“Medical Inquiries and Observations upon the Diseases of the Mind. For years Rush had been investigating the causes of and remedies for madness and other “diseases” of the mind. “The subjects of them have hitherto been enveloped in mystery,” he wrote to Adams. “I have endeavored to bring them down to the level of all other diseases of the human body, and to show that the mind and body are moved by the same causes and subject to the same laws.”