Where does psychological health end and mental illness begin? This is the question that Richard J. McNally, a Harvard psychologist, asks in his new book. Should we worry about the sanity of the author for assigning himself this thankless task? He might as well be asking where to draw the line between twilight and dusk. But rest assured: McNally’s wide-ranging and extremely readable book is quite sane, and vastly illuminating. Rather than answer the question directly, it appraises current attempts by psychiatrists, philosophers of science, evolutionary biologists, and neuroscientists to clarify the boundary between mental disorder and mental distress.
Early in the book, McNally describes himself as a friendly critic of psychiatry. He is an insider, having served on the American Psychiatric Association’s DSM-IV PTSD and various phobia committees, and as an advisor to the DSM-5 Anxiety Disorders Sub-Work Group. "I am not a DSM basher," he writes, "I am keen to make constructive suggestions about the direction of the field and how we treat and understand mental disorders." He does so by rooting out bad theories.
There is in fact a powerful reason to scrutinize the field: we are in the midst of a mental illness epidemic. Office visits by children and adolescents treated for the condition jumped forty-fold from 1994 to 2003. According to the National Institute of Mental Health, nearly half of all Americans have suffered from mental illness—depression, anxiety, even psychosis—at some time in their lives. Is one out of every two Americans mentally ill, or could it be that the system of psychiatric diagnosis too often mistakes the emotional problems of everyday life for psychopathology?
This system is codified in the Diagnostic and Statistical Manual of Mental Disorders, the official handbook of the American Psychiatric Association. Now in its fourth edition, the psychiatric bible, as it is sometimes called, spells out the criteria for over 360 different diagnoses. The DSM serves as the basic text for training practitioners, for insurance companies who rely on it to determine coverage, for social service agencies who use it to assess disabilities, and for the courts, which turn to it to resolve questions of criminal culpability, competence to stand trial, and insanity.
Despite the vast influence of DSM and the best efforts of its architects, the manual has failed to clear up the murky border between health and sickness. Two examiners may concur that a person qualifies for a particular diagnosis, but this does not always mean that she has an authentic mental illness. How do we know that a patient is suffering from major depressive disorder, the DSM’s formal designation for pathological depression? It could be that she is not mentally ill, but is going through a bout of natural sadness brought on by a devastating disappointment or a grave medical illness. It is arguably too easy to pathologize everyday life. Just think of such misery-inducing and potentially disabling conditions, as post traumatic stress disorder, social anxiety disorder, and sexual dysfunction—all considered forms of mental illness by the DSM, and rightly so, but all too inclusive as well.
So how to clear up the fog? Some scholars believe that evolutionary psychology can increase understanding of the origins of psychopathology and thus sharpen our diagnoses. McNally describes the newly popular idea that mental illness is good for the species. He then shoots this theory down by pointing out that authentic mental illnesses are not only devoid of benefit, but they can also be downright damaging because they constrain reproductive fitness. In the type of edifying dialectic that readers interested in the philosophy of medicine will savor, McNally next addresses the intriguing question of why natural selection has not eliminated the genetic variants that predispose people to mental illness. The answer is that there are scores of genes that contribute to mental illnesses—making it hard to bring selection pressure to bear upon a specific culprit.
McNally also describes some fascinating findings on the interaction between genes and environment. This is a vibrant field of inquiry, to be sure, but it has yet to produce many clinical applications. And what about neuroscience? Alas, McNally says, we are not yet in a position to understand mental illness "in terms of abnormalities in the structure and function of the brain [though neuroscientists] are paving the way for a more etiologically informed nosology in the future." (Nosology is the science of disease classification.)
Still, McNally offers a handful of suggestions to help make diagnosis conform more closely to clinical reality. He recommends, for example, that personality disorders no longer be identified as ten discrete categories (borderline personality disorder, antisocial personality disorder, narcissistic personality disorder, schizoid, and so on). Such divisions, he argues, are too sloppy. Many patients meet the criteria for more than one category because there is overlap in the symptoms. What’s more, individuals assigned to a given category sometimes exhibit wildly different behaviors.
As a possible remedy, McNally endorses a so-called "dimensional" approach to describing personality traits. Instead of discrete categories, a patient’s personality structure would be described as a constellation of her normal adaptive traits as well as her maladaptive traits. The latter would be scored for severity on five major dimensions—extraversion-to-introversion, neuroticism-to-emotional-stability, and so on. Early studies suggest that personality "scores" based on these dimensions are better able to make clean distinctions among abnormal personality types than the defined categories currently in the DSM.
McNally’s major point is that science is merely one factor in resolving disputes at the border of illness and health. "Because the boundary between the two is a fuzzy one, social, political, and economic factors often prove decisive when it comes to deciding whether ambiguous cases count as mental illness or mental disorder," he writes. It is easy to see how. "There is money in madness," he jokes. But ideally, McNally believes, science will likely get much better at discovering what has gone wrong with a person and do what really counts for patients and doctors: inform us about what treatments will work best. These facts will provide the basis for sound arguments about where to draw the boundary between distress and disorder, even though social factors will always play a role.
Perhaps the most profound insight in What is Mental Illness? has to do with the role of culture. McNally presents a clinically nuanced, historically rich, and anthropologically informed discussion of how mental illnesses are expressed. He highlights two general classes of psychic illness: "natural kinds" and "interactive kinds." Some natural syndromes, he explains, are likely discovered by observant clinicians across cultures or throughout history. Mania, schizophrenia, panic disorder, and obsessive compulsive disorder offer classic examples. "The core of these syndromes is largely indifferent to cultural influence," he writes. Remarkably, schizophrenia seems to have appeared de novo in the early 1800s, perhaps a result of an infectious agent.
By contrast, culture penetrates more deeply into other conditions: "In the case of bulimia nervosa, mental representations of thinness as an ideal body shape, absorbed from the ambient culture, interact with vulnerabilities such as difficulty regulating one’s emotions to incite the cycle of dieting, binging, and purging." McNally also points to the very real suffering of people with post-traumatic stress disorder, but acknowledges that the way they understand their condition—as a chronic, relapsing disorder, as opposed to an illness from which they can recover—can affect their progress. Multiple personality disorder lies at the far end of the natural versus interactive continuum, because it is almost entirely socially constructed. Citing scholarly detective work, he debunks the myth of "Sybil," the most famous multiple of modern time, as a woman who was never abused, though her story launched an epidemic of multiple personality disorder overnight.
The next DSM edition, the fifth, is now in the works. To judge by the heated controversy within academic and advocacy circles generated by interim progress reports, its unveiling in 2013 will doubtless shine an uncomfortable spotlight on the psychiatric profession and spark plenty of debate. McNally’s masterful synthesis will help us understand the discussion, and thereby help us to understand ourselves.
Sally Satel is a resident scholar at AEI.