How early can Bipolar disorder be diagnosed?

I believe that it can be diagnosed during adolescence, however, if it's an especially severe case, I think that it can be even earlier.

Bipolar disorder can be diagnosed in childhood, but it is a controversial diagnosis as there are similar disorders listed in the DSM 5. On one hand, early intervention and treatment of a disorder is beneficial and can save lives. On the other hand, a diagnosis can be a self-fulfilling prophecy. Many people diagnosed with mental health disorders feel stigmatized, or even tend to increasingly behave in ways that conform to the diagnosis. Even more troubling is that people can be misdiagnosed with bipolar disorder and then prescribed medications that can have deleterious side effects, especially in childhood and adolescence. Bottom line - individuals and caregivers should educate themselves, be prepared to advocate for themselves, and if possible develop a long term relationships with a trustworthy health care provider.

Bipolar disorder is often misdiagnosed for conventional depression because the patients often seek help when they are in low mood and consider themselves functioning / normal during mania. As a result, from the start of the symptoms, usually being starting during teenage and growing in early adulthood, it usually take several years to be diagnosed accurately. On average, it takes 3.5 years for type 1 bipolar disorder according to "Polarity of the First Episode and Time to Diagnosis of Bipolar I Disorder" study (available on National Library of Medicine, on the NIH website). The average age-of-onset is 25. So even if theoretically it is possible to diagnose teenagers, especially with hereditary risk factors, it might prove itself quite rare for the majority.