Bipolar disorder usually strikes between the ages of 15 and 25, and is extremely rare in preteens, according to a major study: Age at onset versus family history and clinical outcomes in 1,665 international bipolar-I disorder patients
The findings are old hat. It’s long been known that manic-depression most often begins around the age of 20, give or take a few years. Onset in later life is less common while earlier onset is very unusual.
The main graph could have been lifted from any psychiatry textbooks of the last century:
The red bars are the data. Ignore the black line, that just shows an imaginary ‘even’ distribution over the lifespan.
Why am I blogging about these remarkably unremarkable results? Because they undermines the theory, popular in certain quarters but highly controversial, that ‘child bipolar’ or ‘pediatric bipolar’ is a major health problem.
The study confirmed that early-onset bipolar I does exist, but just 5% of the bipolar I patients had an onset before the age of 15. Assuming a lifetime prevalence of 1% for bipolar I disorder, which is about right, that makes about 0.05%, 1 in 2000 kids, about the same prevalence as Down’s Syndrome. Even that’s an overestimate, though, because this sample was enriched for early-onset cases: some of the participating clinics were child and adolescent only.
There’s a few caveats. This was a retrospective study, that took adults diagnosed bipolar, and asked when their symptoms first appeared. It’s possible that early onset cases were under-sampled, if they were less likely to survive to adulthood, or get treated. The generally milder bipolar II might also be different from the bipolar I studied here. But in general, these numbers support the traditional view that childhood bipolar is just not very prevalent.