As the Guide to Mental Ills Is Revised Re "New Guidelines May Sharply Increase Addiction Diagnoses" (news article, May 12): It is an unsubstantiated claim that the proposed changes to substance abuse and dependence disorders in the new Diagnostic and Statistical Manual of Mental Disorders will lead to millions of people being labeled "addicts." In fact, the D.S.M.-5 Work Group's analyses of data from 200,000 people indicate that the minor changes proposed to D.S.M.-5 criteria will not increase the prevalence of substance use disorders. Further input and evaluation from our various review groups, field trials and public comment from our Web site will be assessed before final recommendations are presented to the American Psychiatric Association's board of trustees. These proposed changes combine the D.S.M.-IV categories of substance abuse and substance dependence into D.S.M.-5"s substance use disorder. In this one overarching disorder, the criteria have not only been combined but also strengthened. Previous substance abuse criteria required only one symptom, while the D.S.M.-5"s revised mild substance use disorder (not addiction) requires two to three symptoms. This evidence-based change raises the requirements from D.S.M.-IV rather than broadening them. Like the National Institutes of Health, whose research supports the proposed changes, we are confident that the proposed criteria will lead to improved diagnosis for people seeking help for substance use disorders. The writer, a psychiatrist at the University of Pittsburgh, is chairman of the D.S.M.-5 Task Force. The real issue is that addiction, no matter how it is defined, is vastly underdiagnosed and undertreated in our health care system. Addiction and risky use of tobacco, alcohol and other drugs claim at least 580,000 lives a year, drive 30 percent of national health care spending, and cost each person in America an average of about $1,500 each year. Yearly government spending on substance use and addiction is nearly $500 billion; the tragedy is that only 2 cents of every dollar we spend goes to prevention and treatment. We spend the rest coping with the consequences in our prisons and jails, hospitals, and education and child welfare systems. The real challenge we face is to identify this problem early and get people the help they need to prevent and treat this devastating disease. The writer is president and chief executive of the National Center on Addiction and Substance Abuse at Columbia University. Allen Frances ("Diagnosing the D.S.M.," Op-Ed, May 12) has it exactly right. All mental health disciplines need to be represented in this dialogue, and there needs to be some way of preventing unqualified doctors from prescribing psychiatric medications. For years people have shown up for therapy wrongly or overly medicated by general practitioners or even dentists who have taken self-reported symptoms, looked them up in the mental disorders manual, and irresponsibly written a prescription instead of referring the patient to a psychiatrist. This includes parents who report having a child receive a diagnosis of a learning disability, attention deficit disorder or autism from a school counselor who looked it up in the diagnostic manual. If all disciplines are included in creating the diagnostic criteria, perhaps patients will receive correct diagnoses and be treated with much more accuracy. The writer is a psychologist.