...I have spent much of my career focusing on the neuroscience of mental illness, but in recent decades I’ve also focused on what we might call the science of genius, trying to discern what combination of elements tends to produce particularly creative brains. What, in short, is the essence of creativity? Over the course of my life, I’ve kept coming back to two more-specific questions: What differences in nature and nurture can explain why some people suffer from mental illness and some do not? And why are so many of the world’s most creative minds among the most afflicted? My latest study, for which I’ve been scanning the brains of some of today’s most illustrious scientists, mathematicians, artists, and writers, has come closer to answering this second question than any other research to date.

The first attempted examinations of the connection between genius and insanity were largely anecdotal. In his 1891 book, The Man of Genius, Cesare Lombroso, an Italian physician, provided a gossipy and expansive account of traits associated with genius—left-handedness, celibacy, stammering, precocity, and, of course, neurosis and psychosis—and he linked them to many creative individuals, including Jean-Jacques Rousseau, Sir Isaac Newton, Arthur Schopenhauer, Jonathan Swift, Charles Darwin, Lord Byron, Charles Baudelaire, and Robert Schumann. Lombroso speculated on various causes of lunacy and genius, ranging from heredity to urbanization to climate to the phases of the moon. He proposed a close association between genius and degeneracy and argued that both are hereditary.

Francis Galton, a cousin of Charles Darwin, took a much more rigorous approach to the topic. In his 1869 book, Hereditary Genius, Galton used careful documentation—including detailed family trees showing the more than 20 eminent musicians among the Bachs, the three eminent writers among the Brontës, and so on—to demonstrate that genius appears to have a strong genetic component. He was also the first to explore in depth the relative contributions of nature and nurture to the development of genius.

“Doing good science is … like having good sex. It excites you all over and makes you feel as if you are all-powerful and complete.”

As research methodology improved over time, the idea that genius might be hereditary gained support. For his 1904 Study of British Genius, the English physician Havelock Ellis twice reviewed the 66 volumes of The Dictionary of National Biography. In his first review, he identified individuals whose entries were three pages or longer. In his second review, he eliminated those who “displayed no high intellectual ability” and added those who had shorter entries but showed evidence of “intellectual ability of high order.” His final list consisted of 1,030 individuals, only 55 of whom were women. Much like Lombroso, he examined how heredity, general health, social class, and other factors may have contributed to his subjects’ intellectual distinction. Although Ellis’s approach was resourceful, his sample was limited, in that the subjects were relatively famous but not necessarily highly creative. He found that 8.2 percent of his overall sample of 1,030 suffered from melancholy and 4.2 percent from insanity. Because he was relying on historical data provided by the authors of The Dictionary of National Biography rather than direct contact, his numbers likely underestimated the prevalence of mental illness in his sample...