The 40-fold increase in children who receive a diagnosis of bipolar disorder has generated great concern. Some believe it represents an over-diagnosis of a serious condition whose boundaries have become fuzzy and thereby confers upon children unnecessary, inappropriate, and harmful labels and medication. To the degree that this occurs, it is indeed a serious problem that warrants correction.
While we certainly wish that NO children would experience the very difficult symptoms associated with bipolar disorder, citing the increase of diagnoses as 40-fold may be an alarmist way to think of the situation.
According to a study conducted in 2007 by Moreno et al., the estimated annual number of office-based visits in which children received a diagnosis of bipolar disorder increased from 25 (1994-1995) to 1003 (2002-2003) visits per 100,000 population. It is true that the statistic does indicate a 40-fold increase. However, it is relevant to note that the dates looked at in the study fall prior to, and after, the creation of the DSM classification of BP-NOS; the classification given to most children. (see What is Juvenile Bipolar Disorder) This makes all the difference to what might otherwise be considered an alarming statistic.
Clearly creation of the BP-NOS classification reflected the growing recognition that children who are severely ill, and who had previously been left out, needed diagnostic recognition. So it is not surprising that, once the classification became available, there was a rapid increase in the diagnosis. Understandably, any increase from zero will seem to be disproportionately large.
In 2011, Van Meter et al compiled data from 12 epidemiological studies, conducted between 1985 and 2007, which looked at the prevalence of mania and hypomania in children . Together the studies accounted for 16,222 children between the ages of 6 and 17. Half of them took place in the United States while the other half were from other countries around the world.
The analysis determined that the overall rate of bipolar disorder in children was 1.8%; a rate that is higher than commonly acknowledged. But it also determined that there was no evidence of an increase in rates of bipolar disorder in the community over time nor were there significant differences between the US samples and the non-US samples.
There is no doubt that some children who do not have bipolar disorder are being diagnosed as such and this is, of course, a concern. But many studies show that under-diagnosis of serious, debilitating, illness which does not meet DSM criteria is far more prevalent than over-diagnosis in the adult community. We believe it is likely to be the same for children.
 Moreno C, Laje, G, Blanco, C, Jiang, H, Schmidt, A.B, & Olfson, M: (2007). National trends in the outpatient diagnosis and treatment of bipolar disorder in youth. Archives of General Psychiatry, 64:1032–1039
 Angst J: (1998). The emerging epidemiology of hypomania and bipolar II disorder. J of Affective Disorders, 50:143-151
 Van Meter AR, Moreira AL, Younstrum EA: (2011). Meta-analysis of epidemiologic studies of pediatric bipolar disorder. J Clin Psychiatry. Sep;72(9):1250-6. Epub 2011 May 31