It can fairly be said that modern psychiatric diagnosis was “born” in a 1970 paper on schizophrenia.
The authors, Washington University psychiatry professors Eli Robins and Samuel B. Guze, rejected the murky psychoanalytic diagnostic formulations of their time. Instead, they embraced a medical model inspired by the careful 19th-century observational work of Emil Kraepelin, long overlooked during the mid-20th-century dominance of Freudian theory. Mental disorders were now to be seen as distinct categories, much as different bacterial and viral infections produce characteristic diseases that can be seen as distinct “natural kinds.”
Disorders, Robins and Guze argued, should be defined based on phenomenology: clinical descriptions validated by long-term follow-up to demonstrate the stability of the diagnosis over time. With scientific progress, they expected fuller validation of mental disorders to derive from laboratory findings and studies of familial transmission.
This descriptive approach to psychiatric diagnosis -- based on lists of symptoms, their timing of onset, and the duration of illness -- undergirded the American Psychiatric Association’s widely disseminated and highly influential Diagnostic and Statistical Manual of Mental Disorders, first published in 1980. Since then, the original “DSM-III” has yielded two relatively conservative revisions, and right now, the DSM-5 is under construction. Sadly, it is clear that the optimistic predictions of Robins and Guze have not been realized.
Four decades after their seminal paper, there are still no widely validated laboratory tests for any common mental illness. Worse, an enormous number of family and genetic studies have not only failed to validate the major DSM disorders as natural kinds, but instead have suggested that they are more akin to chimaeras. Unfortunately for the multitudes stricken with mental illness, the brain has not given up its secrets easily.
That is not to say that we have made no progress. DNA research has begun to illuminate the complex genetics of mental illness. But what it tells us, I would argue, is that, at least for the purposes of research, the current DSM diagnoses do not work. They are too narrow, too rigid, altogether too limited. Reorganization of the DSM is hardly a panacea, but science cannot thrive if investigators are forced into a cognitive straitjacket.
Before turning to the scientific evidence of fundamental problems with the DSM, let’s first take note of an important problem that the classification has produced for clinicians and patients alike: An individual who receives a single DSM diagnosis very often meets criteria for multiple additional diagnoses (so-called co-occurrence or “comorbidity”), and the pattern of diagnoses often changes over the lifespan. Thus, for example, children and adolescents with a diagnosis of an anxiety disorder often manifest major depression in their later teens or twenties. Individuals with autism spectrum disorders often receive additional diagnoses of attention deficit hyperactivity disorder, obsessive-compulsive disorder, and tic disorders.
Of course, there are perfectly reasonable explanations for comorbidity. One disorder could be a risk factor for another just as tobacco smoking is a risk factor for lung cancer. Alternatively, common diseases in a population could co-occur at random. The problem with the DSM is that many diagnoses co-occur at frequencies far higher than predicted by their population prevalence, and the timing of co-occurrence suggests that one disorder is not likely to be causing the second. For patients, it can be confusing and demoralizing to receive multiple and shifting diagnoses; this phenomenon certainly does not increase confidence in their caregivers.
Family studies and genetics shed light on the apparently high rate of co-occurrence of mental disorders and suggest that it is an artifact of the DSM itself. Genetic studies focused on finding variations in DNA sequences associated with mental disorders have repeatedly found shared genetic risks for both schizophrenia and bipolar disorder. Other studies have found different sequence variations within the same genes to be associated with schizophrenia and autism spectrum disorders.