One hallmark of the revolution in psychiatric research begun by the National Institute of Mental Health, as I explored in The Chronicle Review last week, is the sliding scale of the many symptoms that, together, compose the traditional psychiatric disorders. There is no on or off switch for mental illness, researchers say. There is only a dial.
For some disorders this makes intuitive sense; few people balk at the idea of being a little depressed or anxious. We’re human. It comes with the territory. But as the past decade has shown, this “dimensionality” is also seen in symptoms that had long seemed the lonely terrain of the distressed: the hallucinations and delusions tied to schizophrenia.
Indeed, when I asked Bruce Cuthbert, the prime force behind the institute’s project, for an example of the type of research he’d like to foster, his first example—after the work of Peter Lang, his mentor—was the move by a subdiscipline of psychiatrists to study hallucinations and delusions not just in their patients, but in everyone.
What’s now called the “continuum model of psychosis” is perhaps best associated with Jim van Os, a psychiatrist at Maastricht University Medical Center, in the Netherlands. By the mid-1990s, van Os had become convinced that no single gene would be tied to schizophrenia, and that, given the disorder’s complex origins, you could predict a sliding scale of symptoms from it. So when he got word that Holland was conducting a nationwide study on the incidence of psychiatric symptoms, he made certain that it included tests for psychosis.
The results? Out of a representative sample of 7,076 people, 17.5 percent reported some type of hallucination, delusion, or related trait. Psychosis in the traditional sense, however, could be diagnosed in only 2.1 percent of people in the study. Most of the participants could go on and live their lives, and if occasionally they had a hot thought, heard voices, or became fixated or deluded about their self-worth—well, it happens.
It makes sense in retrospect. We all know characters. Van Os recalls hearing of a famous cook who talked about voices giving him new recipe ideas for his restaurants. And there are some people who may not hear voices but sit one step down, possessing a lively inner voice.
“The experiences are quite common in the general population, but of course we only see psychosis when people have problems,” van Os said. “If a voice tells you to hurt yourself, then we see psychosis. If it gives you recipes …”
Let’s be clear about terms. This is not to say that a large slice of the population suffers from the symptoms of serious psychotic disorders. They’re not seeing things—visual hallucinations are rare even for the very ill. And they’re not deluded to the point of believing they’re the star of their own reality television show, or that their loved ones have been replaced by simulacra. But yes, they may hear things.
The continuum of psychosis remains a young discipline, but van Os’s numbers have been replicated in a broad way: It is uncontroversial, for example, for a recent review to estimate that 6 percent to 21 percent of children, along with 10 to 15 percent of adults, are likely to hear “auditory verbal hallucinations” at some point. Refining estimates past that is a challenge, however.
It’s also far from established that the same brain dynamics are at play throughout the continuum. (That’s the type of research the National Institute of Mental Health and Cuthbert want to sponsor, and it’s a hot area of science.) Indeed, prematurely assuming the same causes are at play in subclinical and clinical psychosis could harm the field, making it harder to see unique causes in a clinical case, that same review warned.
Still, a few trends are clear: Men, migrants, ethnic minorities, the unemployed, the unmarried, and the less educated all are more likely to experience hallucinations and delusions, just as they are more likely to suffer from psychotic disorders. And the symptoms are often found in patients suffering from other disorders, like depression.
“Milder psychotic experiences in anxiety and depression are common,” van Os said, even if they’re not factored into those diagnoses. “No clinician will look for delusion in an anxiety or depression patient,” he added.
To me, though, the most important revelation from the continuum of psychosis is, in a way, political. It was once thought that mild psychotic experiences would signal, down the road, full-blown disorders; that the sufferer was bound for a one-way ticket to the country of the ill. And some do go on to suffer severe symptoms, of course. But many others go on to workaday, normal lives, as all around them researchers begin to tear down the fence posts they once erected between the sick and the hale.Return to Top