It depends who you ask. It's "controversial". Some say that, like schizophrenia, bipolar strikes in adolescence or after, and that pre-pubertal onset is extraordinarily rare. Others say that kids can be, and often are, bipolar, but their symptoms may differ from the ones seen in adults. You know a 20 year old's manic when they stay up for 3 days straight writing a book about how God's chosen them to save the world. A "bipolar" 10 year old, though, is more likely to show irritability and mood swings. Critics say that this isn't evidence of bipolar, it's evidence of... irritability and mood swings. Or, indeed, of being 10.
But what's not always appreciated is how new the concept of pediatric bipolar as a common disorder is, and how specific it is to American psychiatry. Here are a few graphs I put together to illustrate this, based on numbers of scientific publications.
First up, when did people start talking about it? Here's the number of PubMed hits for pediatric bipolar each year. As you can see, it was rarely talked about before the year 2000, after which its popularity shot up rapidly; it seems to have plateaued now, but it's hard to tell.
In fact, the true trend is even more dramatic, because many of the early hits were not about psychiatry at all. For example, in 1999, 5 of the 10 were nothing to do with manic-depression. One was about the growth pattern of a certain kind of bacteria (they're "bipolar", because they have two poles of growth.)
Is the post-2000 spike just a reflection of the fact that people are publishing more papers about bipolar in general? No. Here's a graph showing pediatric bipolar hits as a fraction of all "bipolar disorder" hits for that year. It's been rising for a while and it's now 5%.
Where are these publications coming from? America. Taking the first two pages of PubMed hits for pediatric bipolar, and excluding the non-psychiatric ones, 30 are from the USA, and just 4 are from elsewhere. For "bipolar disorder", it's 13 vs. 25. (This is in terms of the affiliation listed for the primary authors of the study.)
What about paediatric bipolar, the British spelling? It's almost unheard of. There are only 53 PubMed hits in total, as against 564 for pediatric bipolar. Of the first 20 hits, 9 are non-psychiatric, and 3 are from an Australian journal, criticizing the American concept of pediatric bipolar!
It's remarkable that the monthly British Journal of Psychiatry has never published a paper about "pediatric bipolar" or "paediatric bipolar": if you search their archives you get just 5 hits, and they are all in the references sections, not the papers themselves. The monthly American Journal of Psychiatry has published 37 papers mentioning "pediatric bipolar", of which 25 are not just in the references, and 10 are in the titles.
So, at least in terms of the literature, pediatric bipolar is overwhelmingly a 21st century American phenomenon. It barely existed before 2000, and it barely exists elsewhere. This corresponds to what some non-American psychiatrists have observed. In The Paediatric Bipolar Hypothesis: The View from Australia and New Zealand, Australian psychiatrists Peter Parry, Gareth Furber and Stephen Allison point out that
Pediatric bipolar has certainly become more common as a diagnosis in the USA recently - a 40-fold increase in 12 years up to 2003:
Traditionally, bipolar affective disorder has been considered rare in children and uncommon in adolescence ... However paediatric bipolar disorder (PBD) has become a topical issue in child and adolescent psychiatry over the last decade, driven by research in the USA. The proponents of PBD are concerned that the traditional approach to bipolar disorder in children and adolescents is missing a large number of distressed children, whose course of bipolar illness could be ameliorated or attenuated by early treatment.
Whereas elsewhere, it's still regarded as incredibly uncommon...
The number of visits to primary care physicians in the under 20 age group where the diagnosis was bipolar disorder increased from 0.01% in 1994/5 to 0.44% in 2002/3
Parry, Furber and Allison then present the results of a survey of 199 child and adolescent psychiatrists in Australia and New Zealand.
Soutullo et al. reported that none of the 2,500 children 10 years or younger referred to the Royal Manchester Children's Hospital ... had a diagnosis of mania or bipolar disorder ... A more recent German survey revealed German child and adolescent psychiatrists were largely holding to a traditional stance as only 8% claimed to have diagnosed a pre-pubertal child with bipolar disorder.
Of course this is just a survey, but the results are striking.
The majority of participants (53.4%) said they had never seen a case of pre-pubertal bipolar disorder, whilst a further 28.5% estimated they'd seen only 1 or 2 cases. Only 35 participants (18.2%) estimated having seen 3 or more cases of pre-pubertal bipolar disorder. ... Most participants (83.1%) were of the opinion that bipolar disorder in pre-pubertal children was either "very rare (less than 0.01%)", "rare (less than 0.1%)", or "cannot be diagnosed in this age group".
Peter Parry reports as a conflict-of-interest that he's a member of Healthy Skepticism, who are, in their own words, in the business of "Improving health by reducing harm from misleading drug promotion". I'm sure neither he nor I need to spell out why drug companies might conceivably have an interest in promoting the concept of pediatric bipolar disorder, given the wide range of drugs available for bipolar adults...
Parry, P., Furber, G., & Allison, S. (2009). The Paediatric Bipolar Hypothesis: The View from Australia and New Zealand Child and Adolescent Mental Health, 14 (3), 140-147 DOI: 10.1111/j.1475-3588.2008.00505.x