In a new book, out this month, a University of Pennsylvania sociology professor addresses the complex subject of the accurate classification and treatment of psychiatric disorders.

In The Diagnostic System: Why the Classification of Psychiatric Disorders Is Necessary, Difficult and Never Settled, Jason Schnittker, a professor of sociology and research associate at Penn’s Population Studies Center, provides a study of the ongoing disputes surrounding the Diagnostic and Statistical Manual of Mental Disorders, commonly referred to as the DSM.

“No edition of the DSM has provided a fully satisfying system for the classification of psychiatric disorders, in part because of the many different interests and aims the manual is trying to serve,” Schnittker said, adding that the definitions that are useful for mental-health professionals are less useful for scientists. And while its definitions that are more suitable for scientific purposes can sometimes cut against what’s most useful for clinicians, use by the public introduces another complication.

“The public is trying to understand something far more personal, namely if some behavior or feeling is a sign of illness,” said Schnittker. “However, public conceptions of mental illness do not align neatly with what the DSM provides.”

Revising the diagnostic criteria, he said, often serves the interests of one group at the expense of another, and the system itself leaves people feeling unsatisfied.

The DSM’s critics point to its many weaknesses, especially that it is “socially constructed,” Schnittker said.

While he does not disagree with this, he said it is time to take the next step by asking the questions that will advance its purpose: “What else can we do to define something so complex? And, if we accept that our definitions will not be given in nature, what sort of concepts and values should our definitions be based on? Answering these questions requires thinking about what we want the DSM to accomplish and proceeding from there.”

Part of the problem, Schnittker said, is the ongoing belief that a better diagnostic tool is just around the corner. For example, the idea that, with the best available brain scanning technology, researchers could better understand depression at a neurological level and have the perfect diagnostic instruments that do not rely solely on a patient’s symptomatic reports of sadness.

But, it’s not that simple.

“The science surrounding psychiatric disorders has grown enormously over the last four decades, but science can’t always obviate the responsibility of judgement,” Schnittker said. “For instance, we must decide when sadness tips into major depression or when someone’s anxiety is more than a normal amount of worry given the uncertainty of everyday life.”

He said part of what he wants to accomplish with The Diagnostic System, is to have people not only take those decisions seriously but also debate them in the same manner researchers debate the causes of psychiatric disorders, for example.

Even though everyone insists definitions should be more valid, Schnittker said that it becomes increasingly tough to establish what exactly a valid definition of psychiatric disorders should look like.

“A perfect taxonomy of mental-health disorders is likely to remain elusive,” he said. 

A medical sociologist who defines “health” broadly, Schnittker, who joined Penn’s faculty in the School of Arts & Sciences in 2001, based The Diagnostic System on the idea that mental illness is a mix of things, a natural phenomenon that is influenced by society, strong biological underpinnings and culture. 

He said that diagnosing psychiatric disorders is a highly complex task and might require accepting a kind of fluidity that many people might be uncomfortable with, especially in an era of precision medicine.

As a researcher, Schnittker focuses on the relevance of social factors in shaping health. In the past, he has examined the intersection of genes and environments, as well as the link between being in a prison environment and the health of those people who are currently and formerly incarcerated.