King George III of England and Queen Maria I of Portugal: bipolar disorder and prince regents as common features of their reigns

Humanity is sporadically subjected to leaders with deviant behavior, ego problems, or psychiatric disorders, potentially leading to social instability. Bipolar disorder is not common in all populations, but, coincidentally, studies suggest that it affected two sovereigns that were contemporaries, King George III of England, who died 201 years ago, and Queen Maria I of Portugal, who died 205 years ago. They lived during a time when Europe was in turmoil with the French Revolution and Napoleonic Wars, which also coincided with the rise of psychiatry. Both monarchs were forced to have prince regents rule in their place, due to their emotional decline, and they shared the same medical consultant, Francis Willis.