Here's a puzzle: Since schizophrenia is highly heritable, and since those who suffer it have low reproductive success, why hasn't its prevalence diminished over time? That's what evolutionary theory suggests should occur. Yet this debilitating mental illness appears to have afflicted human beings for millennia and persists at an unwavering rate of about one percent worldwide. How can this be?
Rachael Grazioplene, a Ph.D. candidate in psychology, has an answer: "It seems that schizophrenia, like bipolar disorder, is a secondary consequence of genes that also produce positive human traits," she says. "In healthy individuals, these genes are linked to enhanced creativity. This suggests that the same biological underpinnings that cause delusions in some people give rise to ingenuity in others."
There's plenty of evidence to back up that idea, Grazioplene says, including a 2011 study from Sweden of 300,000 people with serious mental illness. The findings show that healthy siblings of people with bipolar disorder and schizophrenia are especially likely to work in creative occupations. This could explain how genes linked to schizophrenia persist across generations. While psychosis minimizes opportunities to procreate, creativity most likely increases both survival and reproductive prospects.
Yet what, exactly, does creativity have in common with psychosis -- besides a smattering
of special genes? Just how are the people who occupy these two very different "camps of perception" alike? Grazioplene's doctoral work in the psychology department's Personality, Individual Differences, and Behavioral Genetics program seeks answers to these questions both in terms of behavior and the brain.
Making sense of experience
Describing the shared behavior is easy: both groups show a high propensity to perceive unrelated details as meaningfully connected, a tendency called apophenia. A byproduct of the brain's programming to make sense of experience, this phenomenon touches all of us in some way: "This is what's happening when you hear your name called out in a noisy crowd," Grazioplene says, "or see the face of Jesus in a pancake."
Apophenia is an expression of the personality trait known as "openness to experience," which describes the general tendency to be imaginative, curious and intellectual. People who rank very high for apophenia and openness are prone to fantasy, says Grazioplene, and have difficulty distinguishing dreams from reality. "They tend to hyperassociate, to see meaning at levels most people don't detect. In itself, this isn't a negative thing. At optimal levels, some of the cognitive processes that lead to disorganized thought may actually be beneficial. Part of what makes people brilliant is that ability to make unlikely connections."
Are these shared behavior characteristics detectible in the brain? There's reason to think so. "If we're right that creativity arises from the same genes that cause psychotic illness," says Grazioplene, "we'd expect to see not only that the personality traits linked to these genes are similar, but that the associated brain structure will be shared as well."
That's just what the early research seems to show. Grazioplene's research with advisor Colin DeYoung shows that people who rank high for apophenia /openness have more diffusely connected white matter -- the stuff that makes up the cerebral wiring system -- in specific brain regions. Interestingly, the patterns they've discovered resemble those found by other researchers in the brains of people with schizophrenia and bipolar disorder.
That's not the end of the story, though. In addition to identifying similarities between creative individuals and people with psychosis, Grazioplene is keen to understand the differences.
"There's this great study showing that successful artists are as high as schizophrenics on these measures of unusual thought processes and strange experiences," says Grazioplene, "but that they don't have any of these more negative symptoms such as cognitive disorganization, confusion, flattened emotional affect, anxiety. What it suggests to me is that while there are certain shared network properties between schizophrenia and creative artistic professions, there are other divergent characteristics."
One thing that appears to dampen vulnerability to psychosis is intelligence: "It seems to have a modulating effect on apophenia," says Grazioplene. "In order to usefully engage the hyper-associative process, you have to have the top-down executive control to choose among all these alternatives to identify what's actually meaningful and which things are by chance."
Discovering such protective factors is Grazioplene's ultimate goal. She's seeking them by studying personality findings and brain images from 300 subjects, none of whom has been diagnosed with psychotic-spectrum disorders. Studying normal individuals, she hopes, will shed light on the question that interests her most: "What is it about the brains of healthy people with very high apophenia that protects them from developing the disorganizing symptoms of, for example, schizophrenia?"
In it for the long haul
This is the sort of question that can take a lifetime to answer, but Grazioplene seems to be in for the long haul. "Many people wonder if there's a strict level -- an identifiable point -- at which a person becomes a schizophrenic," she notes. "What we're finding from the biology is that the answer is no. The biology of the brain is showing us that there is a very gradual curve between normal and abnormal for these illnesses."
For Grazioplene, the notion that the liability for psychotic spectrum disorders is spread throughout the population raises a profound question: how does this liability actually play out at the neurobiological level? Ultimately, she says, "understanding the neural mechanisms that create resilience, despite the presence of high risk, is a very important goal in the understanding and treatment of these illnesses."
In the meantime, Grazioplene says, it may make sense to view disorders of perception in more nuanced terms. "Stories of mental health and illness are really never a matter of a few straightforward cause-and-effect circumstances," she says. "There are no simple answers."
Kate Stanley, B.A. '80, journalism, writes about law, medicine, social policy and global affairs. She was previously a member of theStar Tribune editorial board, and as an undergraduate was editor-in-chief of the Minnesota Daily.