Of course, doctors in other specialties face time constraints and other threats to accurate diagnosis. But unlike psychiatrists, they usually have a molecular definition of disease to go on and biological tests to administer. The current lack of molecular knowledge in psychiatry is no fault of psychiatrists; the human brain is complex and difficult to experiment on. But it cannot be denied that the DSM is not a collection of diseases so much as syndromes—groupings of symptoms that may have many different molecular causes. Because the molecular causes are largely unknown, biological tests don't exist, and a psychiatrist making a diagnosis is left without the lab results that in other areas of medicine help correct doctors' subjective impressions.
This may change. Last November, several researchers reported the creation of a computer algorithm that can differentiate, with 81 percent accuracy, the MRI images of schizophrenic brains compared with healthy ones. And some clinical trials have already begun to track how the presence of certain genes influences a patient's response to medication. The cost of sequencing a patient's genome has dropped by a thousandfold in the last five years, so genetically based psychiatric studies should soon become commonplace.
None of this means that psychiatrists will develop a magic diagnostic test, though. After all, genes only tell you so much. There are, for example, many genes implicated in schizophrenia, and a genetic predisposition does not guarantee illness. (If one identical twin gets schizophrenia, there is a 50 percent chance the other one will.) Even a brain scan isn't clear-cut. For example, many healthy family members of schizophrenics have been found to have subtle schizophrenic symptoms. If an entire family were to show different degrees of the illness on an MRI, establishing who gets an official diagnosis and who does not would still be a matter of judgment.
The Rosenhan study, which is still mentioned in undergraduate textbooks, continues to be an albatross for psychiatry. Working with the tools available to his generation of psychiatrists, Spitzer has done his best to put the profession on a scientific footing. But the psychiatrists who will integrate psychiatry into medicine—by finally linking the study of the mind to the study of the brain—have just begun to get to work.