From the book titled "The Myths of Innovation" by Scott Berkun-
"The talent for taking two unrelated concepts and finding connections between them is called associative ability. Persons with low associative barriers may think to connect ideas or concepts that have very little basis in past experience or that cannot easily be traced logically. Read that last sentence again: it's indistinguishable from various definitions of insanity. The tightrope between being strange and being creative is too narrow to walk without without occasionally landing on both sides, explaining why so many great minds are lampooned as eccentrics. Their willingness to try seemingly illogical ideas or to make connections others struggle to see invariably leads to judgement (and perhaps putting some truth to stereo types of mad scientists and unpredictable artists.) Developing new ideas requires questions and approaches that most people wont understand initially, which leaves many true innovators at the risk of becoming lonely, misunderstood characters."
I think the difference between creativity and insanity is that the former has lots of ideas and hates all of them, and the second can't help but fall in love with every last one.
I see the difference between creativity and insanity as a function of society. If a given society sees the connections as useful, it's creative. If instead, society cannot make sense of the connections, it's insanity.
As an analogy, mentally challenged children were seen as cursed in ancient Sparta and were routinely put to death. On the other hand, Mayan culture viewed mentally challenged children as "divine gifts," and the children could easily rise to positions of religious prominence and status in adulthood.
It's less a matter of the individual than how that individual can fit into society.
"The talent for taking two unrelated concepts and finding connections between them is called associative ability. Persons with low associative barriers may think to connect ideas or concepts that have very little basis in past experience or that cannot easily be traced logically. Read that last sentence again: it's indistinguishable from various definitions of insanity. The tightrope between being strange and being creative is too narrow to walk without without occasionally landing on both sides, explaining why so many great minds are lampooned as eccentrics. Their willingness to try seemingly illogical ideas or to make connections others struggle to see invariably leads to judgement (and perhaps putting some truth to stereo types of mad scientists and unpredictable artists.) Developing new ideas requires questions and approaches that most people wont understand initially, which leaves many true innovators at the risk of becoming lonely, misunderstood characters."