Daily news reports on the havoc caused by roadside bombs in Iraq have made the initials IED (short for improvised explosive device) familiar to many Americans. Now a recently released medical study has brought to the public's attention another meaning for IED-intermittent explosive disorder-and its manifestation at times in the form of road rage.

The disorder known as IED is attributed to the inadequate production or delivery of the mood-regulating chemical serotonin and may affect as many as 16 million Americans, or 5 to 7 percent of the population, far more than previously thought, according to Ronald Kessler,PhD, a health care professor at Harvard Medical School and lead author of the study. Funded by the National Institute of Mental Health, the study's researchers say IED is marked by "irrational, sudden and uncontrollable anger grossly out of proportion to any precipitating psychosocial stressor," with individuals often smashing property or hitting people.

Although it has been used as a successful legal defense, IED is not accepted by all medical professionals as a bona fide disorder.

Responding to the study, AAA's manager of driver training operations, William Van Tassel, PhD, cautions that IED "is a form of impairment, like DWI or the lack of sleep," for which the driver is responsible. "Driving is a mental task-if you're not fit to drive, you should not be driving."

Advice on how to avoid becoming a target of road rage and reducing one's own stress while driving is included in AAA New York's Driver Anger Management workshop and in its six-hour Driver Improvement Program. For more information on this and other workshops, contact Barbara Ward at 516/873-2378 or Ed Welsh at 315/624-3901.