Bipolar disorder is presenting at a younger ageof onset. In the past, many children with bipolar disorder wereundiagnosed and ended up in juvenile detention centers. These childrenwere also often misdiagnosed with severe attention-deficit/hyperactivitydisorder (ADHD) or conduct disorder. In addition, an increasedprevalence rate of substance use disorders and possibly stimulantprescriptions may be responsible for the shift in age of onset ofbipolar disorder. The most compelling epidemiological observations havecome out of the Netherlands, where they typically treat ADHDbehaviorally rather than with stimulants. Childhood bipolar disorderremains unidentified in the Netherlands despite aggressive searching,whereas adolescent and adult bipolar disorder has been found in numberssimilar to those in the United States. This providescross-sectional epidemiological evidence that stimulants may be shiftingthe age of onset in patients who are presenting with potentiallyprodromal bipolar symptoms. Lastly, several researchers speculate thattrinucleotide repeats in the DNA (deoxyribonucleic acid) may beresponsible for so-called genetic anticipation phenomenon, by whichexpansion of trinucleotide repeats in successive generations may beshifting the age of onset to an earlier age. These are just some of themechanistic possibilities for why we are seeing a shift in the age ofonset of bipolar disorder.

Lewinsohn and colleagues found thatthe lifetime prevalence of adolescent bipolar I and II disorder is ~1%,with a 5% lifetime prevalence rate of subsyndromal bipolar disorder.Many symptomatic children and adolescents do not meet full durationcriteria for a hypomanic or manic episode, or they may be one symptomshort of meeting criteria for the disorder.