Robert Burnham displayed several hallmarks of mental illness. If you look at his life after he graduated from high school, his first job, and his devotion to collecting scientific data, you can see that he was not a person who budged out of an existing structure (or rut) in his life. He was clearly most happy with defined goals, and a repetitive set of tasks that he could successfully accomplish. (They need not be the same task, nor do they have to be mindless, they simply have to have a clearly defined "map" that one can follow to solve the problems.) A highly structured life is often key to a mentally ill person's ability to live a more normal life. Lowell Observatory provided that structure for Burnham for many years. When that job ended, Burnham was deeply entrenched in that structure, and was unable to create another one. While he had a stream of income from the royalties, he could continue his same life of observing and writing, outside of the observatory. When the income dried up, he was lost. Often, a spouse or close family member can help a person create another, but Burnham's illness was not recognized as such. While his family was supportive, they did not know what he was dealing with, nor that he had passed the point where he could, himself, find a new "rut" and settle into it. Left without his structured life, he was unable to cope. His illness progressed rapidly, and he was incapable of handling the chaos of everyday life. None of this is to deny his genius, he clearly had a passionate love of what he was doing. He melded his love of philosophy with the repetitive nature of observing, to create the handbook we all have and love today. But with his genius, he had a mental illness that was not commonly recognized, and that, by its very nature, made him incapable of seeking help himself.