/abstract