What's the world's most widely used classification system for mental disorders? If you guessed the Diagnostic and Statistical Manual of Mental Disorders (DSM), you would be wrong.

According to a study of nearly 5,000 psychiatrists in 44 countries sponsored by the World Health Organization (WHO) and the World Psychiatric Association, more than 70 percent of the world's psychiatrists use WHO's International Classification of Diseases (ICD) most in day-to-day practice while just 23 percent turn to the DSM. The same pattern is found among psychologists globally, according to preliminary results from a similar survey of international psychologists conducted by WHO and the International Union of Psychological Science.

"The ICD is the global standard for health information," says psychologist Geoffrey M. Reed, PhD, senior project officer in WHO's Department of Mental Health and Substance Abuse. "It's developed as a tool for the public good; it's not the property of a particular profession or particular professional organization."

Now WHO is revising the ICD, with the ICD-11 due to be approved in 2015. With unprecedented input from psychologists, the revised version's section on mental and behavioral disorders is expected to be more psychologist-friendly than ever—something that's especially welcome given concerns being raised about the DSM's own ongoing revision process. (See "Protesting proposed changes to the DSM".) And coming changes in the United States will mean that psychologists will soon need to get as familiar with the ICD as their colleagues around the world.

The ICD revision process

Encompassing both mental and physical disorders, the ICD classification system assigns codes used for health statistics, reimbursement systems and other purposes. The current version, the ICD-10, was published in 1992.

The ICD-11 will see major changes, predicts Reed, who is coordinating revisions to its mental and behavioral disorders section and participating in revisions to the section on nervous system diseases. That's due in part to the fact that it's not just psychiatrists revising the relevant sections anymore. For the first time, psychologists and other mental health professionals are also integrally involved (see "Defining disease worldwide," July/August 2010 Monitor).

The result, Reed predicts, is that the publication "will be written from a more behavioral perspective, not only from a medical perspective."

Psychologists from around the world are formally participating in the effort. Some are serving on the international advisory groups for the mental and behavioral disorders and diseases of the nervous system sections. Others are participating in working groups focused on specific populations or types of disorders, such as mood and anxiety disorders, neurocognitive disorders and children and adolescents.

APA Board Member Nadine J. Kaslow, PhD, of Emory University School of Medicine, has been working with an international group of psychologists, psychiatrists and other mental health professionals to ensure that the ICD-11 gives more attention to interpersonal factors that may affect both mental and physical health.

Kaslow cites as an example the difference between having a broken arm because your parents beat you up versus having one because you were playing soccer, fell down and hurt yourself. The same goes for mental health diagnoses.

"Clearly, having information on relationship context can make a big difference in the types of interventions people consider for a particular problem," says Kaslow. "And greater attention to relationship context has the potential to improve prevention as well as treatment efforts."

Making the ICD easier to use is another goal. That's especially important since most people worldwide who need mental health treatment will never see a mental health professional, simply because specialists are not available. "The field is telling us that the classification should be simplified substantially," says Reed. In the survey of psychiatrists, he points out, more than 85 percent thought there should be fewer than 100 diagnostic categories.

The personality disorders section is one that's likely to be simplified, says Reed, explaining that the ICD-10 includes many separate types of personality disorders. The psychologists and other members of the working group tackling this section believe that what's most helpful in determining treatment is not the specific kind of disorder an individual has but how severe that disorder is. As a result, the working group proposes to restructure the section to emphasize severity, with information on subtypes available if users want it.

The new version will also draw on research about how clinicians conceptualize mental disorders in hopes of creating a more intuitive classification system. Two large studies by WHO have found what Reed calls "an astonishing level of consistency" in the way clinicians around the world mentally organize mental disorders. And the way they conceptualize disorders isn't the same way existing classification systems do, he adds.

The ICD will also be easy to get, adds Reed. In addition to the usual printed version, which will be inexpensive and available at even lower cost to low- and middle-income countries, the ICD-11 will be available for free on the Internet.

A broader perspective

While most U.S. psychologists use the DSM to make diagnoses, those working in neuropsychology, rehabilitation and other health settings not strictly devoted to mental health services are already familiar with the ICD, says APA President Suzanne Bennett Johnson, PhD, a research professor in the medical humanities and social sciences department at Florida State University.

As a psychologist in a health center, Johnson is one of them.

"The reality is that we are, and need to act as, a member of the worldwide community," she says. "We should be part of that worldwide effort to address human health and not just be doing our own thing here in the U.S., using a different code than other people."

The ICD also helps to integrate psychology into the larger health-care delivery system, says Johnson. While the DSM encourages mind/body dualism, she says, the ICD allows psychologists to recognize mind/body connections. When Johnson sees a child with diabetes, for example, she's able to use a Type-1 diabetes code rather than a code for a mental health disorder. "The ICD opens up a whole world where we can provide services to all kinds of patients, including those with mental disorders," she says.

The ICD is also a boon to researchers, adds Johnson. "If you want to make any comparisons between countries in terms of mental health burden or anything else, you need a common diagnostic system," she says.

Coming changes

Johnson can foresee a day when U.S. psychologists will no longer need the DSM. And that transition is about to begin, she says.

Most insurers already use ICD codes, she points out. That's because the Health Insurance Accountability and Portability Act of 1996 requires the use of ICD codes as a diagnostic standard. When a clinician submits a DSM diagnostic code, a professional coder or the insurer then translates it into an ICD code. Sometimes psychologists use software that "crosswalks" the codes so they can do the translation themselves.

Translating from DSM codes to ICD codes isn't that big a deal right now, says Lynn Bufka, PhD, assistant executive director for practice research and policy in APA's Practice Directorate. That's because while other countries are currently using the ICD-10, the United States is still using the ICD-9. And the ICD-9-CM—the version clinically modified by the Centers for Disease Control and Prevention for use in the United State—and the DSM IV are very similar.

"Technically, psychologists are already using the ICD when they're submitting billing," says Bufka. "But most psychologists aren't aware that they are because the two systems have been harmonized."

Beginning in October 2013, however, U.S. practitioners will be required to use the ICD-10-CM, which differs significantly from the DSM. According to Reed, both codes and the organization of chapters will be different.

Since the rest of the world will be adopting the ICD-11 when it is released in 2015, the CDC will likely make annual updates to gradually bring the ICD-10-CM into line with the ICD-11 to avoid another abrupt shift. But the differences between the DSM and the ICD may grow even greater over time, says Reed, depending on the outcomes of the ICD and DSM revision processes.

While APA supports the shift to the ICD-10-CM, there is some resistance to it. The American Medical Association's House of Delegates has voted to work to stop the transition, citing financial and practical concerns—the same justifications used to stop the ICD-10's adoption two decades ago even as the rest of the world embraced the updated code set.

Reed doesn't think learning the new system will be that difficult. And APA is already making plans to help ensure that psychologists are prepared for the change.

Reed will present a "Clinician's Corner" workshop on the ICD at APA headquarters from 1 to 4 p.m. ET on April 12. (Visit APA's Continuing Education in Psychology for more details or to register.) The presentation will be webcast nationally and then become available on demand on APA's website, says Greg J. Neimeyer, PhD, director of APA's Office of Continuing Education in Psychology. "He's going to basically try to frame up what the ICD will look like when it hits North America next year and help psychologists transition to it," he says, adding that the target audience is both practitioners and researchers.

Reed will also lead two programs at APA's 2012 Annual Convention in Orlando in August. One will be a symposium as part of Johnson's presidential programming; another will be a half-day workshop focused on practical applications of the ICD. "All these events are designed to reach the same audience from multiple perspectives," says Neimeyer.

For more information about the ICD revision, visit the World Health Organization.

Rebecca A. Clay is a writer in Washington, D.C.