From the earliest Western philosophers to the most technologically-equipped neuroscientists, the apparent connection between creative genius and mental illness has been a source of fascination and study. In the end, it may be geneticists - aided by the people of Iceland - who show that link is real.
A new study finds that, compared with people employed in occupations not defined as creative, people who pursue careers in writing or visual and performing arts are more likely to carry genetic variations predisposing them to developing psychosis - the kinds of serious disturbances of thinking and emotion seen in schizophrenia and bipolar disorder.
In Iceland, people affiliated with national societies of dancers, writers, musicians and visual artists were 17% more likely than those outside those professions to have a genetic vulnerability to schizophrenia or bipolar disorder than did Icelanders working in other fields.
Data from four large studies conducted in Sweden and the Netherlands - comprising an additional 35,000 people - suggested an even stronger link between genetic propensity to mental illness and creativity: In those, people working in creative fields were 25% more likely than those who were not to carry a strong genetic propensity to develop mental illness. That offered further confirmation of the findings from Iceland.
The new findings, published Monday in the journal Nature Neuroscience, emerged largely from Iceland's DeCode Project. Sponsored by the biopharmaceutical company Amgen, the DeCode Project aims to uncover the genetic bases of diseases and other individual traits by sequencing the entire genomes of close to 3,000 people, partially sequencing the genomes of more than 104,000 others, and cross-referencing those findings with Iceland's comprehensive national health and genealogical records.
Artists, scientists and philosophers have long surmised that the highly creative mind works differently than does the more plodding, methodical mind most of us are issued at birth. Artists seem to see the world differently, to process sensory experiences differently, to conceptualize problems and their solutions differently.
But while creativity is easy to spot, it is hard to define. And the line between eccentricity and mental illness is unclear and ever-shifting. So demonstrating that a link between creativity and mental illness actually exists has been a maddening task.
Leave it to population genetics - a field of diabolical complexity - to draw a line between madness and the creative mind.
In recent years, genome-wide association studies have identified a passel of genetic variants that seem to confer susceptibility to schizophrenia and bipolar disorder in those who carry them. But not all whose genes spell a vulnerability to severe mental illness develop delusional thinking, hallucinations or fractured modes of thought. Other factors - early life experiences, mental and physical stressors, even viral infections - also play a role.
In past genetic surveys, the Icelandic authors of the new research have shown that, even without a diagnosis of mental illness, many unaffected carriers of these gene variants do share some of the cognitive abnormalities of people who suffer from psychotic disorders. Many relatives of a person with overt mental illness, for instance, will carry a genetic vulnerability to such disease; their way of thinking and the way they process emotions may be unusual, but they're not dysfunctional.
With unusual frequency, the current study suggests, these people tend to find their way into occupations in which their unusual ways of thinking find outlets that are valued by society. They write poetry, translate feelings into movement or music, or create art that reflects the human condition.
In the large populations studied - more than 120,000 people in all - the choice to pursue a creative occupation or to enter such occupations as farming, sales, business management or manual labor could not be accounted for by differences in IQ, educational attainment or how closely an individual was related to someone with schizophrenia or bipolar disorder.
Clearly, the creative professions are peopled by many without a genetic propensity to mental illness. And just as clearly, many with such a propensity to mental illness become farmers, salesmen and business executives. But the authors of the current study note that the power of mental illness vulnerability genes to drive carriers into creative professions trumps family traditions or national cultural values.
"Our study lends support to direct influences of genetic factors on creativity as opposed to sharing an environment with individuals with psychosis influencing creative aptitude," the authors wrote.