The mistreatment of mentally ill people
The overarching theme of Ten Days in a Mad-House is the mistreatment of mentally ill people. In the book, author Nellie Bly illuminated some of the awful things many patients at the insane asylum she was committed to had to deal with, including physical abuse, mental abuse, and other torturous activities. In writing first the articles and then this book, Bly aimed to reform this broken system and create better conditions for those who were justly and unjustly committed to insane asylums.
Reforming broken systems
A common, reoccurring, and powerful theme in Ten Days in a Mad-House is reforming broken systems. Specifically, Bly strongly advocated for the reformation of the mental health system in New York and the United States as a whole after experiencing its horrors firsthand. Along with the paycheck she earned from writing the articles that became Ten Days in a Mad-House, it was Bly's biggest goal to reform such a broken system.
The conflict between doctors and their patients
A fairly significant theme in the book is the conflict between doctors and their patients. On one hand, doctors purport to have the best interests of their patients at heart. On the other, the patients want to get better and most want to leave the asylum (many are also very clearly not mentally ill). The doctors, many of whom don't want to see their patients get better and leave, are thus at odds with the patients.
Behaving normally in an abnormal situation
After Bly completes her ruse and is committed to the asylum, she begins to act normally. A vitally important theme in the book is thus behaving normally in an abnormal situation, which Bly certainly does. However, rather than being treated normally, Bly is treated as if she were crazier than ever.