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To understand the importance of the DSM, you have to go back to 1840, when the U.S. first asked in the Census about the frequency of "idiocy/insanity." Those who ran asylums had no standardized way to diagnose patients, which meant their treatments were capricious and occasionally abusive.
In 1917, a group of U.S. psychiatrists persuaded the Census Bureau to gather uniform statistics from mental hospitals. What resulted was a mental-illness section of the American Medical Association's Standard Classified Nomenclature of Disease, which guided psychiatrists in how symptoms clustered to form illnesses. From the beginning, what became the stand-alone book known as the DSM was controversial. The editions published in 1952 and 1980 deepened divisions between Freudians and their rivals, behavior therapists who had absorbed the ideas of Harvard's B.F. Skinner, who believed psychology should be grounded in clinical trials rather than therapy sessions with no definable end points.
All the debates originate from a central problem: we know the basic biology behind, say, leukemia, but we are mostly guessing at the biology of, say, obsessive-compulsive disorder (OCD). For all the magnetic-resonance-imaging tests that tell us which parts of the brain activate during obsessive-compulsive episodes, we are far from a blood test that could separate those with OCD from those who scrub their pots to a gloss when a mere rinse would do.
Over the years, the gray areas have allowed many forces beyond science to shape the DSM, including politics. In 1974, the APA actually held a vote among members to determine whether one alleged disorder--homosexuality--even exists. Being gay was deemed sane by a vote of 5,854 to 3,810, and homosexuality did not appear in the third edition of the DSM, published in 1980.
A Paradigm Shift
In the late '90s, when dsm 5 research began, the success of Prozac and other new drugs led many psychiatrists to believe they might be able to abandon the old diagnostic approach--depression is an abnormal or unconscious reaction to sad situations--for a chemical explanation: depression is a misfiring of neurotransmitters. Many researchers thought psychiatry was on the verge of identifying underlying disease processes--that DSM 5 could codify a paradigm shift, tilting more heavily toward science and away from art.
It didn't turn out that way.
As Columbia University psychiatrist Michael First--an editor of the fourth edition of the DSM--wrote in the November 2010 edition of the Canadian Journal of Psychiatry, "not one single laboratory marker has been shown to be diagnostically useful for making any DSM diagnosis." True, genetic testing can predict a small number of neuropsychological illnesses like Rett's disorder (the emergence of serious movement problems in early childhood). But as for widespread illnesses such as depression or anxiety, multiple studies of twins in the '00s failed to find a distinct genetic basis. And so, as First writes, the core question for clinicians--"whether or not to treat"--won't get much easier after the new book appears.