The Toll Personality disorders afflict at least 31 million Americans -- nearly 15 percent of adults -- according to a study in the July issue of Journal of Clinical Psychiatry, the first study to measure the prevalence of a constellation of mental illnesses that includes dependent and antisocial personality disorders.

Back Story Previously known as character disorders because they reflect pervasive, inflexible, distressing and maladaptive patterns of behavior, diagnosable personality problems typically surface in adolescence or early adulthood and tend to be resistant to treatment. Many sufferers also abuse alcohol or drugs. These problems have received little attention from epidemiologists, who have focused on measuring other psychiatric disorders such as depression.

Count Down Researchers at the National Institute on Alcohol Abuse and Alcoholism (NIAAA) examined data from the agency's survey of 43,000 adults conducted in 2001 and 2002 to determine how many met the criteria for seven of the 10 personality disorders described in the Diagnostic and Statistical Manual IV, the standard reference for mental disorders. The seven disorders included obsessive-compulsive personality disorder (think "perfectionist control freak"), as well as avoidant, antisocial, dependent and paranoid personality disorders.

His and Hers Some personality problems (avoidant, dependent and paranoid) were more common in women, while those with antisocial personality were usually men. There was no sex difference for the most common disorder -- obsessive-compulsive -- and one of the least common -- histrionic personality, the hallmark of which is excessive emotional displays.

"We never knew how common personality disorders are because it's never been measured," said lead author Bridget F. Grant, chief of the epidemiology and biometry lab at NIAAA. "I certainly never expected it to be that large."

-- Sandra G. Boodman