Maria I of Portugal
Maria I also had two different titles: "Maria the Pious" and "Maria the Mad." She was the first queen in Portugal to rule in her own right (rather than as a regent for a minor or consort). Her reign began in 1777 and lasted for 39 years. Maria I was considered to be a good and competent ruler until becoming delirious in 1786. Her husband Peter III (who was also her uncle) died that year, and her son passed away in 1791 [source: Livermore].
Deeply religious to the point of mania, Maria I was also devastated by the death of her confessor in 1791. She considered herself damned, in turns ranting, raging, screaming and wailing [source: Roberts]. Treatments included bloodletting and enemas -- "purgatives" that were commonly used to treat insanity. The queen did not willingly submit to these, and who can blame her?
Dr. Francis Willis, who had treated George III, came to the court in Portugal and diagnosed her as insane. His treatments were even worse -- straitjacketing, blistering and ice baths. Willis wanted to take her to England, away from the court and priests that he accurately considered to be negative influences on her mental health -- but not surprisingly, the court objected. Her son Prince João took over as regent in 1799. Unfortunately the prince wasn't suited to the job, and the court fled to Brazil after France invaded Portugal. Queen Maria I died there in 1816 [source: Roberts].